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Preview: Journal of Antimicrobial Chemotherapy - current issue

Journal of Antimicrobial Chemotherapy Current Issue

Published: Tue, 14 Mar 2017 00:00:00 GMT

Last Build Date: Thu, 27 Apr 2017 13:51:15 GMT


Polymyxin-resistant, carbapenem-resistant Acinetobacter baumannii is eradicated by a triple combination of agents that lack individual activity


Objectives: The emergence of polymyxin resistance threatens to leave clinicians with few options for combatting drug-resistant Acinetobacter baumannii. The objectives of the current investigation were to define the in vitro emergence of polymyxin resistance and identify a combination regimen capable of eradicating A. baumannii with no apparent drug susceptibilities.Methods: Two clonally related, paired, A. baumannii isolates collected from a critically ill patient who developed colistin resistance while receiving colistin methanesulfonate in a clinical population pharmacokinetic study were evaluated: an A. baumannii isolate collected before (03-149.1, polymyxin-susceptible, MIC 0.5 mg/L) and an isolate collected after (03-149.2, polymyxin-resistant, MIC 32 mg/L, carbapenem-resistant, ampicillin/sulbactam-resistant). Using the patient’s unique pharmacokinetics, the patient’s actual regimen received in the clinic was recreated in a hollow-fibre infection model (HFIM) to track the emergence of polymyxin resistance against 03-149.1. A subsequent HFIM challenged the pan-resistant 03-149.2 isolate against polymyxin B, meropenem and ampicillin/sulbactam alone and in two-drug and three-drug combinations.Results: Despite achieving colistin steady-state targets of an AUC0–24 >60 mg·h/L and Cavg of >2.5 mg/L, colistin population analysis profiles confirmed the clinical development of polymyxin resistance. During the simulation of the patient’s colistin regimen in the HFIM, no killing was achieved in the HFIM and amplification of polymyxin resistance was observed by 96 h. Against the polymyxin-resistant isolate, the triple combination of polymyxin B, meropenem and ampicillin/sulbactam eradicated the A. baumannii by 96 h in the HFIM, whereas monotherapies and double combinations resulted in regrowth.Conclusions: To combat polymyxin-resistant A. baumannii, the triple combination of polymyxin B, meropenem and ampicillin/sulbactam holds great promise.

Obtaining antibiotics online from within the UK: a cross-sectional study


Background: Improved antibiotic stewardship (AS) and reduced prescribing in primary care, with a parallel increase in personal internet use, could lead citizens to obtain antibiotics from alternative sources online.Objectives: A cross-sectional analysis was performed to: (i) determine the quality and legality of online pharmacies selling antibiotics to the UK public; (ii) describe processes for obtaining antibiotics online from within the UK; and (iii) identify resulting AS and patient safety issues.Methods: Searches were conducted for ‘buy antibiotics online’ using Google and Yahoo. For each search engine, data from the first 10 web sites with unique URL addresses were reviewed. Analysis was conducted on evidence of appropriate pharmacy registration, prescription requirement, whether antibiotic choice was ‘prescriber-driven’ or ‘consumer-driven’, and whether specific information was required (allergies, comorbidities, pregnancy) or given (adverse effects) prior to purchase.Results: Twenty unique URL addresses were analysed in detail. Online pharmacies evidencing their location in the UK (n = 5; 25%) required a prescription before antibiotic purchase, and were appropriately registered. Online pharmacies unclear about the location they were operating from (n = 10; 50%) had variable prescription requirements, and no evidence of appropriate registration. Nine (45%) online pharmacies did not require a prescription prior to purchase. For 16 (80%) online pharmacies, decisions were initially consumer-driven for antibiotic choice, dose and quantity.Conclusions: Wide variation exists among online pharmacies in relation to antibiotic practices, highlighting considerable patient safety and AS issues. Improved education, legislation, regulation and new best practice stewardship guidelines are urgently needed for online antibiotic suppliers.

Antimicrobial strategy for severe community-acquired legionnaires’ disease: a multicentre retrospective observational study


Background: Legionnaires’ disease (LD) is an important cause of community-acquired pneumonia with high mortality rates in the most severe cases.Objectives: To evaluate the effect of antimicrobial strategy on ICU mortality.Methods: Retrospective, observational study including patients admitted to 10 ICUs for severe community-acquired LD over a 10 year period (2005–15) and receiving an active therapy within 48 h of admission. Patients were stratified according to the antibiotic strategy administered: (i) fluoroquinolone-based versus non-fluoroquinolone-based therapy; and (ii) monotherapy versus combination therapy. The primary endpoint was in-ICU mortality. A multivariable Cox model and propensity score analyses were used.Results: Two hundred and eleven patients with severe LD were included. A fluoroquinolone-based and a combination therapy were administered to 159 (75%) and 123 (58%) patients, respectively. One hundred and forty-six patients (69%) developed acute respiratory distress syndrome and 54 (26%) died in the ICU. In-ICU mortality was lower in the fluoroquinolone-based than in the non-fluoroquinolone-based group (21% versus 39%, P =0.01), and in the combination therapy than in the monotherapy group (20% versus 34%, P =0.02). In multivariable analysis, a fluoroquinolone-based therapy, but not a combination therapy, was associated with a reduced risk of mortality [HR = 0.41, 95% CI 0.19–0.89; P =0.02].Conclusions: Patients with severe LD receiving a fluoroquinolone-based antimicrobial regimen in the early course of management had a lower in-ICU mortality, which persisted after adjusting for significant covariates.

OXA-48-like carbapenemases in the UK: an analysis of isolates and cases from 2007 to 2014


Objectives: OXA-48-like carbapenemases have spread worldwide since 2001. We analysed patient and microbiological data for UK isolates with these enzymes as confirmed by the national reference laboratory from November 2007 to December 2014.Methods: MICs were determined using BSAC agar dilution. Isolates with reduced susceptibility or resistance to at least one carbapenem and high-level resistance to both piperacillin/tazobactam (MICs ≥64 mg/L) and temocillin (MICs ≥128 mg/L) were screened by PCR for blaOXA-48-like genes. The genomes of about half of the isolates were sequenced, with MLST types, resistance genes and plasmid replicon types inferred. Patient data provided by sending laboratories were reviewed.Results: Isolates (n =741) with OXA-48-like carbapenemases were submitted from 111 UK laboratories, representing 536 patients. Almost all (99%; 736 of 741) were Enterobacteriaceae, predominantly Klebsiella pneumoniae (55%; 408), and most (80%; 595) were from inpatients. WGS of 351 non-duplicate isolates identified blaOXA-48 as the most common variant, found in two-thirds (235 of 351) of isolates, followed by blaOXA-181 (68), blaOXA-232 (32), blaOXA-244 (10), blaOXA-484 (5) and blaOXA-245 (1). Among K. pneumoniae (163 of 351), Escherichia coli (114 of 351) and Enterobacter cloacae (42 of 351), 119 STs were identified. Mapping analyses revealed that 63% (222 of 351) of isolates harboured plasmids that shared >99% identity to one of four known plasmids [pOXA-48a (44%; 154 of 351), pOXA-232 (10%; 34 of 351), pOXA181 (9%; 30 of 351) and pKP3-A (1%; 4 of 351)]; the remaining 37% of isolates harboured blaOXA-48-like in unknown environments.Conclusions: OXA-48-like carbapenemases are an increasing problem in the UK. This study highlights both the role of successful plasmids and the polyclonal nature of their dissemination.

