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Preview: Journal of Antimicrobial Chemotherapy - current issue

Journal of Antimicrobial Chemotherapy - current issue



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40 years of veterinary papers in JAC - what have we learnt?

2016-09-22T00:05:52-07:00

This review, for the occasion of the 40th anniversary of the Journal of Antimicrobial Chemotherapy (JAC), gives an overview of the manuscripts related to veterinary bacteriology published in the journal in the past 40 years with a focus on ‘One Health’ aspects. From 1975 to 2000 the number of manuscripts related to veterinary medicine was limited, but thereafter, the number steadily increased. Most manuscripts published were related to food-producing animals, but companion animals and minor species were also covered. Subjects included antimicrobial usage in animals and the consequences for human medicine, new resistance genes and mechanisms, the prevalence and epidemiology of antimicrobial resistance, and the emergence of resistant bacteria in animals with zoonotic potential such as livestock-associated MRSA (LA-MRSA), methicillin-resistant Staphylococcus pseudintermedius (MRSP) and ESBL-producing Enterobacteriaceae. These manuscripts have added to our knowledge on the risks of transmission of resistant bacteria from animals to humans and the importance of the prudent use of antimicrobial agents in veterinary medicine.




Pharmacokinetic/pharmacodynamic-based optimization of levofloxacin administration in the treatment of MDR-TB

2016-09-22T00:05:52-07:00

The emergence of MDR-TB and XDR-TB has complicated TB treatment success. Among many factors that contribute to the development of resistance, low drug exposure is not the least important. This review summarizes the available information on pharmacokinetic properties of levofloxacin in relation to microbial susceptibilities, in order to optimize the dose and make general treatment recommendations. A total of 37 studies on adult (32 studies) and paediatric (5 studies) MDR-TB patients were included. Among the 32 adult studies, 19 were on susceptibility of Mycobacterium tuberculosis isolates to levofloxacin by MIC, 1 was on susceptibility of M. tuberculosis isolates to levofloxacin by MBC, 1 was on susceptibility of M. tuberculosis isolates to levofloxacin by mutant prevention concentration and 4 were on pharmacokinetics of levofloxacin, and 7 others were included. Likewise, out of five studies on children, two dealt with levofloxacin pharmacokinetic parameters, one reviewed CSF concentrations and two dealt with background information. In adult MDR-TB patients, standard dosing of once-daily 1000 mg levofloxacin in TB treatment did not consistently attain the target concentration (i.e. fAUC/MIC >100 and fAUC/MBC >100) in 80% of the patients with MIC and MBC of 1 mg/L, leaving them at risk of developing drug resistance. However, with an MIC of 0.5 mg/L, 100% of the patients achieved the target concentration. Similarly, paediatric patients failed consistently in achieving given pharmacokinetic/pharmacodynamic targets due to age-related differences, demanding a shift towards once daily dosing of 15–20 mg/kg. Therefore, we recommend therapeutic drug monitoring for patients with strains having MICs of ≥0.5 mg/L and suggest revising the cut-off value from 2 to 1 mg/L.




A review of the pharmacokinetics and pharmacodynamics of aztreonam

2016-09-22T00:05:52-07:00

The monobactam aztreonam is currently being re-examined as a therapeutic agent in light of the global spread of carbapenem resistance in aerobic Gram-negative bacilli and aztreonam's stability to Ambler class B metallo-β-lactamases. Of particular interest are the pharmacokinetic and pharmacodynamic properties of aztreonam alone and in combination with β-lactamase inhibitors. The choice of inhibitor may vary depending on the spectrum of β-lactamases produced by Enterobacteriaceae. The monobactam ring is also being used to produce new developmental monobactams. Thus, a greater understanding of aztreonam pharmacokinetics and dynamics is of great relevance in drug development. This review summarizes the pharmacokinetic profile of aztreonam in man and its pharmacodynamics in human and pre-clinical studies when studied alone and with β-lactamase inhibitors.




Spotlight on ceftazidime/avibactam: a new option for MDR Gram-negative infections

2016-09-22T00:05:52-07:00

During the last decade infections caused by MDR Gram-negative bacteria (GNB) have become increasingly prevalent. Because of their high morbidity and mortality rates, these infections constitute a serious threat to public health worldwide. Ceftazidime/avibactam is a new approved agent combining ceftazidime and a novel β-lactamase inhibitor with activity against various β-lactamases produced by MDR GNB. Avibactam has a spectrum of inhibition of class A and C β-lactamases, including ESBLs, AmpC and Klebsiella pneumoniae carbapenemase (KPC) enzymes. Thus, combination with this inhibitor expands ceftazidime's spectrum of activity to MDR Enterobacteriaceae and Pseudomonas aeruginosa strains. In Phase II clinical trials of patients with complicated intra-abdominal infections and complicated urinary tract infections ceftazidime/avibactam exhibited clinical efficacy comparable to those of meropenem and imipenem/cilastatin, respectively. A Phase III clinical trial confirmed the efficacy of ceftazidime/avibactam in patients with MDR Enterobacteriaceae and P. aeruginosa infections. Microbiological surveillance studies, in vivo animal models of infection and pharmacokinetic/pharmacodynamic target attainment analyses are also discussed, to assess the potential role of this new drug in the treatment of infections caused by MDR GNB.




Antimicrobial resistance surveillance in urinary tract infections in primary care

2016-09-22T00:05:52-07:00

Urinary tract infection (UTI) is one of the most common reasons for prescription of antimicrobials in primary care. Laboratory resistance data produced because of specimen analysis to support individual patient diagnosis and management are generalized to guide empirical therapy across a wider population, but are limited by bias toward certain patient groups and almost certainly overestimate the incidence of resistance. Other methods of surveillance are required to provide unbiased estimates of antimicrobial resistance, but need to be sustainable. Sentinel surveillance, perineal flora sampling and development of clinical algorithms to support more stratified and personalized antimicrobial prescribing need to be further investigated. Linkages to prescription and clinical outcome data are essential if the burden of antimicrobial resistance in UTI is to be understood. Pilot and feasibility studies need to be performed to establish the best approach to enhancing the quality, relevance and sustainability of antimicrobial resistance surveillance in community-acquired UTI.




Natural history and decolonization strategies for ESBL/carbapenem-resistant Enterobacteriaceae carriage: systematic review and meta-analysis

2016-09-22T00:05:52-07:00

Background

ESBL-producing Enterobacteriaceae and carbapenem-resistant Enterobacteriaceae (CRE) are rapidly spreading worldwide. Their natural reservoir is intestinal.

Methods

We carried out a systematic review and meta-analysis to estimate CRE and ESBL carriage duration and to evaluate the effect of decolonization therapy. We included cohort and comparative studies examining the natural history of CRE/ESBL colonization, examining rates of carriage following decolonization or comparing decolonization and no decolonization conducted in the healthcare setting or in the community. A comprehensive search was conducted until November 2015. We compiled carriage rates at 1, 3, 6 and 12 months with and without decolonization therapy and assessed the effect of decolonization.

Results

Thirty-seven studies fulfilled inclusion criteria. In healthcare settings, pooled ESBL/CRE colonization rates decreased without intervention from 76.7% (95% CI = 69.3%–82.8%) at 1 month to 35.2% (95% CI = 28.2%–42.9%) at 12 months of follow-up. Following decolonization, the rate was 37.1% (95% CI = 27.5%–47.7%) at end of therapy and 57.9% (95% CI = 43.1%–71.4%) at 1 month. In two randomized trials, carriage was significantly reduced at end of therapy (risk ratio = 0.42, 95% CI = 0.25–0.65), but the effect was not significant after 1 month (risk ratio = 0.72, 95% CI = 0.48–1.05), with no longer follow-up. Heterogeneity was explained by surveillance methodology, with no differences observed between ESBLs and CREs. Among community dwellers, ESBL colonization decreased from 52.3% (95% CI = 29.5%–74.2%) at 1 month to 19.2% (95% CI = 9.7%–34.4%) at 6 months.

