Prevalence of a New Variant OXA-204 and OXA-48 Carbapenemases Plasmids Encoded in Klebsiella Pneumoniae Clinical Isolates in Tunisia

Carbapenemase-producing Klebsiella pneumoniae strains have emerged as a major problem for healthcare systems. The aim of this study was to determine the role and diversity of plasmids harboring carbapenemases encoding genes from a collection of K. pneumoniae isolates recovered between July 2011 and January 2012, with decreased susceptibility to carbapenems. Imipenem (IPM), ertapenem (ETP), meropenem (MEM), and doripenem (DOR) minimum inhibitory concentrations (MICs) were determined by E-test. Carbapenemase production was detected with the modified Hodge test. β-Lactamases encoding genes were amplified by PCR and sequenced. Plasmid incompatibility groups harbored by carbapenemases producers were investigated using the PCR-based replicon typing method and the clonal relationship of the isolates was investigated by pulse filed electrophoresis. IMP, ertapenem, meropenem, and doripenem MICs ranged between 0.25 and 16 mg/L. Carbapenemase activity was detected in 14 isolates. Two carbapenemases were identified: OXA-48 in 13 isolates and a new variant OXA-204 in 1 isolate, in combination with extended-spectrum β-lactamases, CTX-M-1, CTX-M-9, CTX-M-14, CTX-M-15, and VEB-8. One isolate produced CMY-2. OXA-48 and the new variant OXA-204 were confirmed as transferable plasmid encoded. The carbapenemase-producing K. pneumoniae harbored plasmids of the A/C, LVPK, and L/M replicon types. Thirteen different pulso types were observed. Three pairs of isolates showed a clonal relatedness. This diversity in β-lactamases, in pulso types and in plasmid content, shows the ability of OXA-type carbapenemase to disseminate. This is worrying for the control of the increase in antibiotic resistance frequency and necessitates that continuous investigations in the clinical setting remain a high priority to clarify the contribution of antimicrobial use into multiresistance bacterial dissemination.