Risk factors and impact of Clostridium difficile recurrence on haematology patients


Objectives: The incidence of Clostridium difficile infection (CDI) in adults with malignancy is 7%–14% compared with 1%–2% in the general hospitalized population. Despite the increased incidence of CDI in this population, a major concern is the propensity of CDI to recur, leading to delays in therapy impacting outcomes. We conducted a retrospective case–control study to identify risk factors for recurrent CDI (rCDI) and to determine the impact of rCDI on adult patients with a haematological malignancy.Methods: Adult haematology patients with CDI from June 2010 to December 2014 were divided into two groups: rCDI and non-rCDI. Multivariable models using logistic regression were constructed to identify risk factors for rCDI.Results: A total of 100 patients in our study yielded a 41% recurrence rate. CDI impacted chemotherapy significantly more in the rCDI group (53.7% versus 11.9%, P <0.001), primarily due to interruptions in established treatment plans (46.3% versus 10.3%, P <0.001). Risk factors for rCDI identified at index included salvage lymphoma chemotherapy (OR 9.64, 95% CI 1.02–91.15, P = 0.048) and severe CDI (OR 4.82, 95% CI 1.31–17.66, P = 0.018). Longitudinal risk factors included exposure to fluoroquinolones (OR 3.96, 95% CI 1.04–15.15, P = 0.044), ceftriaxone (OR 18.93, 95% CI 1.27–281.95, P = 0.033) and piperacillin/tazobactam (OR 10.4, 95% CI 1.81–59.64, P = 0.009).Conclusions: Haematology patients exhibit a higher rate of rCDI than general hospitalized patients. Utilization of this multivariable model to guide index CDI therapy at index may help to decrease the rCDI and prevent delays or interruptions in chemotherapy.

Population pharmacokinetics and dosing simulations of ceftazidime in critically ill patients receiving sustained low-efficiency dialysis


Objectives: To describe the population PKs of ceftazidime in critically ill patients receiving sustained low-efficiency dialysis (SLED).Patients and methods: This study was performed in ICUs of a university hospital. We collected blood samples during three consecutive days of SLED sessions in patients receiving ceftazidime. Concentration versus time curves were analysed using a population PKs approach with Pmetrics®. Monte Carlo simulation for the first 24 h including a 6 h SLED session was performed with the final model. The fractional target attainment against the MIC of Pseudomonas aeruginosa was executed using targets of 50 and 100% fT >MIC.Results: In total, 211 blood samples of 16 critically ill patients under SLED were collected. SLED treatments were 299.3 (68.4) min in duration. A two-compartment linear population PK model was most appropriate. The mean (SD) CL of ceftazidime on SLED, and off SLED were 5.32 (3.2), 1.06 (1.0) L/h respectively. The PTA for 50% fT >MIC for a dose of 1 g intravenously every 8 h was 98%. Assuming a target of 100% fT >MIC a dose of 2 g every 12 h covers isolates with MIC ≤8 mg/L with a PTA of 96%.Conclusion: In critically ill patients receiving SLED, ceftazidime 1 g every 8 h and ceftazidime 2 g every 12 h appear to be sufficient for achieving traditional (50% fT >MIC) and aggressive PD targets (100% fT >MIC) for susceptible isolates (MIC ≤8 mg/L), respectively.

Effect of rifampicin and efavirenz on moxifloxacin concentrations when co-administered in patients with drug-susceptible TB


Objectives: We compared the pharmacokinetics of moxifloxacin during rifampicin co-treatment or when dosed alone in African patients with drug-susceptible recurrent TB.Methods: Patients in the intervention arm of the Improving Retreatment Success (IMPRESS) randomized controlled TB trial received 400 mg of moxifloxacin, with rifampicin, isoniazid and pyrazinamide in the treatment regimen. Moxifloxacin concentrations were measured in plasma during rifampicin-based TB treatment and again 4 weeks after treatment completion, when given alone as a single dose. Moxifloxacin concentration–time data were analysed using non-linear mixed-effects models.Results: We included 58 patients; 42 (72.4%) were HIV co-infected and 40 (95%) of these were on efavirenz-based ART. Moxifloxacin pharmacokinetics was best described using a two-compartment disposition model with first-order lagged absorption and elimination using a semi-mechanistic model describing hepatic extraction. Oral clearance (CL/F) of moxifloxacin during rifampicin-based TB treatment was 24.3 L/h for a typical patient (fat-free mass of 47 kg), resulting in an AUC of 16.5 mg·h/L. This exposure was 7.8% lower than the AUC following the single dose of moxifloxacin given alone after TB treatment completion. In HIV-co-infected patients taking efavirenz-based ART, CL/F of moxifloxacin was increased by 42.4%, resulting in a further 30% reduction in moxifloxacin AUC.Conclusions: Moxifloxacin clearance was high and plasma concentrations low in our patients overall. Moxifloxacin AUC was further decreased by co-administration of efavirenz-based ART and, to a lesser extent, rifampicin. The clinical relevance of the low moxifloxacin concentrations for TB treatment outcomes and the need for moxifloxacin dose adjustment in the presence of rifampicin and efavirenz co-treatment need further investigation.

Changes in bone turnover markers with HIV seroconversion and ART initiation


Background: Osteoporosis is common among HIV-infected persons and contributes to risk of fragility fracture. While ART initiation is associated with decreases in bone mineral density and increases in bone turnover, the impact of HIV on bone metabolism is unclear.Methods: We identified men at the Chicago site of the Multicenter AIDS Cohort Study who HIV seroconverted while under observation. Concentrations of 25-OH vitamin D, bone turnover markers [procollagen type 1 N terminal propeptide (P1NP), osteocalcin (OC), C-telopeptide (CTX)] and sclerostin were measured from stored serum obtained at pre-HIV infection, pre-ART and post-ART initiation timepoints. Mixed models, with each biomarker as an outcome, were fitted. Timepoint, age, CD4 count (cells/mm3), HIV-viral suppression, season and an age by timepoint interaction term were considered as fixed effects.Results: Data from 52 participants revealed that median duration between HIV seroconversion and ART initiation was 8.7 years (IQR 3.7–11.6). Median CD4 and plasma HIV-RNA concentrations were 445 (IQR 298.5–689) and 20 184 copies/mL (IQR 6237–64 340), respectively, at the pre-ART timepoint. Multivariate analyses demonstrated pre-HIV infection levels of OC that were higher than pre-ART levels (6.8 versus 5.7 ng/mL, P =0.04); and pre-ART levels of sclerostin that were higher than post-ART levels (0.033 versus 0.02 ng/mL, P <0.001). No changes in P1NP, CTX and 25-OH vitamin D levels were detected.Conclusions: HIV seroconversion was associated with decreased OC levels while ART initiation was associated with decreases in sclerostin, a negative regulator of bone formation. Our results suggest that both HIV infection and ART have an impact on bone metabolism in white men.

Ceftolozane/tazobactam activity against drug-resistant Enterobacteriaceae and Pseudomonas aeruginosa causing urinary tract and intraabdominal infections in Europe: report from an antimicrobial surveillance programme (2012–15)


Objectives: To evaluate the in vitro activity of ceftolozane/tazobactam and comparators tested against European isolates of Enterobacteriaceae and Pseudomonas aeruginosa from hospitalized patients with urinary tract infection or intraabdominal infections.Methods: A total of 6553 Gram-negative organisms (603 P. aeruginosa and 5950 Enterobacteriaceae) were consecutively collected from 41 hospitals located in 17 European countries plus Israel and Turkey. The organisms were tested for susceptibility by broth microdilution methods and the results interpreted according to EUCAST and CLSI breakpoint criteria.Results: Ceftolozane/tazobactam [MIC50/90 0.25/1 mg/L; 93.5%/91.3% susceptible (S) (CLSI/EUCAST criteria)] and meropenem [MIC50/90 ≤0.06/≤0.06 mg/L; 98.1%/98.3% S (CLSI/EUCAST)] were the most active compounds tested against Enterobacteriaceae. Among the Enterobacteriaceae isolates, 1.9% were carbapenem resistant (CRE), 15.2% exhibited an ESBL non-CRE phenotype, 14.6% were MDR, 2.2% were XDR and <0.1% were pan-drug resistant (PDR). Whereas ceftolozane/tazobactam showed activity against ESBL non-CRE phenotype isolates (MIC50/90 0.5/8 mg/L), it lacked useful activity against strains with a CRE (MIC50/90 >32/>32 mg/L; 3.6% S) or PDR (MIC50 >32 mg/L; 0.0% S) phenotype. Ceftolozane/tazobactam was the most potent (MIC50/90 0.5/4 mg/L) β-lactam agent tested against P. aeruginosa isolates, inhibiting 91.7% at an MIC of ≤4 mg/L. P. aeruginosa exhibited high rates of resistance to cefepime (20.6%), ceftazidime (23.1%), meropenem (9.0%) and piperacillin/tazobactam (26.9%) (EUCAST criteria). Among these four P. aeruginosa resistant phenotypes, 61.3%–70.4% were susceptible to ceftolozane/tazobactam.Conclusions: Ceftolozane/tazobactam was the most active β-lactam agent tested against P. aeruginosa and demonstrated higher in vitro activity than currently available cephalosporins and piperacillin/tazobactam when tested against Enterobacteriaceae.

