Meropenem heteroresistance in clinical isolates of OXA-48–producing Klebsiella pneumoniae

Abstract

OXA-48-producing Klebsiella pneumoniae isolates often show growth of colonies within inhibition zones in carbapenem diffusion assays. The nature of these colonies was investigated in a series of clinical isolates of OXA-48producing K. pneumoniae obtained in the context of a hospital outbreak, and they were found to be persistent colonies that reproduced again the same phenotype when they were collected and tested in diffusion assays again. The frequency of mutations conferring resistance to meropenem (8 μg/mL) was determined for the same isolates. The average mutation frequency was 5.47·10 −6 (range: 2.59·10 −8 -5.87·10 −5 ), and the analysis of several resistant mutants showed that all of them had mutations in the ompK36 porin gene. Heteroresistance was investigated using population analysis profiling. The profiles were compatible with mutation frequency assays, and all the colonies analyzed were resistant mutants. In OXA-48-producing K. pneumoniae, the growth of persisters seems to be specific of diffusion assays.

Comparative Activities of Ceftazidime-Avibactam and Ceftolozane-Tazobactam against Enterobacteriaceae Isolates Producing Extended-Spectrum β-Lactamases from U.S. Hospitals

“…The ceftolozane-tazobactam resistance mechanisms in ESBL-producing isolates are not well understood. Outer membrane sequence alterations that could play a role in resistance to ceftolozane-tazobactam were not observed among resistant K. pneumoniae, E. coli, and E. cloacae isolates compared to those in genetically similar isolates susceptible to this combination; however, decreased expression of OMP-encoding genes or posttranslational modifications that could play a role in resistance to ␤-lactams (22)(23)(24) were not evaluated and present a limitation of this study. Additionally, efflux extrusion of the antimicrobial or the inhibitor and overexpression of ␤-lactamases could also be important in resistance to ceftolozane-tazobactam.…”

Performance of the BD Phoenix CPO detect assay for the detection and classification of OXA-48 producing-Escherichia colithat do not coproduce ESBL/pAmpC

“…coli , rates of carbapenem-heteroresistance of 25-32%, detected by disk-diffusion, have been described (24, 25). Furthermore, for OXA-48, presence of colonies within the inhibition zones in disk or gradient diffusion assays for meropenem, independently of the MIC values measured by microdilution, has been reported in Klebsiella pneumoniae producing this carbapenemase (26). Previous studies have shown that the outcomes of in vitro susceptibility testing of tigecycline can be affected by the testing method used, mainly in Acinetobacter baumannii but also for carbapenemase-producing enterobacterales (27).…”

Antibiotic Heteroresistance in Klebsiella pneumoniae

“…When third-generation cephalosporins were introduced into clinical use, this difference explains why K. pneumoniae isolates were initially more sensitive to these antibiotics than E. coli strains [ 78 ]. Porin deficiency reduces the uptake of β-lactams and, in combination with ESBLs activity, may confer clinical resistance [ 40 , 62 , 79 ]. The emergence of imipenem-resistant subpopulations with decreased levels of OmpK36 was reported by Adams-Sapper et al ( Table 1 ).…”