Conclusions

A significant proportion of ESBL and CRE carriers remain colonized up to 1 year in the healthcare setting. While short-term decolonization therapy reduces carriage during therapy, its longer-term effects are unclear.




Systematic review and meta-analysis: triple therapy combining a proton-pump inhibitor, amoxicillin and metronidazole for Helicobacter pylori first-line treatment

2016-09-22T00:05:52-07:00

Background

Due to clarithromycin resistance, the current efficacy of Helicobacter pylori first-line triple therapies including clarithromycin is low. It seems reasonable to explore alternative clarithromycin-free therapies.

Objectives

The objective of this study was to evaluate the efficacy of triple therapy including a proton-pump inhibitor (PPI), amoxicillin and metronidazole (PAM) as first-line H. pylori therapy by systematic review and meta-analysis.

Methods

Studies evaluating PAM in adult patients were included. Meta-analyses comparing PAM with other treatments were performed. The primary endpoint was the ITT eradication rate for H. pylori first-line treatment. In addition, sensitivity analyses ascertained the effects of treatment schedule, dosage and duration on cure rates.

Results

Ninety-four studies (8061 patients) were included. Meta-analyses comparing PAM versus clarithromycin-including triple therapies showed a significant difference in favour of PPI, amoxicillin and clarithromycin (PAC) (70% versus 77.1%; OR = 0.70, 95% CI = 0.56–0.88) and PPI, metronidazole and clarithromycin (PMC) therapy (66.4% versus 77.7%; OR = 0.55, 95% CI = 0.39–0.76). Sensitivity analyses showed a similar efficacy of PAM versus PAC when drugs were administered for 14 days (80% versus 84%; OR = 0.70, 95% CI = 0.44–1.12). There were not enough studies to perform further comparisons. Number of antibiotic doses (P = 0.012), length of treatment (P < 0.001) and use of high metronidazole doses (P = 0.021) were related to higher cure rates in the sensitivity analysis including observational studies.

Conclusions

PAM was less efficacious than clarithromycin-including triple therapies. However, its efficacy was similar to that of PAC when drugs were administered for 14 days, although ITT cure rates did not reach 90%. Use of 14 day, thrice daily and high-metronidazole-dose PAM treatments markedly increased the cure rate.




Amikacin use and therapeutic drug monitoring in adults: do dose regimens and drug exposures affect either outcome or adverse events? A systematic review

2016-09-22T00:05:52-07:00

Objectives

The objectives of this study were to identify the amikacin dosage regimens and drug concentrations consistent with good outcomes and to determine the drug exposures related to nephrotoxicity and ototoxicity.

Methods

A literature review was conducted in Medline, EMBASE and the Cochrane Central Register of Controlled Trials. Full journal articles reporting randomized controlled trials, controlled clinical trials, interrupted time series trials, and controlled before and after studies involving amikacin therapeutic drug monitoring (TDM) and dose adjustment were considered for inclusion.

Results

Seventeen studies for inclusion were identified, comprising 1677 participants. Amikacin doses ranged from 11 to 15 mg/kg/day with 13 studies using 15 mg/kg/day. Studies were generally designed to compare different aminoglycosides rather than to assess concentration–effect relationships. Only 11 papers presented data on target concentrations, rate of clinical cure and toxicity. Target peak concentrations ranged from 15 to 40 mg/L and target troughs were typically <10 or <5 mg/L. It was not clear whether these targets were achieved. Measured peaks averaged 28 mg/L for twice-daily dosing and 40–45 mg/L for once-daily dosing; troughs averaged 5 and 1-2 mg/L, respectively. Fifteen of the included studies reported rates of nephrotoxicity; auditory and vestibular toxicities were reported in 12 and 8 studies.

Conclusions

This systematic review found little published evidence to support an optimal dosage regimen or TDM targets for amikacin therapy. The use of alternative approaches, such as consensus opinion and a review of current practice, will be required to develop guidelines to maximize therapeutic outcomes and minimize toxicity with amikacin.




Rilpivirine resistance mutation E138K in HIV-1 reverse transcriptase predisposed by prevalent polymorphic mutations

2016-09-22T00:05:52-07:00

Background

Rilpivirine is listed as a recommended or alternative key drug in the current ART guidelines. E138K in HIV-1 reverse transcriptase (RT) is a primary mutation in resistance to rilpivirine, although in vitro experiments showed it confers only <3-fold resistance. An unidentified mechanism could amplify resistance to rilpivirine conferred by E138K.

Objectives

The objective of this study was to reveal the mechanism amplifying rilpivirine resistance conferred by E138K.

Patients and methods

HIV-1 RT sequences were compared in patients who failed rilpivirine-containing ART virologically. The effects of mutations commonly identified with E138K on rilpivirine susceptibility were analysed by using recombinant HIV-1 variants.

Results

Rilpivirine-containing ART was introduced in 162 HIV-1-infected patients at the outpatient clinic of the AIDS Clinical Center (National Center for Global Health and Medicine, Tokyo, Japan) between May 2012 and June 2015. Virological treatment failure occurred in six of these patients. E138K emerged in three patients while other rilpivirine resistance mutations emerged in the other three patients. I135T/L were identified in only three patients with E138K and existed before the introduction of rilpivirine-containing ART. Analysis of recombinant HIV-1 variants indicated that E138K conferred low-level rilpivirine resistance and that coexistence of I135T/L with E138K amplified the resistance.

Conclusions

I135T/L, escape mutations from HLA-B*51/52-restricted cytotoxic T lymphocytes, which are prevalent in Japan, may predispose HIV-1 to harbour E138K upon failure of rilpivirine-containing ART. The mutation patterns of drug resistance may vary due to baseline polymorphic mutations.




Identification of novel macrolides with antibacterial, anti-inflammatory and type I and III IFN-augmenting activity in airway epithelium

2016-09-22T00:05:52-07:00

Background

Exacerbations of asthma and COPD are triggered by rhinoviruses. Uncontrolled inflammatory pathways, pathogenic bacterial burden and impaired antiviral immunity are thought to be important factors in disease severity and duration. Macrolides including azithromycin are often used to treat the above diseases, but exhibit variable levels of efficacy. Inhaled corticosteroids are also readily used in treatment, but may lack specificity. Ideally, new treatment alternatives should suppress unwanted inflammation, but spare beneficial antiviral immunity.

Methods

In the present study, we screened 225 novel macrolides and tested them for enhanced antiviral activity against rhinovirus, as well as anti-inflammatory activity and activity against Gram-positive and Gram-negative bacteria. Primary bronchial epithelial cells were grown from 10 asthmatic individuals and the effects of macrolides on rhinovirus replication were also examined. Another 30 structurally similar macrolides were also examined.

Results

The oleandomycin derivative Mac5, compared with azithromycin, showed superior induction (up to 5-fold, EC50 = 5–11 μM) of rhinovirus-induced type I IFNβ, type III IFN1 and type III IFN2/3 mRNA and the IFN-stimulated genes viperin and MxA, yet had no effect on IL-6 and IL-8 mRNA. Mac5 also suppressed rhinovirus replication at 48 h, proving antiviral activity. Mac5 showed antibacterial activity against Gram-positive Streptococcus pneumoniae; however, it did not have any antibacterial properties compared with azithromycin when used against Gram-negative Escherichia coli (as a model organism) and also the respiratory pathogens Pseudomonas aeruginosa and non-typeable Haemophilus influenzae. Further non-toxic Mac5 derivatives were identified with various anti-inflammatory, antiviral and antibacterial activities.

Conclusions

The data support the idea that macrolides have antiviral properties through a mechanism that is yet to be ascertained. We also provide evidence that macrolides can be developed with anti-inflammatory, antibacterial and antiviral activity and show surprising versatility depending on the clinical need.