Antimicrobials and QT prolongation


Solithromycin, a ketolide/macrolide antibiotic, has recently been reported to be free of the expected QT-prolonging effect of macrolides. It appears that its keto substitution provides a structural basis for this observation, as the other two tested ketolides also have minimal QT effect.Among non-cardiovascular therapies, antimicrobials probably carry the greatest potential to cause cardiac arrhythmias. This is a result of their propensity to bind to the delayed rectifier potassium channel, IKr, inducing QT prolongation and risk of torsades de pointes ventricular tachycardia, their frequent interference with the metabolism of other QT prolongers and their susceptibility to metabolic inhibition by numerous commonly used drugs.Unfortunately, there is evidence that medical practitioners do not take account of the QT/arrhythmia risk of antimicrobials in their prescribing practices. Education on this topic is sorely needed. When a macrolide is indicated, a ketolide should be considered in patients with a QT risk.

Impact of plasmid-borne oqxAB on the development of fluoroquinolone resistance and bacterial fitness in Escherichia coli


Objectives: To investigate the impact of plasmid-borne oqxAB genes on the development of fluoroquinolone resistance, mutations and bacterial fitness in Escherichia coli.Methods: MICs and mutation prevention concentrations were compared among E. coli strain TOP10 and two corresponding transformants harbouring the OqxAB-encoding plasmids. Mutants were selected by serial passages with the 0.5-fold MIC of ciprofloxacin, and were randomly selected to determine mutations. Bacterial fitness was evaluated by competition assays in vitro and in vivo.Results: The oqxAB-carrying plasmids contributed to a 4–8-fold increase in the ciprofloxacin MIC and increased the ciprofloxacin mutation prevention concentration by 8–16-fold. The MIC of ciprofloxacin for the two transformants increased faster than that of E. coli TOP10 by serial passaging. Novel mutations in gyrB (A468P or F458V) were first observed. Mutations in gyrA were distributed at codons 87 and 83 in the two transformants, whereas mutation A119E in gyrA dominated in the TOP10 mutants. Although the two oqxAB-bearing plasmids caused a decrease in fitness in vitro, their fitness increased when combined with more than one chromosomal mutation, and clear biological benefits were observed in vivo. The mutations in gyrB were associated with a fitness cost, which could be compensated for by additional mutations. The novel mutation gyrA ΔS83 significantly reduced biological fitness both in vitro and in vivo, and was thus quickly replaced by more beneficial mutations in the population.Conclusions: The possession of plasmid-borne oqxAB may facilitate the evolution of fluoroquinolone resistance, and the fitness cost of OqxAB-encoding plasmids could be compensated by additional chromosomal mutations.

Rapid accumulation of HIV-1 thymidine analogue mutations and phenotypic impact following prolonged viral failure on zidovudine-based first-line ART in sub-Saharan Africa


Background: Lack of viral load monitoring of ART is known to be associated with slower switch from a failing regimen and thereby higher prevalence of MDR HIV-1. Many countries have continued to use thymidine analogue drugs despite recommendations to use tenofovir in combination with a cytosine analogue and NNRTI as first-line ART. The effect of accumulated thymidine analogue mutations (TAMs) on phenotypic resistance over time has been poorly characterized in the African setting.Patients and methods: A retrospective analysis of individuals with ongoing viral failure between weeks 48 and 96 in the NORA (Nevirapine OR Abacavir) study was conducted. We analysed 36 genotype pairs from weeks 48 and 96 of first-line ART (14 treated with zidovudine/lamivudine/nevirapine and 22 treated with zidovudine/lamivudine/abacavir). Phenotypic drug resistance was assessed using the Antivirogram assay (v. 2.5.01, Janssen Diagnostics).Results: At 96 weeks, extensive TAMs (≥3 mutations) were present in 50% and 73% of nevirapine- and abacavir-treated patients, respectively. The mean (SE) number of TAMs accumulating between week 48 and week 96 was 1.50 (0.37) in nevirapine-treated participants and 1.82 (0.26) in abacavir-treated participants. Overall, zidovudine susceptibility of viruses was reduced between week 48 [geometric mean fold change (FC) 1.3] and week 96 (3.4, P =0.01). There was a small reduction in tenofovir susceptibility (FC 0.7 and 1.0, respectively, P =0.18).Conclusions: Ongoing viral failure with zidovudine-containing first-line ART is associated with rapidly increasing drug resistance that could be mitigated with effective viral load monitoring.

Chromosomally encoded ESBL genes in Escherichia coli of ST38 from Mongolian wild birds


Objectives: ESBL genes in Escherichia coli are mainly plasmid encoded, although recent studies have also shown chromosomal integration, e.g. in clinical E. coli isolates of ST38. As ESBL-producing E. coli are also found in non-clinical settings, we were interested in determining whether chromosomally integrated ESBL genes occur in ST38 isolates from non-clinical habitats, e.g. wildlife.Methods: Four ESBL-producing E. coli isolates of ST38 originating from Mongolian birds of prey sampled in 2015 were subjected to a detailed analysis in terms of phenotypic resistance, plasmid profiling and WGS, followed by the determination of genotypic resistance factors including the chromosomal integration of ESBL and carbapenemase genes.Results: Results based on phenotypic and genotypic plasmid profiling, contiguous sequence (contig) sizes and PCR analysis of flanking insertion site regions showed that three of four ST38 isolates harboured chromosomally encoded blaCTX-M genes of three different types (blaCTX-M-14, blaCTX-M-15 and blaCTX-M-24) that were inserted into three different chromosomal locations. A comparison of WGS data with ST38 isolates from a clinical outbreak in the UK indicated only low numbers of core-genome SNPs detected among one Mongolian wild bird isolate and eight clinical isolates from the UK.Conclusions: The chromosomal integration of blaCTX-M genes in E. coli isolates of ST38 appears to be common and is likely independent of antimicrobial selective pressure in clinical environments. Our data corroborate the zoonotic potential of environmental isolates of ESBL-producing E. coli, which harbour stably integrated, chromosomally encoded resistance factors.

In vitro activity of the novel echinocandin CD101 at pH 7 and 4 against Candida spp. isolates from patients with vulvovaginal candidiasis


Background: The novel echinocandin CD101 has stability properties amenable to topical formulation for use in the treatment of acute vulvovaginal candidiasis (VVC) and recurrent VVC (RVVC). CD101 has demonstrated potent antifungal activity at pH 7, but assessment of its activity at the physiological pH of the vaginal environment is needed.Objectives: To evaluate the antifungal activity of CD101 against clinical VVC isolates of Candida spp., including azole-resistant strains, at pH 4.Methods: MIC values of CD101 and comparators (fluconazole, itraconazole, micafungin, caspofungin and anidulafungin) were assessed via broth microdilution. MIC assays were conducted at pH 7 and 4 after 24 and 48 h against a 108 VVC isolate panel of Candida spp., including Candida albicans (n =60), Candida glabrata (n =21), Candida parapsilosis (n =14) and Candida tropicalis (n =13).Results: Overall, MIC values of all drugs were slightly higher at pH 4 versus 7 and at 48 versus 24 h of incubation. CD101 MIC values typically exhibited ∼4-fold shifts at pH 4 and were not affected by azole susceptibility. C. parapsilosis susceptibility was the least affected at pH 4 and did not increase for most drugs.Conclusions: CD101 had potent activity against all Candida isolates tested, including azole-resistant strains. Although there was some reduction in activity at pH 4 versus 7, the resulting MIC values were still well below the intravaginal CD101 drug concentrations anticipated to be present following topical administration. These results support continued development of topical CD101 for the treatment of VVC/RVVC.

