Molecular epidemiology of NDM-1-and OXA-48-producing Klebsiella pneumoniae in an Iranian hospital: clonal dissemination of ST11 and ST893

Objectives: Despite the fact that the bla(OXA-48) and bla(NDM-1) genes have successfully disseminated among Klebsiella pneumoniae isolates worldwide, outbreaks remain unidentified in Iran. Here we examined the molecular epidemiology of 96 carbapenem-resistant K. pneumoniae recovered from an Iranian hospital. Methods: A total of 96 non-replicate carbapenem-resistant K. pneumoniae were recovered from clinical specimens in a university hospital. Detection of ESBLs and carbapenemases produced by studied strains was performed using PCR and DNA sequencing. The bacterial isolates were assigned to clonal lineages by PFGE and MLST. In addition, plasmids were analysed by PCR-based replicon typing and conjugation assays. Results: All isolates harboured bla(OXA-48) and bla(NDM-1) genes together or alone. Almost all strains also carried ESBL genes. Eighty-seven isolates of K. pneumoniae were categorized into seven pulsotypes. The predominant strain clusters/pulsotypes associated with the outbreak corresponded to ST11 (48/96) and ST893 (31/96). Plasmids carrying bla(OXA-48) and bla(NDM-1) were successfully transferred to Escherichia coli K12 as the recipient strain. bla(OXA-48) was located on IncL/M plasmids of similar to 39 kb, while bla(NDM-1) was carried by either an IncFII plasmid of similar to 50 kb or an untypeable plasmid of similar to 4 or 10 kb. Conclusions: We describe two separate outbreaks of bla(OXA-48)- and bla(NDM-1)-carrying K. pneumoniae strains associated with dissemination of the ST11 and ST893 clones, with the ICU acting as the epicentre. The spread of plasmids carrying carbapenemase genes resulting in fulminant antimicrobial resistance is a severe concern.