P-glycoprotein (ABCB1) activity decreases raltegravir disposition in primary CD4+P-gphigh cells and correlates with HIV-1 viral load

2016-09-22T00:05:52-07:00

Objectives

To evaluate the role of P-glycoprotein (P-gp) and multidrug-resistant-protein 1 (MRP1) on raltegravir intracellular drug disposition in CD4+ T cells, investigate the effect of HIV-1 infection on P-gp expression and correlate HIV-1 viraemia with P-gp activity in primary CD4+ T cell subsets.

Methods

The cellular accumulation ratio of [3H]raltegravir was quantified in CD4+ T cell lines overexpressing either P-gp (CEM-P-gp) or MRP1 (CEM-MRP1) and in primary CD3+CD4+ T cells with high (P-gphigh) and low P-gp activity (P-gplow); inhibition of efflux transporters was confirmed by the intracellular retention of calcein-AM. The correlation of P-gp activity with HIV-1 viraemia was assessed in naive and memory T cell subsets from 21 HIV-1-infected treatment-naive subjects.

Results

[3H]Raltegravir cellular accumulation ratio decreased in CEM-P-gp cells (P < 0.0001). XR9051 (a P-gp inhibitor) and HIV-1 PIs reversed this phenomenon. Primary CD4+P-gphigh cells accumulated less raltegravir (38.4% ± 9.6%) than P-gplow cells, whereas XR9051 also reversed this effect. In vitro HIV-1 infection of PBMCs and stimulation of CD4+ T cells increased P-gp mRNA and P-gp activity, respectively, while primary CD4+P-gphigh T cells sustained a higher HIV-1 replication than P-gplow cells. A significant correlation between HIV-1 viraemia and P-gp activity was found in different CD4+ T cell subsets, particularly memory CD4+ T cells (r = 0.792, P < 0.0001).

Conclusions

Raltegravir is a substrate of P-gp in CD4+ T cells. Primary CD4+P-gphigh T cells eliminate intracellular raltegravir more readily than P-gplow cells and HIV-1 viraemia correlates with P-gp overall activity. Specific CD4+P-gphigh T cell subsets could facilitate the persistence of viral replication in vivo and ultimately promote the appearance of drug resistance.




Sequential steps of daptomycin resistance in Enterococcus faecium and reversion to hypersusceptibility through IS-mediated inactivation of the liaFSR operon

2016-09-22T00:05:52-07:00

Objectives

To improve understanding of mechanisms of daptomycin resistance and to dissect the genetic basis of reversion to daptomycin hypersusceptibility in Enterococcus faecium.

Methods

Daptomycin-resistant mutants (Mut4, Mut8, Mut16, Mut32, Mut64 and Mut128 with MICs from 4 to 128 mg/L) were obtained in vitro from E. faecium strain Aus0004 (MIC at 2 mg/L). The entire genome sequences of Mut64 and Mut128 were determined as well as those of liaFSR and cls genes for other mutants and corresponding revertants (named Rev4 to Rev128). The study of daptomycin resistance stability was performed without any selective pressure. The expression of liaF, liaS and liaR genes was quantified by quantitative RT–PCR.

Results

By comparative genomic analysis, substitutions Asn13Ser in cls and Gly92Asp in liaS were identified in Mut64 and Mut128. Only the liaS mutation was found in Mut16 and Mut32 while Mut4 and Mut8 were devoid of any mutation. After 15 days, all mutants except Mut4 reverted to daptomycin hypersusceptibility (MICs from 0.12 to 0.25 mg/L). In all revertants (except Rev4 and Rev8), an IS was found in the liaFSR operon with a dramatic decrease of its expression: IS66 in the promoter region of liaF (Rev16 and Rev64), IS30 in liaR (Rev32) and IS982 in liaF (Rev128).

Conclusions

We demonstrated the stepwise and sequential acquisition of mutations in liaS and in cls leading to daptomycin resistance in E. faecium, and the instability of daptomycin resistance as well as the role of liaFSR inactivation in reversion to daptomycin hypersusceptibility.




Transmission of MDR MRSA between primates, their environment and personnel at a United States primate centre

2016-09-22T00:05:52-07:00

Objectives

MDR MRSA isolates cultured from primates, their facility and primate personnel from the Washington National Primate Research Center were characterized to determine whether they were epidemiologically related to each other and if they represented common local human-associated MRSA strains.

Methods

Human and primate nasal and composite environmental samples were collected, enriched and selected on medium supplemented with oxacillin and polymyxin B. Isolates were biochemically verified as Staphylococcus aureus and screened for the mecA gene. Selected isolates were characterized using SCCmec typing, MLST and WGS.

Results

Nasal cultures were performed on 596 primates and 105 (17.6%) were MRSA positive. Two of 79 (2.5%) personnel and two of 56 (3.6%) composite primate environmental facility samples were MRSA positive. Three MRSA isolates from primates, one MRSA from personnel, two environmental MRSA and one primate MSSA were ST188 and were the same strain type by conventional typing methods. ST188 isolates were related to a 2007 ST188 human isolate from Hong Kong. Both MRSA isolates from out-of-state primates had a novel MLST type, ST3268, and an unrelated group. All isolates carried ≥1 other antibiotic resistance gene(s), including tet(38), the only tet gene identified.

Conclusions

ST188 is very rare in North America and has almost exclusively been identified in people from Pan-Asia, while ST3268 is a newly reported MRSA type. The data suggest that the primate MDR MRSA was unlikely to come from primate centre employees. Captive primates are likely to be an unappreciated source of MRSA.




Heterogeneous oxacillin-resistant phenotypes and production of PBP2A by oxacillin-susceptible/mecA-positive MRSA strains from Africa

2016-09-22T00:05:52-07:00

Objectives

Recent surveillance of MRSA colonizing patients and healthcare workers in two African countries (Angola and São Tomé and Príncipe) reported the frequent recovery of oxacillin-susceptible MRSA (OS-MRSA): Staphylococcus aureus strains that gave positive results with the mecA DNA probe, but had low oxacillin MIC values characteristic of susceptible S. aureus. This apparent dissociation of the drug-resistant phenotype from mecA—the primary genetic determinant of resistance—prompted us to perform a more detailed analysis on nine of the African OS-MRSA strains.

Methods

Oxacillin MIC values were determined by Etest and population analysis profiles with and without induction of the stringent stress response by mupirocin. Biochemical profiling using SDS–PAGE followed by western blotting was used for the detection of PBP2A protein produced.

Results

Cultures of the African MRSA strains (ST88-IVa and ST8-V) showed heterogeneous oxacillin resistance in which the majority of cells exhibited low oxacillin MICs (≤0.75 mg/L), but highly resistant subpopulations were also present with oxacillin MIC values up to several hundred mg/L and with frequencies of 10–4 to 10–6. The same strains after induction of the stringent stress response by mupirocin ‘converted’ the heterogeneous phenotypes into a more homogeneous and higher level resistance. After induction by oxacillin and mupirocin, each of the nine African OS-MRSA strains produced PBP2A—the protein product of mecA.

Conclusions

The resistant phenotype of OS-MRSA resembles the phenotypes of historically early MRSA clones. The nature of genetic determinants responsible for the heterogeneous phenotypes of OS-MRSA remains to be determined.




New insights into the regulatory pathways associated with the activation of the stringent response in bacterial resistance to the PBP2-targeted antibiotics, mecillinam and OP0595/RG6080

2016-09-22T00:05:52-07:00

Objectives

The diazabicyclooctane β-lactamase inhibitor OP0595 (RG6080) also acts as an antibiotic, targeting PBP2 in Enterobacteriaceae, but this activity is vulnerable to mutational resistance. We used WGS to investigate the basis of this resistance.

Methods

Twenty OP0595-selected mutants, comprising four derived from each of five different Escherichia coli strains, were sequenced on Illumina HiSeq. Reads from each mutant were mapped to the assembled genome of the corresponding parent. A variant-calling file generated with Samtools was parsed to determine genetic alterations.