In vitro activity of cefepime/zidebactam (WCK 5222) against Gram-negative bacteria


Objectives: Diazabicyclooctanes (DBOs) inhibit class A, class C and some class D β-lactamases. A few also bind PBP2, conferring direct antibacterial activity and a β-lactamase-independent ‘enhancer' effect, potentiating β-lactams targeting PBP3. We tested a novel DBO, zidebactam, combined with cefepime.Methods: CLSI agar dilution MICs were determined with cefepime/zidebactam in a chequerboard format. Bactericidal activity was also measured.Results: Zidebactam MICs were ≤2 mg/L (mostly 0.12–0.5 mg/L) for most Escherichia coli, Klebsiella, Citrobacter and Enterobacter spp., but were >32 mg/L for Proteeae, most Serratia and a few E. coli, Klebsiella and Enterobacter/Citrobacter. The antibacterial activity of zidebactam dominated chequerboard studies for Enterobacteriaceae, but potentiation of cefepime was apparent for zidebactam-resistant isolates with class A and C enzymes, illustrating β-lactamase inhibition. Overall, cefepime/zidebactam inhibited almost all Enterobacteriaceae with AmpC, ESBL, K1, KPC and OXA-48-like β-lactamases at 1 + 1 mg/L and also 29 of 35 isolates with metallo-carbapenemases, including several resistant to zidebactam alone. Zidebactam MICs for 36 of 50 Pseudomonas aeruginosa were 4–16 mg/L, and the majority of AmpC, metallo-β-lactamase-producing and cystic fibrosis isolates were susceptible to cefepime/zidebactam at 8 + 8 mg/L. Zidebactam MICs for Acinetobacter baumannii and Stenotrophomonas maltophilia were >32 mg/L; potentiation of cefepime was frequent for S. maltophilia, but minimal for A. baumannii. Kill curve results largely supported MICs.Conclusions: Zidebactam represents a second triple-action DBO following RG6080, with lower MICs for Enterobacteriaceae and P. aeruginosa. Clinical evaluation of cefepime/zidebactam must critically evaluate the reliance that can be placed on this direct antibacterial activity and on the enhancer effect as well as β-lactamase inhibition.

Antibiotic stability related to temperature variations in elastomeric pumps used for outpatient parenteral antimicrobial therapy (OPAT)


Background: Elastomeric pumps can be used for the continuous administration of antimicrobials in the outpatient setting. A potentially limiting factor in their use is the stability of antimicrobials.Objectives: To investigate under real-life conditions the temperature variations of antibiotic solutions contained in elastomeric pumps, and to examine under such conditions the stability of five antibiotics.Methods: Healthy volunteers carried the elastomeric pumps in carry pouches during their daily activities. A thermologger measured the temperatures every 15 min over 24 h. Antibiotic concentrations were measured by HPLC coupled to tandem MS.Results: During daytime, the temperature of solutions in the pumps increased steadily, warming to >30°C. During the night, when the pumps were kept attached to the waist, the temperatures reached up to 33°C. The use of white carry pouches avoided excessive temperature increases. Over seven experiments, cefazolin, cefepime, piperacillin and tazobactam were found to be stable over 24 h. Flucloxacillin showed a mean decrease in concentration of 11% (P = 0.001).Conclusions: Real-life situations can cause significant temperature rises in elastomeric pumps, thereby potentially increasing the risk of antibiotic degradation. Patients should be instructed to avoid situations causing excessive temperature increases. Despite these temperature variations, cefazolin, cefepime, piperacillin and tazobactam were found to be stable over 24 h. A moderate degradation was noticed for flucloxacillin, albeit most probably not to an extent that might impair anti-infective efficacy.

Factors associated with carriage of carbapenem-non-susceptible Enterobacteriaceae in North-Eastern France and outcomes of infected patients


Background: Carbapenems are frequently used as a last resort to treat infections caused by multidrug-resistant Gram-negative organisms, thus carbapenem-non-susceptible Enterobacteriaceae (CNSE) is an emerging health threat.Objectives: To assess risk factors and outcomes of CNSE carriage.Patients and methods: We conducted a matched case–control study in six hospitals in North-Eastern France. The controls were patients harbouring carbapenem-susceptible Enterobacteriaceae. Fifty-five cases and 110 controls were included.Results: Most of the CNSE isolates were Enterobacter cloacae and Klebsiella pneumoniae. Carbapenemase production was observed in 40% of isolates and they produced OXA-48 only. CNSE carriage was significantly associated with recent antibiotic use (P = 0.014), particularly carbapenems (P = 0.03) and fluoroquinolones (P = 0.016). A multivariate analysis using conditional logistic regression showed that the presence of concomitant infection(s) (OR: 9.83; 95% CI 3.04–21.39, P = 0.0031), nosocomial infections (OR: 7.84; 95% CI 2.00–12.54, P =0.0063) and a high age (OR: 1.07; 95% CI 1.01–1.06, P = 0.038) were independently associated with CNSE carriage. Moreover, patients infected with CNSE had worse outcomes: fewer resolved infections at 1 month (P = 0.02), and they had a higher mortality rate (P = 0.0004) and longer hospital stays (P = 0.02).Conclusions: We identified three independent risk factors for CNSE carriage as well as worse outcomes in infected patients in North-Eastern France. This highlights the importance of early detection of CNSE and the need for antimicrobial therapy re-evaluation after bacteriological analysis has been performed.

Increased prescribing of systemic tetracyclines and isotretinoin for treatment of acne


Objectives: To investigate the prescribing of systemic drugs for the treatment of acne in adolescents in the period 2005–15.Methods: The study population consisted of 14–24-year-old users of tetracyclines, isotretinoin or hormonal therapy retrieved from the Norwegian Prescription Database. The 1 year period prevalence was calculated as the number of patients who had redeemed at least one prescription during the year divided by the mean population. If the user had no prescriptions in the preceding 12 months he/she was defined as a new user. The incidence rate was defined by the number of new users during the year divided by the mean population.Results: Increased prescribing rates for systemic tetracyclines and isotretinoin were observed in the period 2005–15, while a decreased prescribing rate for hormonal therapy was observed from 2007. The majority (75%) of the tetracycline prescriptions were prescribed by general practitioner specialists or physicians with no specialty/under training for a specialty. The average durations of treatment in men and women who only used tetracyclines were 3.3 and 2.8 months, respectively. For men and women that switched to isotretinoin, the average durations of treatment were 4.3 and 3.9 months.Conclusions: The increased use of systemic tetracyclines in general, and the prolonged use of tetracyclines in patients who later switch to isotretinoin, raise the question of whether isotretinoin treatment should be considered at an earlier stage to reduce the use of systemic tetracyclines.

