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Preview: Journal of Antimicrobial Chemotherapy - Advance Access

Journal of Antimicrobial Chemotherapy Advance Access

Published: Mon, 18 Sep 2017 00:00:00 GMT

Last Build Date: Mon, 18 Sep 2017 08:49:10 GMT


Optimal cure rate by personalized HCV regimens in real-life: a proof-of-concept study


Background: Pretreatment evaluation of HCV-infected patients is a complex interplay between multiple clinical and viral parameters, leading to a tailored approach that may bring real-life sustained virological response (SVR) rates close to 98%–99%.Objectives: As proof-of-concept, we evaluated the efficacy of all-oral direct-acting antiviral (DAA) regimens in patients whose personalization included pre-therapy evaluation of natural resistance-associated substitutions (RASs), in addition to international guideline recommendations.Methods: One hundred and thirty-one patients who started a first-line all-oral DAA regimen between April 2015 and December 2016 were tested for baseline NS3 and NS5A RASs by Sanger sequencing. SVR12 was defined as HCV-RNA undetectability 12 weeks after treatment discontinuation.Results: Compatibly with a real-life context, 74.0% (97 of 131) of patients presented ≥2 pretreatment risk factors for failure to achieve SVR12 (infection by GT-1a/GT-3a; cirrhosis; previous treatment experience; HCV-RNA ≥800 000 IU/mL) and 33.6% had ≥3 risk factors. Natural RASs were frequently detected (32.1% prevalence), with substantial prevalence of NS5A RASs (15.3%), mostly represented by Y93H in GT-1b (3 of 36, 8.3%) and GT-3a (3 of 25, 12.0%) and F28C in GT-2c (2 of 11, 18.2%). Overall, personalized treatment led to 100% SVR12, even in those patients for whom treatment strategy was either strengthened (by ribavirin inclusion and/or duration increase) or simplified (by ribavirin exclusion and/or duration reduction), thanks to baseline RAS evaluation.Conclusions: Even with newer DAA regimens, an integrated interpretation of clinical and virological pretreatment parameters, including natural RASs, may play a relevant role in bringing SVR rates close to the highest achievable. Treatment tailoring can be foreseen in ‘hard-to-treat’ patients, but also in ‘easy’ patients with favourable indicators, whereby a simplification/shortening of recommended regimens can be indicated.

Impact of amoxicillin resistance on the efficacy of amoxicillin-containing regimens for Helicobacter pylori eradication: analysis of five randomized trials


Background: The impact of amoxicillin resistance on the efficacy of regimens containing amoxicillin for Helicobacter pylori eradication remains unknown.Objectives: To investigate whether the efficacy of an amoxicillin-containing regimen is affected by amoxicillin resistance and to identify the optimal breakpoint for amoxicillin resistance.Methods: This was a pooled analysis of five randomized trials conducted in Taiwan from 2007 to 2016. Patients who received amoxicillin-containing regimens were recruited. MICs were determined by agar dilution testing. Meta-analysis was performed to assess the risk ratio of eradication failure in amoxicillin-resistant strains compared with susceptible strains of seven different regimens. We performed further the pooled analysis and logistic regression in patients treated with clarithromycin triple therapy to identify the optimal breakpoint for amoxicillin resistance. Results: A total of 2339 patients with available amoxicillin MICs were enrolled. Meta-analysis showed that the presence of amoxicillin resistance was consistently associated with increased risk of treatment failure of amoxicillin-containing regimens at different breakpoints (risk ratio: 1.41, 95% CI 1.12–1.78, P = 0.004 when the cut-off was 0.5 mg/L). The heterogeneity was low (I2=0%, P =0.615). Pooled analysis also showed that amoxicillin resistance was an independent risk factor for treatment failure of clarithromycin triple therapy at different breakpoints. The best correlation was observed when the breakpoint of amoxicillin resistance was ≥0.125 mg/L (kappa coefficient 0.298), at which the resistance rate was 11.1% (110 of 990).Conclusions: The efficacies of amoxicillin-containing regimens are affected by amoxicillin resistance and the optimal breakpoint MIC is ≥ 0.125 mg/L.

Trends and patterns in antibiotic prescribing among out-of-hours primary care providers in England, 2010–14


Objectives: Antimicrobial resistance is a global threat, increasing morbidity and mortality. In England, publicly funded clinical commissioning groups (CCGs) commission out-of-hours (OOH) primary care services outside daytime hours. OOH consultations represent 1% of in-hours general practice (GP) consultations. Antibiotic prescriptions increased 32% in non-GP community services between 2010 and 2013. We describe OOH antibiotic prescribing patterns and trends between 2010 and 2014.Methods: We: estimated the proportion of CCGs with OOH data available; described and compared antibiotic prescribing by volume of prescribed items, seasonality and trends in GP and OOH, using linear regression; and compared the proportion of broad-spectrum to total antibiotic prescriptions in OOHs with their respective CCGs in terms of seasonality and trends, using binomial regression.Results: Data were available for 143 of 211 (68%) CCGs. OOH antibiotic prescription volume represented 4.5%–5.4% of GP prescription volume and was stable over time (P =0.37). The proportion of broad-spectrum antibiotic prescriptions increased in OOH when it increased in the CCG they operated in (regression coefficient 0.98; 95% CI 0.96–0.99). Compared with GP, the proportion of broad-spectrum antibiotic prescriptions in OOH was higher but decreased both in GP and OOH (−0.57%, 95% CI − 0.54% to − 0.6% and −0.76%, 95% CI − 0.59% to − 0.93% per year, respectively).Conclusions: OOH proportionally prescribed more antibiotics than GPs although we could not comment on prescribing appropriateness. OOH prescribing volume was stable over time, and followed GP seasonal patterns. OOH antibiotic prescribing reflected the CCGs they operated in but with relatively more broad-spectrum antibiotics than in-hours GP. Understanding factors influencing prescribing in OOH will enable the development of tailored interventions promoting optimal prescribing in this setting.