Results

Besides OP0595, the mutants consistently showed decreased susceptibility to mecillinam, which likewise targets PBP2, and grew as stable round forms in the presence of subinhibitory concentrations of OP0595. Among the 20 mutants, 18 had alterations in genes encoding tRNA synthase and modification functions liable to induce expression of the RpoS sigma factor through activation of the stringent response or had mutations suppressing inactivators of RpoS or the stringent response signal-degrading enzyme, SpoT. TolB was inactivated in one mutant: this activates RcsBC regulation and was previously associated with mecillinam resistance. The mechanism of resistance remained unidentified in one mutant. Both the RpoS and RcsBC systems regulate genes of cell division, including ftsAQZ that can compensate for loss or inhibition of PBP2, allowing survival of the challenged bacteria as stable round forms, as seen.

Conclusions

WGS identified the global stringent response signal, entailing induction of RpoS, as the main mediator of mutational resistance to OP0595 in E. coli.




Clonality of erythromycin resistance in Francisella tularensis

2016-09-22T00:05:52-07:00

Objectives

We analysed diverse strains of Francisella tularensis subsp. holarctica to assess if its division into biovars I and II is associated with specific mutations previously linked to erythromycin resistance and to determine the distribution of this resistance trait across this subspecies.

Methods

Three-hundred and fourteen F. tularensis subsp. holarctica strains were tested for erythromycin susceptibility and whole-genome sequences for these strains were examined for SNPs in genes previously associated with erythromycin resistance. Each strain was assigned to a global phylogenetic framework using genome-wide canonical SNPs. The contribution of a specific SNP to erythromycin resistance was examined using allelic exchange. The geographical distribution of erythromycin-resistant F. tularensis strains was further investigated by literature search.

Results

There was a perfect correlation between biovar II strains (erythromycin resistance) and the phylogenetic group B.12. Only B.12 strains had an A -> C SNP at position 2059 in the three copies of the rrl gene. Introducing 2059C into an rrl gene of an erythromycin-susceptible F. tularensis strain resulted in resistance. An additional 1144 erythromycin-resistant strains were identified from the scientific literature, all of them from Eurasia.

Conclusions

Erythromycin resistance in F. tularensis is caused by an A2059C rrl gene mutation, which exhibits a strictly clonal inheritance pattern found only in phylogenetic group B.12. This group is an extremely successful clone, representing the most common type of F. tularensis throughout Eurasia.




Characterization of KPC-encoding plasmids from two endemic settings, Greece and Italy

2016-09-22T00:05:52-07:00

Objectives

Global dissemination of KPC-type carbapenemases is mainly associated with the spread of high-risk clones of Klebsiella pneumoniae and of KPC-encoding plasmids. In this study, we explored the population structure of KPC-encoding plasmids from the recent epidemics of KPC-producing K. pneumoniae (KPC-Kp) in Greece and Italy, the two major European endemic settings.

Methods

Thirty-four non-replicate clinical strains of KPC-Kp representative of the early phases (2008–11) of the Greek (n = 22) and Italian (n = 12) epidemics were studied. Isolates were typed by MLST, and blaKPC-carrying plasmids were characterized by S1 profiling, PCR-based replicon typing and RFLP. Transfer experiments by conjugation or transformation were carried out with Escherichia coli recipients. Eleven plasmids, representative of all different restriction profiles, were completely sequenced.

Results

The representative Greek strains belonged to 14 sequence types (STs), with a predominance of ST258. The representative Italian strains belonged to three STs, with a predominance of clonal complex 258 (ST258, ST512). The 34 strains carried plasmids of variable size (78–166 kb), either with blaKPC-2 or blaKPC-3 gene embedded in a Tn4401a transposon. Plasmids from Greek strains were mostly of a single RFLP type (A) and resembled the archetypal pKpQIL KPC-encoding plasmid, while plasmids from Italian strains belonged to a more heterogeneous population, showing five RFLP profiles (A, C–F). Types A and C resembled pKpQIL or deletion derivatives thereof, while types D–F included plasmids with hybrid structures between pKpQIL, pKPN3 and pKPN101-IT.

Conclusions

pKpQIL-like plasmids played a major role in the dissemination of blaKPC in Greece and Italy, but evolved with different dynamics in these endemic settings.




In vitro biological evaluation of novel broad-spectrum isothiazolone inhibitors of bacterial type II topoisomerases

2016-09-22T00:05:52-07:00

Objectives

To evaluate the in vitro biological properties of a novel class of isothiazolone inhibitors of the bacterial type II topoisomerases.

Methods

Inhibition of DNA gyrase and topoisomerase IV activity was assessed using DNA supercoiling and decatenation assays. MIC and MBC were determined according to CLSI guidelines. Antibacterial combinations were assessed using a two-dimensional chequerboard MIC method. Spontaneous frequency of resistance was measured at various multiples of the MIC. Resistant mutants were generated by serial passage at subinhibitory concentrations of antibacterials and genetic mutations were determined through whole genome sequencing. Mammalian cytotoxicity was evaluated using the HepG2 cell line.

Results

Representative isothiazolone compound REDX04957 and its enantiomers (REDX05967 and REDX05990) showed broad-spectrum bactericidal activity against the ESKAPE organisms, with the exception of Enterococcus spp., as well as against a variety of other human bacterial pathogens. Compounds retained activity against quinolone-resistant strains harbouring GyrA S83L and D87G mutations (MIC ≤4 mg/L). Compounds inhibited the supercoiling activity of wild-type DNA gyrase and the decatenation function of topoisomerase IV. Frequency of resistance of REDX04957 at 4x MIC was <9.1 x 10–9. Against a panel of recent MDR isolates, REDX05967 demonstrated activity against Acinetobacter baumannii with MIC50 and MIC90 of 16 and 64 mg/L, respectively. Compounds showed a lack of cytotoxicity against HepG2 cells at 128 mg/L.

Conclusions

Isothiazolone compounds show potent activity against Gram-positive and -negative pathogens with a dual targeting mechanism-of-action and a low potential for resistance development, meriting their continued investigation as broad-spectrum antibacterial agents.




Activation of type II NADH dehydrogenase by quinolinequinones mediates antitubercular cell death

2016-09-22T00:05:52-07:00

Objectives

Quinolinequinones (QQ) have been shown to inhibit the growth of mycobacterial species, but their mode(s) of action and molecular target(s) remain unknown. To facilitate further development of QQ as antimycobacterial drugs, we investigated the molecular mechanism and target of QQ in mycobacteria.

Methods

Cell viability of Mycobacterium tuberculosis and Mycobacterium bovis bacillus Calmette–Guérin was determined in the presence of QQ8c, a representative QQ compound, and isoniazid, a frontline antitubercular drug. The effect of QQ8c on mycobacterial energetics was studied using inverted membrane vesicles. NADH oxidation and formation of reactive oxygen species (ROS) were measured in the presence and absence of KCN. Generation of ROS was measured via oxygen consumption in an oxygen electrode. The effects of QQ8c were compared with the antimycobacterial drug clofazimine in side-by-side experiments.

Results

QQ8c challenge resulted in complete sterilization of cultures with no refractory resistant population observed. QQ8c stimulated NADH oxidation by type II NADH dehydrogenase (NDH-2) and oxygen consumption in inverted membrane vesicles. Large quantities of ROS were produced in the presence of QQ8. Even when oxygen consumption was blocked with KCN, activation of NDH-2 by QQ8c occurred suggesting QQ8c was redox cycling.

Conclusions

QQ8c targets NDH-2 of the mycobacterial respiratory chain leading to activation of NADH oxidation and generating bactericidal levels of ROS in a manner similar to, but more effectively than, the antimycobacterial drug clofazimine. Our results validate respiratory-generated ROS as an avenue for antimycobacterial drug development.