Exploring the pharmacodynamic interactions between tedizolid and other orally bioavailable antimicrobials against Staphylococcus aureus and Staphylococcus epidermidis


Objectives: Tedizolid is an orally bioavailable oxazolidinone with once-daily dosing and broad-spectrum Gram-positive activity. Combination therapy is commonly indicated to improve efficacy against difficult-to-treat pathogens and biofilms. There are no studies describing the pharmacodynamic interactions between tedizolid and other orally bioavailable antimicrobials.Methods: MICs of tedizolid, rifampicin, trimethoprim/sulfamethoxazole, doxycycline and moxifloxacin were determined by broth microdilution against a convenience sample of 45 staphylococcal isolates. Seven MRSA isolates and three Staphylococcus epidermidis were evaluated by time–kill using concentrations equal to 0.5× the MIC. These strains had variable susceptibility to the investigated antimicrobials. Synergy was defined as a ≥2 log10 cfu/mL reduction of the combination over the most active single agent, antagonism was defined as ≥1 log10 cfu/mL growth compared with the most active single agent, and other interactions were indifferent.Results: Three of 45 strains tested were non-susceptible to tedizolid (MIC = 1 mg/L), but the MIC90 was 0.5 mg/L. Interactions between tedizolid and other agents were largely indifferent (80%). Tedizolid was synergistic with doxycycline and rifampicin against 2/10 and 3/10 strains, respectively. Tedizolid was antagonistic with moxifloxacin against 3/10 strains. Other interactions were indifferent.Conclusions: The addition of rifampicin to tedizolid appears to be the most likely to improve activity but synergy was not universal. The combination of tedizolid plus moxifloxacin should be avoided due to the risk of antagonism. The addition of other orally bioavailable anti-staphylococcal agents to tedizolid may be unlikely to improve killing but further research is warranted to assess the impact of these combinations on resistance prevention, or against biofilm-embedded organisms.

Determining β-lactam exposure threshold to suppress resistance development in Gram-negative bacteria


Objectives: β-Lactams are commonly used for nosocomial infections and resistance to these agents among Gram-negative bacteria is increasing rapidly. Optimized dosing is expected to reduce the likelihood of resistance development during antimicrobial therapy, but the target for clinical dose adjustment is not well established. We examined the likelihood that various dosing exposures would suppress resistance development in an in vitro hollow-fibre infection model.Methods: Two strains of Klebsiella pneumoniae and two strains of Pseudomonas aeruginosa (baseline inocula of ∼108 cfu/mL) were examined. Various dosing exposures of cefepime, ceftazidime and meropenem were simulated in the hollow-fibre infection model. Serial samples were obtained to ascertain the pharmacokinetic simulations and viable bacterial burden for up to 120 h. Drug concentrations were determined by a validated LC–MS/MS assay and the simulated exposures were expressed as Cmin/MIC ratios. Resistance development was detected by quantitative culture on drug-supplemented media plates (at 3× the corresponding baseline MIC). The Cmin/MIC breakpoint threshold to prevent bacterial regrowth was identified by classification and regression tree (CART) analysis.Results: For all strains, the bacterial burden declined initially with the simulated exposures, but regrowth was observed in 9 out of 31 experiments. CART analysis revealed that a Cmin/MIC ratio ≥3.8 was significantly associated with regrowth prevention (100% versus 44%, P = 0.001).Conclusions: The development of β-lactam resistance during therapy could be suppressed by an optimized dosing exposure. Validation of the proposed target in a well-designed clinical study is warranted.

Antibiotic susceptibility and molecular analysis of invasive Haemophilus influenzae in Canada, 2007 to 2014


Background: Previously we studied the antibiotic susceptibility of invasive Haemophilus influenzae collected in Canada from 1990 to 2006 and characterized isolates by serotype, MLST and ftsI gene sequencing for significant PBP3 mutations.Objectives: To provide an update based on isolates collected from 2007 to 2014.Methods: A total of 882 case isolates were characterized by serotype using slide agglutination and PCR. MLST was carried out to determine ST. Isolates were tested for β-lactamase production, presence of significant PBP3 mutations and antibiotic susceptibility by disc diffusion against 14 antibiotics. MIC values of three antibiotics were determined for 316 isolates using microbroth dilution.Results: Non-typeable H. influenzae accounted for 54.6% of the isolates and 45.4% were serotypeable, predominantly type a (23.1%), type b (8.3%) and type f (10.8%). The overall rate of ampicillin resistance due to β-lactamase production was 16.4% and increased from 13.5% in 2007–10 to 19% in 2011–14. Significant PBP3 mutations were identified in 129 isolates (14.6%) with 23 (2.6%) also producing β-lactamase. MLST identified related STs (ST-136, ST-14 and ST-367) associated exclusively with genetically β-lactamase-negative, ampicillin-resistant isolates and confirmed previously reported associations between significant PBP3 mutations and ST.Conclusions: A significant increase in β-lactamase-producing isolates was observed from 2007 to 2014; the rate of significant PBP3 mutations has increased since previously reported and 52.5% of non-typeable H. influenzae now show resistance markers. Resistance to trimethoprim/sulfamethoxazole was common and no resistance to fluoroquinolones or third-generation cephalosporins was found.

Macrolide resistance in Legionella pneumophila : the role of LpeAB efflux pump


Objectives: A previous study on 12 in vitro-selected azithromycin-resistant Legionella pneumophila lineages showed that ribosomal mutations were major macrolide resistance determinants. In addition to these mechanisms that have been well described in many species, mutations upstream of lpeAB operon, homologous to acrAB in Escherichia coli, were identified in two lineages. In this study, we investigated the role of LpeAB and of these mutations in macrolide resistance of L. pneumophila.Methods: The role of LpeAB was studied by testing the antibiotic susceptibility of WT, deleted and complemented L. pneumophila Paris strains. Translational fusion experiments using GFP as a reporter were conducted to investigate the consequences of the mutations observed in the upstream sequence of lpeAB operon.Results: We demonstrated the involvement of LpeAB in an efflux pump responsible for a macrolide-specific reduced susceptibility of L. pneumophila Paris strain. Mutations in the upstream sequence of lpeAB operon were associated with an increased protein expression. Increased expression was also observed under sub-inhibitory macrolide concentrations in strains with both mutated and WT promoting regions.Conclusions: LpeAB are components of an efflux pump, which is a macrolide resistance determinant in L. pneumophila Paris strain. Mutations observed in the upstream sequence of lpeAB operon in resistant lineages led to an overexpression of this efflux pump. Sub-inhibitory concentrations of macrolides themselves participated in upregulating this efflux and could constitute a first step in the acquisition of a high macrolide resistance level.

Pharmacodynamics of ceftazidime/avibactam against extracellular and intracellular forms of Pseudomonas aeruginosa


Objectives: When tested in broth, avibactam reverses ceftazidime resistance in many Pseudomonas aeruginosa that express ESBLs. We examined whether similar reversal is observed against intracellular forms of P. aeruginosa.Methods: Strains: reference strains; two engineered strains with basal non-inducible expression of AmpC and their isogenic mutants with stably derepressed AmpC; and clinical isolates with complete, partial or no resistance to reversion with avibactam. Pharmacodynamic model: 24 h concentration–response to ceftazidime [0.01–200 mg/L alone or with avibactam (4 mg/L)] of bacteria in broth or bacteria phagocytosed by THP-1 monocytes, with calculation of ceftazidime relative potency (Cs: concentration yielding a static effect) and maximal relative effect [Emax: cfu decrease at infinitely large antibiotic concentrations (efficacy in the model)] using the Hill equation. Cellular content of avibactam: quantification by LC-MS/MS.Results: For both extracellular and intracellular bacteria, ceftazidime Cs was always close to its MIC. For ceftazidime-resistant strains, avibactam addition shifted ceftazidime Cs to values close to the MIC of the combination in broth. Emax was systematically below the detection limit (−5 log10) for extracellular bacteria, but limited to −1.3 log10 for intracellular bacteria (except for two isolates) with no effect of avibactam. The cellular concentration of avibactam reflected extracellular concentration and was not influenced by ceftazidime (0–160 mg/L).Conclusions: The potential for avibactam to inhibit β-lactamases does not differ for extracellular and intracellular forms of P. aeruginosa, denoting an unhindered access to its target in both situations. The loss of maximal relative efficacy of ceftazidime against intracellular P. aeruginosa was unrelated to resistance via avibactam-inhibitable β-lactamases.

