Heteroresistance to Colistin in Clinical Isolates of Klebsiella pneumoniae Producing OXA-48

Heteroresistance to colistin can be defined as the presence of resistant subpopulations in an isolate that is susceptible this antibiotic. Colistin resistance Gram-negative bacteria more frequently related chromosomal mutations and insertions. This work aimed study heteroresistance nine clinical isolates Klebsiella pneumoniae producing OXA-48 describe genomic changes mutants with acquired vitro. Antimicrobial susceptibility was determined by broth microdilution (BMD) population analysis profiling (PAP). The proteins were analyzed for mutations. Additionally, PCR mgrB gene performed identify In parental isolates, PAP method showed colonies growing on plates concentrations up 64 mg/L, corresponding stable mutant subpopulations. MICs some from plate containing 4×MIC had absolute values ≤2 mg/L higher than persistent variants. identified insertion sequence inactivated 21 mutants. Other substitutions investigated found PhoP, PhoQ, PmrB, PmrC, CrrA CrrB proteins. K. attributed mainly insertions point results will improve understanding regarding mechanisms OXA-48.