Structural and sequence analysis of class A {beta}-lactamases with respect to avibactam inhibition: impact of {Omega}-loop variations

2016-09-22T00:05:52-07:00

Background

There exists a significant diversity among class A β-lactamases and the proliferation of these enzymes is a significant medical concern due to the ability of some members to efficiently hydrolyse both extended-spectrum cephalosporins and carbapenems. Avibactam is a novel non-β-lactam β-lactamase inhibitor that, in combination with ceftazidime, has recently obtained regulatory approval in the USA. Although avibactam is known to efficiently inhibit key class A enzymes, the diversity of this enzyme family warranted a more complete investigation to understand the breadth of the potential spectrum of inhibition.

Methods

Using the known residues critical for avibactam binding, a thorough structural and sequence-based conservation analysis was performed across >650 class A enzymes. Several variations that had the potential to impact avibactam inhibition were observed and representative enzymes were cloned and expressed isogenically to evaluate the impact of these variations.

Results

The majority of the key residues involved in avibactam binding were well conserved across the different sub-families of class A β-lactamases, although some differences were observed. The differences in the -loop of PER enzymes were found to impact the ability of avibactam to effectively protect β-lactams against hydrolysis. However, substitutions in a key hydrogen-bonding residue (N170) in some of the GES variants were found to not have a significant impact on avibactam inhibition.

Conclusions

Overall, the computational and experimental analyses suggest that the vast majority of class A β-lactamases should be well inhibited by avibactam, although a very small number of outliers exist.




Evaluation of different pretreatment protocols to detect accurately clinical carbapenemase-producing Enterobacteriaceae by MALDI-TOF

2016-09-22T00:05:52-07:00

Objectives

Carbapenemase-resistant bacteria are increasingly spreading worldwide causing public concern due to their ability to elude antimicrobial treatment. Early identification of these bacteria is therefore of high importance. Here, we describe the development of a simple and robust protocol for the detection of carbapenemase activity in clinical isolates of Enterobacteriaceae, suitable for routine and clinical applications.

Methods

The final protocol involves cellular lysis and enzyme extraction from a defined amount of bacterial cells followed by the addition of a benchmark drug (e.g. the carbapenem antibiotic imipenem or ertapenem). Carbapenem inactivation is mediated by enzymatic hydrolysis (cleavage) of the β-lactam common structural motif, which can be detected using MALDI-TOF MS.

Results

A total of 260 strains were studied (208 carbapenemase producers and 52 non-carbapenemase producers) resulting in 100% sensitivity and 100% specificity for the KPC, NDM and OXA-48-like PCR-confirmed positive isolates using imipenem as benchmark. Differences between the benchmark (indicator) antibiotics imipenem and ertapenem, buffer constituents and sample preparation methods have been investigated. Carbapenemase activity was further characterized by performing specific inhibitor experiments. Intraday and interday reproducibility (coefficient of variation) of the observed hydrolysis results were 15% and 30%, respectively. A comparative study of our extraction method and a recently published method using whole bacterial cells is presented and differences are discussed.

Conclusions

Using this method, an existing carbapenemase activity can be directly read from the mass spectrum as a ratio of hydrolysed product and substrate, setting an important step towards routine application in clinical laboratories.




Activity of a long-acting echinocandin, CD101, determined using CLSI and EUCAST reference methods, against Candida and Aspergillus spp., including echinocandin- and azole-resistant isolates

2016-09-22T00:05:52-07:00

Objectives

The objective of this study was to evaluate the in vitro activity of CD101, a novel echinocandin with a long serum elimination half-life, and comparator (anidulafungin and caspofungin) antifungal agents against a collection of Candida and Aspergillus spp. isolates.

Methods

CD101 and comparator agents were tested against 106 Candida spp. and 67 Aspergillus spp. isolates, including 27 isolates of Candida harbouring fks hotspot mutations and 12 itraconazole non-WT Aspergillus, using CLSI and EUCAST reference susceptibility broth microdilution (BMD) methods.

Results

Against WT and fks mutant Candida albicans, Candida glabrata and Candida tropicalis, the activity of CD101 [MIC90 = 0.06, 0.12 and 0.03 mg/L, respectively (CLSI method values)] was comparable to that of anidulafungin (MIC90 = 0.03, 0.12 and 0.03 mg/L, respectively) and caspofungin (MIC90 = 0.12, 0.25 and 0.12 mg/L, respectively). WT Candida krusei isolates were very susceptible to CD101 (MIC = 0.06 mg/L). CD101 activity (MIC50/90 = 1/2 mg/L) was comparable to that of anidulafungin (MIC50/90 = 2/2 mg/L) against Candida parapsilosis. CD101 (MIC mode = 0.06 mg/L for C. glabrata) was 2- to 4-fold more active against fks hotspot mutants than caspofungin (MIC mode = 0.5 mg/L). CD101 was active against Aspergillus fumigatus, Aspergillus terreus, Aspergillus niger and Aspergillus flavus (MEC90 range = ≤0.008–0.03 mg/L). The essential agreement between CLSI and EUCAST methods for CD101 was 92.0%–100.0% among Candida spp. and 95.0%–100.0% among Aspergillus spp.

Conclusions

The activity of CD101 is comparable to that of other members of the echinocandin class for the prevention and treatment of serious fungal infections. Similar results for CD101 activity versus Candida and Aspergillus spp. may be obtained with either CLSI or EUCAST BMD methods.




High susceptibility of MDR and XDR Gram-negative pathogens to biphenyl-diacetylene-based difluoromethyl-allo-threonyl-hydroxamate LpxC inhibitors

2016-09-22T00:05:52-07:00

Objectives

Inhibitors of uridine diphosphate-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase (LpxC, which catalyses the first, irreversible step in lipid A biosynthesis) are a promising new class of antibiotics against Gram-negative bacteria. The objectives of the present study were to: (i) compare the antibiotic activities of three LpxC inhibitors (LPC-058, LPC-011 and LPC-087) and the reference inhibitor CHIR-090 against Gram-negative bacilli (including MDR and XDR isolates); and (ii) investigate the effect of combining these inhibitors with conventional antibiotics.

Methods

MICs were determined for 369 clinical isolates (234 Enterobacteriaceae and 135 non-fermentative Gram-negative bacilli). Time–kill assays with LPC-058 were performed on four MDR/XDR strains, including Escherichia coli producing CTX-M-15 ESBL and Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii producing KPC-2, VIM-1 and OXA-23 carbapenemases, respectively.

Results

LPC-058 was the most potent antibiotic and displayed the broadest spectrum of antimicrobial activity, with MIC90 values for Enterobacteriaceae, P. aeruginosa, Burkholderia cepacia and A. baumannii of 0.12, 0.5, 1 and 1 mg/L, respectively. LPC-058 was bactericidal at 1x or 2x MIC against CTX-M-15, KPC-2 and VIM-1 carbapenemase-producing strains and bacteriostatic at ≤4x MIC against OXA-23 carbapenemase-producing A. baumannii. Combinations of LPC-058 with β-lactams, amikacin and ciprofloxacin were synergistic against these strains, albeit in a species-dependent manner. LPC-058's high efficacy was attributed to the presence of the difluoromethyl-allo-threonyl head group and a linear biphenyl-diacetylene tail group.

Conclusions

These in vitro data highlight the therapeutic potential of the new LpxC inhibitor LPC-058 against MDR/XDR strains and set the stage for subsequent in vivo studies.




Pharmacodynamics and differential activity of nitrofurantoin against ESBL-positive pathogens involved in urinary tract infections

2016-09-22T00:05:52-07:00

Background

Although nitrofurantoin has been used for >60 years for the treatment of uncomplicated urinary tract infections, its pharmacodynamic properties are not fully explored. Use is increasing because of increasing resistance to other antimicrobials due to ESBLs.