Repurposing an old drug: aztreonam as a new treatment strategy for gonorrhoea


Objectives: To determine whether aztreonam is still an effective drug for the treatment of gonorrhoea.Methods: Observational study of patients with gonorrhoea diagnosed by urine multiplex PCR, with a past medical history of allergy to β-lactams or relapse after treatment with a third-generation cephalosporin. Patients received a single 1 g dose of aztreonam in accordance with the manufacturer's instructions.Results: Five patients (four males, one female) were enrolled, comprising two who were allergic to β-lactams and three previously treated with cephalosporins who relapsed. Median age was 38 years (range 23–51). Following treatment with aztreonam all were cured without any adverse event. All the men were free of symptoms, and the woman tested negative for gonorrhoea 1 month after treatment.Conclusion: Aztreonam appears to be an effective alternative to cephalosporins in the treatment of uncomplicated gonorrhoea, particularly when patients are suspected of being infected by strains with reduced susceptibility to ceftriaxone or are known to be allergic to penicillin.

Antimicrobial resistance in uropathogens and appropriateness of empirical treatment: a population-based surveillance study in Indonesia


Objectives: Urinary tract infections (UTIs) are a common reason for empirical treatment with broad-spectrum antibiotics worldwide. However, population-based antimicrobial resistance (AMR) prevalence data to inform empirical treatment choice are lacking in many regions, because of limited surveillance capacity. We aimed to assess the prevalence of AMR to commonly used antimicrobial drugs in Escherichia coli and Klebsiella pneumoniae isolated from patients with community- or healthcare-associated UTIs on two islands of Indonesia.Methods: We performed a cross-sectional patient-based study in public and private hospitals and clinics between April 2014 and May 2015. We screened patients for symptoms of UTIs and through urine dipstick analysis. Urine culture and susceptibility testing were supported by telemicrobiology and interactive virtual laboratory rounds. Surveillance data were entered in forms on mobile phones.Results: Of 3424 eligible patients, 3380 (98.7%) were included in the final analysis, and yielded 840 positive cultures and antimicrobial susceptibility data for 657 E. coli and K. pneumoniae isolates. Fosfomycin was the single oral treatment option with resistance prevalence <20% in both E. coli and K. pneumoniae in community settings. Tigecycline and fosfomycin were the only options for treatment of catheter-associated UTIs with resistance prevalence <20%, whilst the prevalence of resistance to meropenem was 21.3% in K. pneumoniae.Conclusions: Patient-based surveillance of AMR in E. coli and K. pneumoniae causing UTIs indicates that resistance to the commonly available empirical treatment options is high in Indonesia. Smart AMR surveillance strategies are needed to inform policy makers and to guide interventions.

Environmental emission of multiresistant Escherichia coli carrying the colistin resistance gene mcr-1 from German swine farms


Objectives: Pigs have been the focus of the worldwide spread of colistin resistance. However, there is little information on the transmission of mcr-1-containing bacteria into the environment of pig farms. We therefore rescreened environmental Escherichia coli isolates from the surrounding farm areas of three previously mcr-1-positive swine herds in Germany.Methods: Thirty-five mixed bacterial cultures obtained from boot swabs, flies, dog faeces and manure from three pig farms in Germany in 2011–12 were non-selectively recultivated and the presence of the mcr-1 gene was checked by real-time PCR. After separation, single E. coli colonies were subsequently isolated and the presence of mcr-1 was confirmed by PCR and sequencing. In addition, phenotypic antimicrobial resistance screening and WGS followed by phylogenetic analysis and resistance genotyping as well as plasmid typing were performed.Results: Seven mcr-1-positive E. coli strains originating from environmental boot swabs, dog faeces, stable flies and manure were found. The isolates belonged to five different STs (ST10, ST1011, ST1140, ST5281 and ST342) and harboured extensive additional resistance genes. Comparative plasmid analysis predominantly located mcr-1 on IncX4 plasmids, which are strongly related to a recently described plasmid of human clinical origin (pICBEC72Hmcr).Conclusions: WGS-based analysis of the environmental E. coli isolates of farm surroundings showed clear links to mcr-1-harbouring E. coli recovered from pig production in Europe as well as from human clinical isolates worldwide, presenting another piece of the puzzle, which further complicates the rapidly evolving epidemiology of plasmid-mediated colistin-resistant E. coli strains.

Epidemiology and susceptibility of pathogens from SMART 2011–12 Turkey: evaluation of hospital-acquired versus community-acquired urinary tract infections and ICU- versus non-ICU-associated intra-abdominal infections


Objectives: To describe the epidemiology and susceptibility of pathogens (including ESBL producers) from hospital-acquired (HA) versus community-acquired (CA) urinary tract infections (UTIs) and ICU- versus non-ICU-associated intra-abdominal infections (IAIs) in Turkey as a part of the SMART study.Methods: For this report, Gram-negative pathogens (363 from UTIs and 458 from IAIs) were collected in 2011 and 2012 at six hospitals in Turkey. HA versus CA UTIs and ICU- versus non-ICU-associated IAIs were compared for the species isolated, percentage of ESBL-positive isolates by species and susceptibility for overall and individual Gram-negative species.Results: Escherichia coli was the most common pathogen identified in HA (40.2%) and CA (73.9%) UTIs and ICU-associated (25.8%) and non-ICU-associated (43.3%) IAIs. The rate of ESBL-positive E. coli was significantly higher in HA than in CA UTIs (50.5% versus 38.2%, P <0.001) and in non-ICU-associated than in ICU-associated IAIs (52.5% versus 29.2%, P = 0.029). Of the drugs studied, only amikacin was active against ≥90% of pathogens in UTIs, while ertapenem, imipenem and amikacin were active against ≥90% of E. coli; and imipenem, amikacin and cefoxitin were active against ≥90% of Klebsiella pneumoniae in IAIs.Conclusions: Our findings demonstrated that E. coli continues to be the principal pathogen of UTIs and IAIs in Turkey. Along with a high rate of ESBL-positive isolates, high antimicrobial resistance among Gram-negative bacilli from either UTIs or IAIs was noted particularly in the case of HA UTIs and ICU-associated IAIs, with a higher likelihood of carbapenem- or amikacin-based therapy to provide the broadest activity against bacterial pathogens.

Diversity and functionality of plasmid-borne VagCD toxin–antitoxin systems of Klebsiella pneumoniae


Objectives: To explore the VagCD toxin–antitoxin (TA) systems encoded on plasmids in multiresistant Klebsiella pneumoniae strains.Methods: Previously sequenced K. pneumoniae plasmids were used for in silico analysis and a collection of 63 resistant K. pneumoniae strains was used for epidemiological study. Functional analysis was done after separate cloning of the toxin gene under the control of the arabinose-inducible promoter of pBAD43 and of the antitoxin gene under the control of the constitutive promoter of pUC19.Results:In silico, two types of VagCD systems, VagCD1 and VagCD2, encoded on K. pneumoniae plasmids could be distinguished, 15% carrying one of these TA systems. Moreover, in a collection of antibiotic-resistant K. pneumoniae strains including ESBL or carbapenemase producers, 17.5% of isolates were found to harbour a VagCD TA system. VagCD1 and VagCD2 were proved functional TA systems, with VagD the toxin and VagC its antitoxin, not only in K. pneumoniae but also in Escherichia coli and other Enterobacteriaceae. Toxin expression was found to induce a significant decrease in a bacterial population resulting from both bactericidal and bacteriostatic effects.Conclusions: The vagCD genes of K. pneumoniae encode a functional broad-spectrum TA system and are conserved on the large multiple antibiotic resistance-conferring plasmids in this species.

