Comparison of Six Phenotypic Assays with Reference Methods for Assessing Colistin Resistance in Clinical Isolates of Carbapenemase-Producing Enterobacterales: Challenges and Opportunities.

The global escalation of severe infections due to carbapenemase-producing Enterobacterales (CPE) isolates has prompted increased usage of parenteral colistin. Considering the reported difficulties in assessing their susceptibility to colistin, the purpose of the study was to perform a comparative evaluation of six phenotypic assays-the colistin broth disc elution (CBDE), Vitek 2 Compact (bioMérieux SA, Marcy l'Etoile, France), the Micronaut MIC-Strip Colistin (Merlin Diagnostika GMBH, Bornheim-Hensel, Germany), the gradient diffusion strip Etest (bioMérieux SA, Marcy l'Etoile, France), ChromID Colistin R Agar (COLR) (bioMérieux SA, Marcy l'Etoile, France), and the Rapid Polymyxin NP Test (ELITechGroup, Signes, France)-versus the reference method of broth microdilution (BMD). All false resistance results were further assessed using population analysis profiling (PAP). Ninety-two nonrepetitive clinical CPE strains collected from two hospitals were evaluated. The BMD confirmed 36 (39.13%) isolates susceptible to colistin. According to the BMD, the Micronaut MIC-Strip Colistin, the CBDE, and the COLR medium exhibited category agreement (CA) of 100%. In comparison with the BMD, the highest very major discrepancy (VMD) was noted for Etest (n = 15), and the only false resistance results were recorded for the Rapid Polymyxin NP Test (n = 3). Only the PAP method and the Rapid Polymyxin NP Test were able to detect heteroresistant isolates (n = 2). Thus, there is an urgent need to further optimize the diagnosis strategies for colistin resistance.

Characterization of Carbapenemase-Producing Klebsiella pneumoniae Isolates from Two Romanian Hospitals Co-Presenting Resistance and Heteroresistance to Colistin.

Klebsiella pneumoniae is a notorious human pathogen involved in healthcare-associated infections. The worldwide expansion of infections induced by colistin-resistant and carbapenemase-producing Enterobacterales (CPE) isolates has been increasingly reported. This study aims to analyze the phenotypic and molecular profiles of 10 colistin-resistant (CR) isolates and 2 pairs of colistin-heteroresistant (ChR) (parental and the corresponding resistant mutants) isolates of K. pneumoniae CPE sourced from two hospitals. The phenotypes of strains in the selected collection had been previously characterized. Antimicrobial susceptibility testing was performed using a Vitek 2 Compact system (BioMérieux SA, Marcy l'Etoile, France), the disc diffusion method, and broth microdilution (BMD) for colistin. Whole-genome sequencing (WGS) did not uncover evidence of any mobile colistin resistance (mcr) genes, although the mgrB gene of seven isolates appeared to be disrupted by insertion sequences (ISKpn25 or ISKpn26). Possible deleterious missense mutations were found in phoP (L4F), phoQ (Q426L, L26Q, L224Q, Q317K), pmrB (R256G, P95L, T157P, V352E), and crrB (P151S) genes. The identified isolates belonged to the following clonal lineages: ST101 (n = 6), ST147 (n = 5), ST258 (n = 2), and ST307 (n = 1). All strains harbored IncF plasmids. OXA-48 producers carried IncL and IncR plasmids, while one blaNDM-1 genome was found to harbor IncC plasmids. Ceftazidime-avibactam remains a therapeutic option for KPC-2 and OXA-48 producers. Resistance to meropenem-vaborbactam has emerged in some blakPC-2-carrying isolates. Our study demonstrates that the results of WGS can provide essential evidence for the surveillance of antimicrobial resistance.

[Antimicrobial use and its correlations with the frequency of carbapenem-resistant Pseudomonas aeruginosa strains in a hospital setting]. / Evaluarea consumului de antibiotice si a efectului acestuia asupra frecventei tulpinilor de Pseudomonas aeruginosa carbapenem rezistente în mediul spitalicesc.

One of the major causes leading to increased antibiotic resistance is excess antimicrobial consumption. We have analysed the correlation between antibiotic use and frequency of carbapenem-resistant Pseudomonas aeruginosa (CRPA) strains in the general intensive care unit of a university hospital Antibiotic use was expressed as number DDD (daily defined doses)/100 occupied hospital bed-days (BD). CRPA incidence rates were determined by number of unique isolates reported to 100,000 BD. The average use of antibiotics between January and August 2008 was 174 DDD/100 BD. The first four most frequently prescribed antibiotics were as follows: first and second generation cephalosporins (47 DDD/100 BD), carbapenemns (29 DDD/100 BD), fluoroquinolones (26 DDD/100 BD) and glycopeptids (20 DDD/100 BD). Average monthly incidence rate of CRPA was 546/100,000 BD (319-773/100,000 BD. CI 95%). There was a correlation between CRPA incidence rate and carbapenem plus fluoroquinolone use (Pearson coefficient of correlation r = 0.7, p < 0.05). Our data showed that the evolution of CRPA incidence rates was related to carbapenem and fluoroquinolone use.