Methods

We tested nine ESBL+ and two ESBL– strains in time–kill assays. Bactericidal activity and regrowth were assessed for all species and concentrations. Early-phase pharmacodynamics was analysed with a sigmoidal Emax model and the maximal killing rate, slope and EC50/MIC ratio were determined for each species.

Results

A bactericidal effect was found at ≥2x MIC for Enterobacter cloacae after 4–8 h, for Klebsiella pneumoniae after 8–10 h and for Escherichia coli after 12–16 h. Overall, no killing was observed at low sub-MIC concentrations, whereas regrowth was found at 0.5–1x MIC after a short decline in cfu. The lowest maximal killing rates were observed for E. coli (0.21 ± 0.05 h–1), followed by K. pneumoniae (0.37 ± 0.09 h–1) and E. cloacae (0.87 ± 0.01 h–1). Surprisingly, the Hill slopes for these three species were significantly different (10.45 ± 9.37, 2.68 ± 0.64 and 1.01 ± 0.06, respectively), indicating a strong concentration-dependent early-phase antibacterial activity against E. cloacae. EC50/MIC ratios were significantly lower for E. coli (0.24 ± 0.08 mg/L) and K. pneumoniae (0.27 ± 0.03 mg/L) as compared with E. cloacae (0.77 ± 0.18 mg/L).

Conclusions

Nitrofurantoin was bactericidal against all species, demonstrating an unusual differential pattern of activity with concentration-dependent-type killing behaviour against E. cloacae and time-dependent killing behaviour against E. coli, which may have significant consequences on species-dependent dosing regimens. The results also demonstrate that the pharmacodynamic properties of some drugs cannot be generalized within a family, here the Enterobacteriaceae.




Comparative efficacy of telavancin and daptomycin in experimental endocarditis due to multi-clonotype MRSA strains

2016-09-22T00:05:52-07:00

Background

MRSA strains of clonal complexes (CCs) 5, 8, 30 and 45 are leading causes of complicated endovascular infections associated with suboptimal clinical outcomes. Telavancin is a novel anti-MRSA agent that both inhibits bacterial cell wall synthesis and disrupts membranes by depolarization.

Methods

In this study, we compared the in vitro susceptibility and in vivo efficacy of telavancin versus daptomycin in an experimental rabbit infective endocarditis (IE) model caused by four MRSA strains representing each of the above CC types.

Results

All study strains were susceptible to telavancin (MICs of ≤0.12 mg/L) and daptomycin (MICs of ≤0.5 mg/L). In vitro time–kill analyses revealed that supra-MIC levels of telavancin were effective at preventing regrowth at 24 h of incubation. In the IE animal model for all CC types, treatment with telavancin produced significantly greater reductions in MRSA counts as compared with daptomycin-treated animals in all target tissues. Moreover, telavancin-treated animals had a significantly higher percentage of sterile tissue cultures versus daptomycin-treated animals (e.g. 78%–100% versus 0% sterile vegetations and 100% versus 0%–11% sterile kidneys and spleen, in the telavancin- and daptomycin-treated animals, respectively).

Conclusions

These results suggest that telavancin exhibits significantly greater efficacies versus daptomycin in treating experimental IE caused by MRSA clinical isolates across four common CC types.




Efficacy of anidulafungin in the treatment of experimental Candida parapsilosis catheter infection using an antifungal-lock technique

2016-09-22T00:05:52-07:00

Objectives

The effectiveness of anidulafungin versus liposomal amphotericin B (LAmB) for treating experimental Candida parapsilosis catheter-related infection by an antifungal-lock technique was assessed.

Methods

Two clinical strains of C. parapsilosis (CP12 and CP54) were studied. In vitro studies were used to determine the biofilm MICs (MBIC50 and MBIC90) by XTT reduction assay and LIVE/DEAD biofilm viability for anidulafungin and LAmB on 96-well microtitre polystyrene plates and silicone discs. An intravenous catheter was implanted in New Zealand white rabbits. Infection was induced by locking the catheter for 48 h with the inoculum. The 48 h antifungal-lock treatment groups included control, 3.3 mg/mL anidulafungin and 5.5 mg/mL LAmB.

Results

Anidulafungin showed better in vitro activity than LAmB against C. parapsilosis growing in biofilm on silicone discs. MBIC90 of LAmB: CP12, >1024 mg/L; CP54, >1024 mg/L. MBIC90 of anidulafungin: CP12, 1 mg/L; CP54, 1 mg/L (P ≤ 0.05). Moreover, only anidulafungin (1 mg/L) showed >90% non-viable cells in the LIVE/DEAD biofilm viability assay on silicone discs. No differences were observed between the in vitro susceptibility of anidulafungin or LAmB when 96-well plates were used. Anidulafungin achieved significant reductions relative to LAmB in log10 cfu recovered from the catheter tips for both strains (P ≤ 0.05). Only anidulafungin achieved negative catheter tip cultures (CP12 63%, CP54 73%, P ≤ 0.05).

Conclusions

Silicone discs may be a more reliable substrate for the study of in vitro biofilm susceptibility of C. parapsilosis. Anidulafungin-lock therapy showed the highest activity for experimental catheter-related infection with C. parapsilosis.




Integrated pharmacokinetic-pharmacodynamic modelling to evaluate antimicrobial prophylaxis in abdominal surgery

2016-09-22T00:05:52-07:00

Objectives

To use Monte Carlo simulation with an integrated pharmacokinetic–pharmacodynamic (PK-PD) model to evaluate guideline-recommended antimicrobial prophylaxis (AP) regimens with anaerobic coverage in abdominal surgery.

Methods

AP regimens were tested in simulated subjects undergoing elective abdominal surgery using relevant PK models and pathogen distributions in surgical site infections (SSIs). Predicted cumulative target attainment was the percentage of simulated subjects with free (unbound) antimicrobial plasma concentrations above the MICs for potential SSI pathogens.

Results

Cefazolin plus metronidazole covered SSI aerobes in 70% and the Bacteroides fragilis group in 99% of subjects, whereas cefoxitin only covered aerobes and anaerobes in 63% and 27% of cases, respectively. The broad-spectrum ceftriaxone plus metronidazole covered aerobes in 82% and anaerobes in 99% of simulations, while ertapenem covered aerobes in 88% and anaerobes in 90% of cases. Clindamycin covered the B. fragilis group in only 11% of cases. For cefazolin, 2 g doses maintained target attainment in simulated subjects from 80 to 120 kg, whereas 1 g doses were associated with lower target attainment against potential Gram-negative pathogens even in those <80 kg. For gentamicin, 3 mg/kg doses were comparable to the suggested 5 mg/kg, but superior to the traditional 1.5 mg/kg.

Conclusions

This study demonstrates the use of PK-PD to inform decisions regarding AP in abdominal surgery. In this case, the findings support avoiding cefoxitin, avoiding clindamycin for anaerobic coverage, selecting 2 g doses of cefazolin even in patients <80 kg and using 3 mg/kg doses of gentamicin.




Non-linear absorption pharmacokinetics of amoxicillin: consequences for dosing regimens and clinical breakpoints

2016-09-22T00:05:52-07:00

Objectives

To describe the population pharmacokinetics of oral amoxicillin and to compare the PTA of current dosing regimens.

Methods

Two groups, each with 14 healthy male volunteers, received oral amoxicillin/clavulanic acid tablets on two separate days 1 week apart. One group received 875/125 mg twice daily and 500/125 mg three times daily and the other group 500/125 mg twice daily and 250/125 mg three times daily. A total of 1428 amoxicillin blood samples were collected before and after administration. We analysed the concentration–time profiles using a non-compartmental pharmacokinetic method (PKSolver) and a population pharmacokinetic method (NONMEM). The PTA was computed using Monte Carlo simulations for several dosing regimens.