Rapid direct detection of carbapenemase-producing Enterobacteriaceae in clinical urine samples by MALDI-TOF MS analysis


Objectives: Development of an automated MALDI-TOF MS-based method for the rapid, direct detection of carbapenemase-producing Enterobacteriaceae in clinical urine samples within 90 min of sample reception.Methods: A total of 3041 urine samples were processed by flow cytometry, and a cut-off value of ≥1.5 × 105 bacteria/mL was used to select samples for the study. Following these criteria, 608 samples were selected for direct bacterial identification. Detection of carbapenemase activity by MALDI-TOF MS analysis was only performed after reliable direct identification of Gram-negative bacilli. A novel protocol was developed for extracting bacteria from urine samples by using the Sepsityper Kit (Bruker Daltonik, Germany). Carbapenem resistance was detected with imipenem as an antibiotic marker and the results were automatically interpreted using the STAR-BL module of MALDI-TOF Biotyper Compass software (Bruker Daltonik, Germany).Results: The MALDI-TOF MS-based assay yielded direct reliable identification of 91% (503/553) of the samples. The assay showed 100% sensitivity (30/30) and specificity (454/454) for detecting carbapenemase activity within 90 min of sample reception. Isolates included in the study were further characterized by PCR and sequencing, and blaOXA-48 was detected from all isolates that tested positive in the MALDI-TOF MS-based resistance assay.Conclusions: The proposed protocol for the direct analysis of urine samples by MALDI-TOF MS is suitable for use in clinical laboratories to identify bacteria and detect carbapenemase activity, thus saving at least 24–48 h relative to current routine methods.

Re-emergence of methicillin susceptibility in a resistant lineage of Staphylococcus aureus


Objectives: MRSA is a leading cause of hospital-associated infection. Acquired resistance is encoded by the mecA gene or its homologue mecC, but little is known about the evolutionary dynamics involved in gain and loss of resistance. The objective of this study was to obtain an expanded understanding of Staphylococcus aureus methicillin resistance microevolution in vivo, by focusing on a single lineage.Methods: We compared the whole-genome sequences of 231 isolates from a single epidemic lineage [clonal complex 30 (CC30) and spa-type t018] of S. aureus that caused an epidemic in the UK.Results: We show that resistance to methicillin in this single lineage was gained on at least two separate occasions, one of which led to a clonal expansion around 1995 presumably caused by a selective advantage. Resistance was, however, subsequently lost in vivo by nine strains isolated between 2008 and 2012. We describe the genetic mechanisms involved in this loss of resistance and the imperfect relationship between genotypic and phenotypic resistance.Conclusions: The recent re-emergence of methicillin susceptibility in this epidemic lineage suggests a significant fitness cost of resistance and reduced selective advantage following the introduction in the mid-2000s of MRSA hospital control measures throughout the UK.

In vitro susceptibility to 19 agents other than β-lactams among third-generation cephalosporin-resistant Enterobacteriaceae recovered on hospital admission


Objectives: As part of the multicentre Antibiotic Therapy Optimisation Study, MIC values of 19 non-β-lactam agents were determined for third-generation cephalosporin-resistant Escherichia coli, Klebsiella species and Enterobacter species (3GCREB) isolates collected in German hospitals.Methods: A total of 328 E. coli, 35 Klebsiella spp. (1 Klebsiella oxytoca and 34 Klebsiella pneumoniae) and 16 Enterobacter spp. (1 Enterobacter aerogenes and 15 Enterobacter cloacae) isolates were submitted to broth microdilution antimicrobial susceptibility testing with the MICRONAUT system. MICs of fluoroquinolones (levofloxacin and moxifloxacin), aminoglycosides (gentamicin, tobramycin, amikacin, streptomycin, neomycin and paromomycin), tetracyclines (tetracycline, minocycline and tigecycline), macrolides (erythromycin, clarithromycin and azithromycin) and miscellaneous agents [trimethoprim/sulfamethoxazole, chloramphenicol, nitrofurantoin, colistin and fosfomycin intravenous (iv)] were determined and reviewed against 2016 EUCAST breakpoints.Results: The MIC of levofloxacin was >2 mg/L for 128 of 328 E. coli and 8 of 35 Klebsiella spp., but only 1 of 16 Enterobacter spp. Rates of resistance to trimethoprim/sulfamethoxazole were high (>70%), except for Enterobacter spp. Rates of resistance to colistin and fosfomycin iv were still low. About 20% of the tested isolates were resistant to chloramphenicol. Only 1 (of 328) E. coli isolate had an MIC of amikacin >16 mg/L and only 33 of 328 E. coli and 1 of 35 Klebsiella spp. had an MIC of tobramycin >4 mg/L, whereas average gentamicin MICs were in general more elevated. A tigecycline MIC >2 mg/L was only found for 1 of 16 Enterobacter spp., but in none of the E. coli or Klebsiella spp. isolates.Conclusions: Our study gives insight into previously unreport[...]

Surveillance of antimicrobial use in Dutch long-term care facilities


Objectives: Residents living in a long-term care facility (LTCF) are more susceptible to infections. Treatment with antimicrobials is sometimes necessary; however, antibiotic use is considered one of the most important drivers of the development of antibiotic resistance. Surveillance data on antibiotic use in these LTCFs are necessary to get more insight into these patterns. The objective of this study was to describe antibiotic use in LTCFs in the Netherlands.Methods: One hundred and seventy-seven LTCFs in the Netherlands were contacted and asked to participate in a study concerning antibiotic resistance and antibiotic use. Associated pharmacies were asked to provide data about systemic antibiotic use for each participating LTCF location over 1 year. Results on antibiotic use are reported here.Results: Antibiotic use data from 96 LTCFs were collected from the pharmacies, and 68 of these LTCFs completed additional questionnaires on general characteristics of their location. Mean total use of systemic antimicrobials was 73 DDDs/1000 residents per day (range 2–197 DDDs/1000 residents per day). Co-amoxiclav (23 DDDs/1000 residents/day, range 0–70) was used the most, followed by nitrofurantoin derivatives (12 DDDs/1000 residents/day, range 0–38) and fluoroquinolones (12 DDDs/1000 residents/day, range 0–52). Statistical analysis revealed no significant correlations between the LTCF characteristics and the level of antibiotic use.Conclusions: There was a high use of broad-spectrum antimicrobials, with a large variation in total antibiotic use between individual locations. Further analysis of more in-depth data and possible influencing factors is needed.

Molecular insights into fosfomycin resistance in Escherichia coli


Objectives: Fosfomycin activity in Escherichia coli depends on several genes of unknown importance for fosfomycin resistance. The objective was to characterize the role of uhpT, glpT, cyaA and ptsI genes in fosfomycin resistance in E. coli.Methods: WT E. coli BW25113 and null mutants, ΔuhpT, ΔglpT, ΔcyaA, ΔptsI, ΔglpT-uhpT, ΔglpT-cyaA, ΔglpT-ptsI, ΔuhpT-cyaA, ΔuhpT-ptsI and ΔptsI-cyaA, were studied. Susceptibility to fosfomycin was tested using CLSI guidelines. Fosfomycin mutant frequencies were determined at concentrations of 64 and 256 mg/L. Fosfomycin in vitro activity was tested using time–kill assays at concentrations of 64 and 307 mg/L (human Cmax).Results: Fosfomycin MICs were: WT E. coli BW25113 (2 mg/L), ΔglpT (2 mg/L), ΔuhpT (64 mg/L), ΔcyaA (8 mg/L), ΔptsI (2 mg/L), ΔglpT-uhpT (256 mg/L), ΔglpT-cyaA (8 mg/L), ΔglpT-ptsI (2 mg/L), ΔuhpT-cyaA (512 mg/L), ΔuhpT-ptsI (64 mg/L) and ΔptsI-cyaA (32 mg/L). In the mutant frequency assays, no mutants were recovered from BW25113. Mutants appeared in ΔglpT, ΔuhpT, Δ Dissemination of bla OXA-58 in Proteus mirabilis isolates from Germany


