Analysis of Genes and Insertion Sequences Related to Carbapenem Resistance in Clinical Strains Isolated in Warsaw, Poland.

is an important cause of nosocomial infections worldwide. The elucidation of the carbapenem resistance mechanisms of hospital strains is necessary for the effective treatment and prevention of resistance gene transmission. The main mechanism of carbapenem resistance in is carbapenemases, whose expressions are affected by the presence of insertion sequences (ISs) upstream of genes. In this study, 61 imipenem-nonsusceptible isolates were characterized using phenotypic (drug-susceptibility profile using CarbaAcineto NP) and molecular methods. Pulsed field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) methods were utilized for the genotyping. The majority of isolates (59/61) carried one of the following acquired genes: (39/59), IS- (14/59) or IS- (6/59). Whole genome sequence analysis of 15 selected isolates identified the following intrinsic (OXA-51-like; = 15) and acquired class D β-lactamases (CHDLs): IS- (OXA-23-like; = 7), IS--IS (OXA-58-like; = 2) and (OXA-24-like; = 6). The isolates were classified into 21 pulsotypes using PFGE, and the representative 15 isolates were found to belong to sequence type ST2 of the Pasteur MLST scheme from the global IC2 clone. The Oxford MLST scheme revealed the diversity among these studied isolates, and identified five sequence types (ST195, ST208, ST208/ST1806, ST348 and ST425). CHDL-type carbapenemases and insertion elements upstream of the genes were found to be widespread among Polish clinical isolates, and this contributed to their carbapenem resistance.