Results

AUC0–24 and Cmax increased non-linearly with dose. The final model included the following components: Savic's transit compartment model, Michaelis–Menten absorption, two distribution compartments and first-order elimination. The mean central volume of distribution was 27.7 L and mean clearance was 21.3 L/h. We included variability for the central volume of distribution (34.4%), clearance (25.8%), transit compartment model parameters and Michaelis–Menten absorption parameters. For 40% fT>MIC and >97.5% PTA, the breakpoints were 0.125 mg/L (500 mg twice daily), 0.25 mg/L (250 mg three times daily and 875 mg twice daily), 0.5 mg/L (500 mg three times daily) and 1 mg/L (750, 875 or 1000 mg three times daily and 500 mg four times daily).

Conclusions

The amoxicillin absorption rate appears to be saturable. The PTAs of high-dose as well as twice-daily regimens are less favourable than regimens with lower doses and higher frequency.




Accumulation of HIV-1 drug resistance after continued virological failure on first-line ART in adults and children in sub-Saharan Africa

2016-09-22T00:05:52-07:00

Objectives

Limited availability of viral load (VL) monitoring in HIV treatment programmes in sub-Saharan Africa can delay switching to second-line ART, leading to the accumulation of drug resistance mutations (DRMs). The objective of this study was to evaluate the accumulation of resistance to reverse transcriptase inhibitors after continued virological failure on first-line ART, among adults and children in sub-Saharan Africa.

Methods

HIV-1-positive adults and children on an NNRTI-based first-line ART were included. Retrospective VL and, if VL ≥1000 copies/mL, pol genotypic testing was performed. Among participants with continued virological failure (≥2 VL ≥1000 copies/mL), drug resistance was evaluated.

Results

At first virological failure, DRM(s) were detected in 87% of participants: K103N (38.7%), G190A (21.8%), Y181C (20.2%), V106M (8.4%), K101E (8.4%), any E138 (7.6%) and V108I (7.6%) associated with NNRTIs, and M184V (69.7%), any thymidine analogue mutation (9.2%), K65R (5.9%) and K70R (5.0%) associated with NRTIs. New DRMs accumulated with an average rate of 1.45 (SD 2.07) DRM per year; 0.62 (SD 1.11) NNRTI DRMs and 0.84 (SD 1.38) NRTI DRMs per year, respectively. The predicted susceptibility declined significantly after continued virological failure for all reverse transcriptase inhibitors (all P < 0.001). Acquired drug resistance patterns were similar in adults and children.

Conclusions

Patterns of drug resistance after virological failure on first-line ART are similar in adults and children in sub-Saharan Africa. Improved VL monitoring to prevent accumulation of mutations, and new drug classes to construct fully active regimens, are required.




An update to the HIV-TRePS system: the development and evaluation of new global and local computational models to predict HIV treatment outcomes, with or without a genotype

2016-09-22T00:05:52-07:00

Objectives

Optimizing antiretroviral drug combination on an individual basis in resource-limited settings is challenging because of the limited availability of drugs and genotypic resistance testing. Here, we describe our latest computational models to predict treatment responses, with or without a genotype, and compare the potential utility of global and local models as a treatment tool for South Africa.

Methods

Global random forest models were trained to predict the probability of virological response to therapy following virological failure using 29 574 treatment change episodes (TCEs) without a genotype, 3179 of which were from South Africa and were used to develop local models. In addition, 15 130 TCEs including genotypes were used to develop another set of models. The ‘no-genotype’ models were tested with an independent global test set (n = 1700) plus a subset from South Africa (n = 222). The genotype models were tested with 750 independent cases.

Results

The global no-genotype models achieved area under the receiver-operating characteristic curve (AUC) values of 0.82 and 0.79 with the global and South African tests sets, respectively, and the South African models achieved AUCs of 0.70 and 0.79. The genotype models achieved an AUC of 0.84. The global no-genotype models identified more alternative, locally available regimens that were predicted to be effective for cases that failed their new regimen in the South African clinics than the local models. Both sets of models were significantly more accurate predictors of outcomes than genotyping with rules-based interpretation.

Conclusions

These latest global models predict treatment responses accurately even without a genotype, out-performed the local South African models and have the potential to help optimize therapy, particularly in resource-limited settings.




Short-term risk of liver and renal injury in hospitalized patients using micafungin: a multicentre cohort study

2016-09-22T00:05:52-07:00

Background

Although echinocandins are generally well tolerated, there is little information on the frequency with which renal and hepatic adverse effects occur during use of micafungin or other parenteral antifungal (PAF) agents in clinical practice.

Methods

MYCOS is a multicentre cohort study of adult and paediatric patients who received micafungin or other PAFs between 2005 and 2012 at seven tertiary care hospitals from six centres in the USA. PAF cohort controls were selected through propensity score (PS) matching to micafungin recipients using clinical characteristics, other treatments, procedures and hospital service where PAF treatment was initiated. Analysis was restricted to patients without chronic liver and kidney conditions at the time of cohort entry. Treatment-emergent hepatic and renal injury was documented by changes in liver enzymes or estimated glomerular filtration rate through 30 days following completion of PAF treatment. Comparisons were quantified using the HR from a proportional hazards analysis.

Results

There were 2970 micafungin recipients PS matched to 6726 recipients of comparator PAFs. Balance was achieved in all baseline covariates between treatment groups. There were similar rates of hepatic injury (micafungin, 13 events per 100 patients and other PAF, 12 per 100; HR = 0.99; 95% CI 0.86–1.14) and lower rates of renal injury (micafungin, 63 events per 100 patients and other PAF, 65 per 100; HR = 0.93; 95% CI 0.87–0.99) for micafungin recipients versus PAF comparators.

Conclusion

For a wide spectrum of underlying conditions, we observed no increase in liver injury by micafungin and possibly a reduced risk of renal dysfunction in comparison with other PAF medications.




Rise and fall of KPC-producing Klebsiella pneumoniae in New York City

2016-09-22T00:05:52-07:00

Objectives

The study objective was to examine the epidemiological trends of KPC-producing Klebsiella pneumoniae in New York City medical centres.

Patients and methods

Single patient isolates of K. pneumoniae were collected from nine medical centres in New York City during a 3 month period from 2013 to 2014. Isolates were tested for the presence of blaKPC. Results were compared with similar surveillance studies conducted in 2006 and 2009. Infection control data, including utilization of medical devices, were analysed at a subset of hospitals.

Results

There was a progressive decline in the percentage of K. pneumoniae harbouring blaKPC from 2006 to 2013–14. For the nine hospitals that participated in all three surveillance studies, the percentages of isolates with blaKPC fell from 36% in 2006 to 25% in 2009 to 13% in 2013–14. Seven of the nine hospitals had marked declines in isolates with blaKPC, while two hospitals continued to struggle with this pathogen. These two hospitals were smaller and had longer lengths of patient stay. Device utilization rates were obtained from two hospitals that successfully controlled the spread of KPC-producing K. pneumoniae; both had ~20%–25% reduction in the usage of urinary catheters. Changes in antibiotic usage at one hospital could not explain the decline in these pathogens.

Conclusions

Over the past decade there has been a steady decline in KPC-producing K. pneumoniae in most New York City hospitals. The reason for the decline is probably multifactorial, involving a reduction in device (catheter) utilization and possibly an improvement in infection control practices.




ESBL-producing Escherichia coli ST131 versus non-ST131: evolution and risk factors of carriage among French children in the community between 2010 and 2015

2016-09-22T00:05:52-07:00

Objectives

The objective of this study was to evaluate the evolution and risk factors of ESBL-producing Enterobacteriaceae (ESBL-E) carriage in children in the community for a long period distinguishing ST131 and non-ST131 Escherichia coli.

Patients and methods

In this prospective study, rectal samples were obtained from children aged 6–24 months by community paediatricians between 2010 and 2015. Demographic characteristics and risk factors for ESBL-E carriage were collected. Distribution of β-lactamase genes, phylogenetic groups, ST131 and virulence factors of resistant E. coli was determined.