Evaluation of minor groove binders (MGBs) as novel anti-mycobacterial agents and the effect of using non-ionic surfactant vesicles as a delivery system to improve their efficacy


Objectives: The slow development of major advances in drug discovery for the treatment of Mycobacterium tuberculosis (Mtb) infection suggests a compelling need for evaluation of more effective drug therapies against TB. New classes of drugs are constantly being evaluated for anti-mycobacterial activity with currently a very limited number of new drugs approved for TB treatment. Minor groove binders (MGBs) have previously revealed promising antimicrobial activity against various infectious agents; however, they have not yet been screened against Mtb.Methods: The mycobactericidal activity of 96 MGB compounds against Mtb was determined using an H37Rv-GFP microplate assay. MGB hits were screened for their intracellular mycobactericidal efficacy against the clinical Beijing Mtb strain HN878 in bone-marrow-derived macrophages using standard cfu counting. Cell viability was assessed by CellTiter-Blue assays. Selected MGBs were encapsulated into non-ionic surfactant vesicles (NIVs) for drug delivery system evaluation.Results: H37Rv-GFP screening yielded a hit-list of seven compounds at an MIC99 of between 0.39 and 1.56 μM. MGB-362 and MGB-364 displayed intracellular mycobactericidal activity against Mtb HN878 at an MIC50 of 4.09 and 4.19 μM, respectively, whilst being non-toxic. Subsequent encapsulation into NIVs demonstrated a 1.6- and 2.1-fold increased intracellular mycobacterial activity, similar to that of rifampicin when compared with MGB-alone formulation.Conclusions: MGB anti-mycobacterial activities together with non-toxic properties indicate that MGB compounds constitute an important new class of drug/chemical entity, which holds promise in future anti-TB therapy. Furthermore, the ability of NIVs to better deliver entrapped MGB compounds to an intracellular Mtb infection suggests further preclinical evaluation is warranted.

Identification of a novel transposon-associated phosphoethanolamine transferase gene, mcr-5 , conferring colistin resistance in d -tartrate fermenting Salmonella enterica subsp. enterica serovar Paratyphi B


Objectives: Plasmid-mediated mobilized colistin resistance is currently known to be caused by phosphoethanolamine transferases termed MCR-1, MCR-2, MCR-3 and MCR-4. However, this study focuses on the dissection of a novel resistance mechanism in mcr-1-, mcr-2- and mcr-3-negative d-tartrate fermenting Salmonella enterica subsp. enterica serovar Paratyphi B (Salmonella Paratyphi B dTa+) isolates with colistin MIC values >2 mg/L.Methods: A selected isolate from the strain collection of the German National Reference Laboratory for Salmonella was investigated by WGS and bioinformatical analysis to identify novel phosphoethanolamine transferase genes involved in colistin resistance. Subsequently PCR screening, S1-PFGE and DNA-DNA hybridization were performed to analyse the prevalence and location of the identified mcr-5 gene. Cloning and transformation experiments in Escherichia coli DH5α and Salmonella Paratyphi B dTa+ control strains were carried out and the activity of MCR-5 was determined in vitro by MIC testing.Results: In this study, we identified a novel phosphoethanolamine transferase in 14 mcr-1-, mcr-2- and mcr-3-negative Salmonella Paratyphi B dTa+ isolates with colistin MIC values >2 mg/L that were received during 2011–13. The respective gene, further termed as mcr-5 (1644 bp), is part of a 7337 bp transposon of the Tn3 family and usually located on related multi-copy ColE-type plasmids. Interestingly, in one isolate an additional subclone with a chromosomal location of the mcr-5 transposon was observed.Conclusions: Our findings suggest that the transfer of colistin-resistance-mediating phosphoethanolamine transferase genes from bacterial chromosomes to mobile genetic elements has occurred in multiple independent events raising concern regarding their variety, prevalence and impact on public health.

Modelling of mycobacterial load reveals bedaquiline’s exposure–response relationship in patients with drug-resistant TB


Background: Bedaquiline has been shown to reduce time to sputum culture conversion (SCC) and increase cure rates in patients with drug-resistant TB, but the influence of drug exposure remains uncharacterized.Objectives: To investigate whether an exposure–response relationship could be characterized by making better use of the existing information on pharmacokinetics and longitudinal measurements of mycobacterial load.Methods: Quantitative culture data in the form of time to positivity (TTP) in mycobacterial growth indicator tubes obtained from a randomized placebo-controlled Phase IIb registration trial were examined using non-linear mixed-effects methodology. The link to individual bedaquiline exposures and other patient characteristics was evaluated.Results: The developed model included three simultaneously fitted components: a longitudinal representation of mycobacterial load in patients, a probabilistic component for bacterial presence in sputum samples, and a time-to-event model for TTP. Data were described adequately, and time to SCC was well predicted. Individual bedaquiline exposure was found to significantly affect the decline in mycobacterial load. Consequently, the proportion of patients without SCC at week 20 is expected to decrease from 25% (95% CI 20%–31%) without bedaquiline to 17% (95% CI 13%–21%), 12% (95% CI 8%–16%) and 7% (95% CI 4%–11%), respectively, with half the median, median and double the median bedaquiline exposure observed in patients with standard dosing. Baseline bacterial load and level of drug resistance were other important predictors.Conclusions: To our knowledge, this is the first successful description of bedaquiline’s exposure–response relationship and may be used when considering dose optimization. Characterization of this relationship was possible by integrating quantitative information in existing clinical data using novel models.