Objectives: Characterization of Proteus mirabilis isolates harbouring blaOXA-58 with emphasis on the genetic environment of this resistance determinant.Methods: Strains of P. mirabilis (n =37) isolated from different patients were tested for the presence of blaOXA-58. The genetic context of blaOXA-58 was determined by WGS of two strains and Sanger sequencing. Clonality of the strains was assessed by PFGE. Susceptibility testing was performed by microdilution according to EUCAST.Results: Four strains isolated in different geographical regions of Germany were positive for blaOXA-58, and WGS showed that this resistance gene was harboured on a plasmid. Sanger sequencing confirmed the presence of two nearly identical plasmids, 6219 and 6208 bp in size, in all four strains. Upstream of blaOXA-58 an ISAba3-like transposase gene was located. The P. mirabilis strains were not clonally related according to PFGE. MICs of meropenem for three of the strains were only just above the EUCAST breakpoint and the Carba NP test was positive for only two of the strains.Conclusions: To our knowledge, this is the first description of blaOXA-58 in the species P. mirabilis. The resistance gene is harboured by almost identical plasmids in strains not clonally related and from different geographical regions. Apart from an ISAba3-like transposase gene upstream of blaOXA-58 the genetic context is different from blaOXA-58 harboured on plasmids in the genus Acinetobacter. With MICs of meropenem well below the EUCAST breakpoint or only just above it and equivocal or false negative results from the Carba NP test, bla<[...]

MIC of amoxicillin/clavulanate according to CLSI and EUCAST: discrepancies and clinical impact in patients with bloodstream infections due to Enterobacteriaceae


Objectives: To compare results of amoxicillin/clavulanate susceptibility testing using CLSI and EUCAST methodologies and to evaluate their impact on outcome in patients with bacteraemia caused by Enterobacteriaceae.Patients and methods: A prospective observational cohort study was conducted in 13 Spanish hospitals. Patients with bacteraemia due to Enterobacteriaceae who received empirical intravenous amoxicillin/clavulanate treatment for at least 48 h were included. MICs were determined following CLSI and EUCAST recommendations. Outcome variables were: failure at the end of treatment with amoxicillin/clavulanate (FEAMC); failure at day 21; and 30 day mortality. Classification and regression tree (CART) analysis and logistic regression were performed.Results: Overall, 264 episodes were included; the urinary tract was the most common source (64.7%) and Escherichia coli the most frequent pathogen (76.5%). Fifty-two isolates (19.7%) showed resistance according to CLSI and 141 (53.4%) according to EUCAST. The kappa index for the concordance between the results of both committees was only 0.24. EUCAST-derived, but not CLSI-derived, MICs were associated with failure when considered as continuous variables. CART analysis suggested a ‘resistance’ breakpoint of > 8/4 mg/L for CLSI-derived MICs; it predicted FEAMC in adjusted analysis (OR = 1.96; 95% CI: 0.98–3.90). Isolates with EUCAST-derived MICs >16/2 mg/L independently predicted FEAMC (OR = 2.10; 95% CI: 1.05–4.21) and failure at day 21 (OR= 3.01; 95% CI: 0.93–9.67). MICs >32/2 mg/L were only predictive of failure among patients with bacteraemia from urinary or biliary tract sources.Conclusions: CLSI and EUCAST methodologies showed low agreement for determining the MIC of amoxicillin/clavulanate. EUCAST-derived MICs seemed more predictive of failure than CLSI-derived ones. EUCAST-derived MICs >16/2 mg/L were independently associated with therapeutic failure.

In vitro activity of ceftazidime/avibactam against urinary isolates from patients in a Phase 3 clinical trial programme for the treatment of complicated urinary tract infections


Objectives: To evaluate the in vitro activity of ceftazidime/avibactam relative to comparator agents against Gram-negative isolates from a Phase 3 clinical trial programme for complicated urinary tract infections (RECAPTURE).Methods: The in vitro activity of ceftazidime/avibactam was evaluated against 840 Gram-negative pathogens isolated at baseline from 1033 randomized patients in two pivotal Phase 3 clinical trials for the treatment of complicated urinary tract infections. The trials were conducted in 160 institutions from 25 countries worldwide. Susceptibility testing was performed by broth microdilution at a central laboratory according to CLSI methodologies.Results: Overall, ceftazidime/avibactam showed significant activity against the Enterobacteriaceae and Pseudomonas aeruginosa with MIC90 values of 0.5 and 8 mg/L, respectively. Against the most common Enterobacteriaceae, MIC90 values were 0.25 mg/L for Escherichia coli, 1 mg/L for Klebsiella pneumoniae, 0.06 mg/L for Proteus mirabilis and 2 mg/L for Enterobacter cloacae. The ceftazidime/avibactam MIC90 for 154 ceftazidime-non-susceptible isolates of Enterobacteriaceae was 1 mg/L and the ceftazidime/avibactam MIC90 for 15 non-susceptible isolates of P. aeruginosa was 64 mg/L. There was a significant reduction in the ceftazidime/avibactam MIC relative to ceftazidime alone for most of the Enterobacteriaceae isolates.Conclusions: The ceftazidime/avibactam in vitro activity against these clinical urinary tract isolates demonstrates the potential utility of the drug in complicated urinary tract infections.

Pharmacokinetic study of anidulafungin in ICU patients with intra-abdominal candidiasis


Background: Only limited pharmacokinetic data are available for anidulafungin in ICU patients, especially in patients treated for severe intra-abdominal infection (IAI).Methods: This was a prospective multicentre observational study in ICU patients with suspected yeast IAI. All patients received an intravenous loading dose of 200 mg of anidulafungin, followed by 100 mg/day. Thirteen blood samples were drawn between day 1 and day 5 for pharmacokinetic analysis. Samples were analysed by an HPLC-tandem MS method. Demographics and SAPS2 and SOFA scores were recorded.Results: Fourteen patients with a median age (IQR) of 62 years (48–70) and with a mean BMI of 30.5 kg/m2 were included from three centres; 57.1% were women. Their median (IQR) SAPS2 score was 54 (45–67) and their median (IQR) SOFA score was 8 (7–12). Six patients with community-acquired IAI and eight patients with nosocomial-acquired IAI were included. Twelve yeasts were isolated: six Candida albicans, two Candida glabrata, two Candida tropicalis, one Candida parapsilosis and one Candida krusei. Pharmacokinetic parameters were as follows [mean (% coefficient of variation)]: Cmax (mg/L) = 6.0 (29%); Tmax (h) = 1.6 (25.8%); Cmin (mg/L) = 3.2 (36.8%); AUC0–24 (mg·h/L) = 88.9 (38.6%); t1/2 (h) = 42.1 (68.2%); CL (L/h) = 1.2 (42.3%); and V (L) = 72.8 (87.8%). A two-compartment model best described the anidulafungin concentrations in the population pharmacokinetic study.Conclusions: The pharmacokinetic parameters of anidulafungin in critically ill ICU patients with complicated IAI are similar to those observed in the literature. However, an increased V and a longer t1/2 were observed in this study. (EudraCT No. 2010-018695-25)

DNA replication proteins as potential targets for antimicrobials in drug-resistant bacterial pathogens


With the impending crisis of antimicrobial resistance, there is an urgent need to develop novel antimicrobials to combat difficult infections and MDR pathogenic microorganisms. DNA replication is essential for cell viability and is therefore an attractive target for antimicrobials. Although several antimicrobials targeting DNA replication proteins have been developed to date, gyrase/topoisomerase inhibitors are the only class widely used in the clinic. Given the numerous essential proteins in the bacterial replisome that may serve as a potential target for inhibitors and the relative paucity of suitable compounds, it is evident that antimicrobials targeting the replisome are underdeveloped so far. In this review, we report on the diversity of antimicrobial compounds targeting DNA replication and highlight some of the challenges in developing new drugs that target this process.