Results

We enrolled 1886 children; 144 (7.6%) harboured ESBL-E, and this rate increased from 4.8% to 10.2% between 2010 and 2015. Risk factors for ESBL-E carriage were being cared for at home [adjusted OR (aOR) = 1.8, 95% CI = 1.1–2.9], recent antibiotic use (aOR = 1.5, 95% CI = 1.0–2.1) and travel history (aOR = 1.7, 95% CI = 1.1–2.6). Among patients carrying ESBL, E. coli (98%) and CTX-M type (90%) predominated and PapGII adhesin, characteristic of pyelonephritogenic E. coli strains, was rare (7%). In 2015, E. coli isolates frequently belonged to the phylogenetic group B2 (48%), and 37% were ST131 compared with 5% in 2010. Compared with non-ESBL-producing strains, ST131 carriage was associated with hospitalization in the last 6 months (aOR = 3.5, 95% CI = 1.4–8.8).

Conclusions

Between 2010 and 2015, the carriage of ESBL-E in community children doubled because of the massive expansion of the E. coli ST131 clonal group. The risk for carrying ST131 was associated with previous hospitalization, but not, contrary to the counterpart, antibiotic treatment, daycare attendance or travel history.




Colonization with third-generation cephalosporin-resistant Enterobacteriaceae on hospital admission: prevalence and risk factors

2016-09-22T00:05:53-07:00

Objectives

The objectives of this study were to prospectively assess the rectal carriage rate of third-generation cephalosporin-resistant Enterobacteriaceae (3GCREB) in non-ICU patients on hospital admission and to investigate resistance mechanisms and risk factors for carriage.

Methods

Adult patients were screened for 3GCREB carriage at six German tertiary care hospitals in 2014 using rectal swabs or stool samples. 3GCREB isolates were characterized by phenotypic and molecular methods. Each patient answered a questionnaire about potential risk factors for colonization with MDR organisms (MDROs). Univariable and multivariable risk factor analyses were performed to identify factors associated with 3GCREB carriage.

Results

Of 4376 patients, 416 (9.5%) were 3GCREB carriers. Escherichia coli was the predominant species (79.1%). ESBLs of the CTX-M-1 group (67.3%) and the CTX-M-9 group (16.8%) were the most frequent β-lactamases. Five patients (0.11%) were colonized with carbapenemase-producing Enterobacteriaceae. The following risk factors were significantly associated with 3GCREB colonization in the multivariable analysis (P < 0.05): centre; previous MDRO colonization (OR = 2.12); antibiotic use within the previous 6 months (OR = 2.09); travel outside Europe (OR = 2.24); stay in a long-term care facility (OR = 1.33); and treatment of gastroesophageal reflux disease (GERD) (OR = 1.22).

Conclusions

To our knowledge, this is the largest admission prevalence study of 3GCREB in Europe. The observed prevalence of 9.5% 3GCREB carriage was higher than previously reported and differed significantly among centres. In addition to previously identified risk factors, the treatment of GERD proved to be an independent risk factor for 3GCREB colonization.




Surotomycin versus vancomycin for Clostridium difficile infection: Phase 2, randomized, controlled, double-blind, non-inferiority, multicentre trial

2016-09-22T00:05:53-07:00

Objectives

Clostridium difficile infection (CDI) is a major public health concern. Treatment with commonly prescribed antibiotics is associated with high rates of recurrence after initial cure. Here, we present the efficacy and safety of surotomycin, an orally administered, minimally absorbed, selective bactericidal cyclic lipopeptide, compared with vancomycin, in patients with CDI.

Methods

In this Phase 2, randomized, controlled, double-blind, non-inferiority, multicentre trial, participants received surotomycin 125 mg twice daily, surotomycin 250 mg twice daily or vancomycin 125 mg four times daily for 10 days. The primary efficacy outcome was clinical response at end of treatment. The registration number of the study on clinicaltrials.gov is NCT01085591.

Results

Clinical cure rates were similar among treatment groups (92.4% for surotomycin 125 mg twice daily, 86.6% for surotomycin 250 mg twice daily and 89.4% for vancomycin). Recurrence rates were 27.9% for surotomycin 125 mg twice daily, 17.2% for surotomycin 250 mg twice daily and 35.6% for vancomycin. The lower recurrence rate with surotomycin 250 mg twice daily versus vancomycin was statistically significant (P = 0.035). Recurrence rates were statistically similar between the surotomycin dose groups (P = 0.193). Rates of sustained clinical response at end of study were 66.7% for surotomycin 125 mg twice daily, 70.1% for surotomycin 250 mg twice daily and 56.1% for vancomycin. Incidence of adverse events was similar among treatment arms.

Conclusions

Recurrence rates of CDI were lower with surotomycin with higher sustained clinical response rates compared with vancomycin, both of which may offer potential clinical benefits.




Development and validation of the knowledge and attitudes regarding antibiotics and resistance (KAAR-11) questionnaire for primary care physicians

2016-09-22T00:05:53-07:00

Objectives

The aim of this study was to develop a novel, self-administered questionnaire to identify primary-care physicians' knowledge and attitudes regarding antibiotics and resistance (KAAR).

Methods

The study population comprised primary care physicians. The study was conducted in five phases. Phase I consisted of a systematic review and qualitative focus-group study (n = 33 physicians), in which items were formulated so as to be measured on a continuous, visual analogue scale (VAS); in Phase II, content validation and face validity were evaluated by a panel of experts, which reformulated, added and deleted items; Phase III consisted of a pilot study on a population possessing similar characteristics (n = 15); in Phase IV, we analysed reliability by means of a test–retest study (n = 91) and calculated the intraclass correlation coefficients (ICCs); and in Phase V, we assessed construct validity by applying the known-groups technique, measuring the differences between contrasting groups of physicians formed according to antibiotic prescription quality indicators (group 1, n = 156 versus group 2, n = 191).

Results

Following Phases I and II, the questionnaire contained 16 knowledge and attitude items. Participants in the pilot study (Phase III) reported no difficulty. The test–retest study (Phase IV) showed that 11 of the 16 initial knowledge and attitude items yielded an ICC > 0.5, while analysis of known-groups validity (Phase V) showed that 13 of the 16 initial items which assessed knowledge and attitudes discriminated between physicians with good and bad indicators of antibiotics prescription.

Conclusion

The final 11 item KAAR questionnaire appears to be valid, reliable and responsive.




Assessment of appropriate antimicrobial prescribing: do experts agree?

2016-09-22T00:05:53-07:00

Objectives

Little is known about the validity and reliability of expert assessments of the quality of antimicrobial prescribing, despite their importance in antimicrobial stewardship. We investigated how infectious disease doctors' assessments compared with a reference standard (modal expert opinion) and with the assessments of their colleagues.

Methods

Twenty-four doctors specialized in infectious diseases or clinical microbiology (16 specialists and 8 residents) from five hospitals were asked to assess the appropriateness of antimicrobial agents prescribed for a broad spectrum of indications in 56 paper cases. They were instructed how to handle guideline applicability and deviations. We created a reference standard of antimicrobial appropriateness using the modal assessment of 16 specialists. We calculated criterion validity and interrater and intrarater overall and specific agreement with an index expert (senior infectious disease physician) and analysed the influence of doctor characteristics on validity.

Results

Specialists agreed with the reference standard in 80% of cases (range 75%–86%), with a sensitivity and specificity of 75% and 84%, respectively. This did not differ by clinical specialty, hospital or years of experience, and residents had similar results. Specialists agreed with the index expert in 76% of cases and the index expert agreed with his previous assessments in 71% of cases.

Conclusions

Doctors specialized in infectious diseases and clinical microbiology assess the appropriateness of antimicrobials prescribed for a broad spectrum of indications with acceptable agreement and validity, regardless of their experience or hospital of employment. However, there is room for improvement, which merits attention in multidisciplinary discussions and education.