Colistin Resistance in KPC-2- and SHV-5-Producing Klebsiella pneumoniae Clinical Isolates in Bulgaria.

BACKGROUND/AIMS: Colistin resistance is increasingly recognized among carbapenemase-producing Klebsiella pneumoniae isolates in several European regions. The current study documents the appearance of colistin resistance among KPC-2 and SHV-5-produning K. pneumoniae strains in Bulgaria.

METHODS

Four colistin-resistant K. pneumoniae isolates were recovered from 2 patients hospitalized in the anesthesiology and resuscitation clinic of a tertiary care university hospital in Sofia, Bulgaria. Microbial identification and antimicrobial susceptibility testing was performed by Vitek 2 (Biomerieux, France). β-Lactamase genes were amplified using a panel of primers for detection of all MBL-types, KPCs, plasmid-mediated AmpCs in single PCR reactions, OXA-type carbapenemases, extended-spectrum β-lactamases (ESBLs) and TEM enzymes. The colistin-resistant mcr-1 gene was also investigated using previously described primers and conditions. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used to investigate clonality.

RESULTS

The 4 K. pneumoniae isolates exhibited colistin MICs >16 mg/L and showed multidrug-resistant phenotypes, remaining intermediately susceptible only to gentamicin. They were clustered into a single PFGE clonal type and MLST assigned them to sequence type 258. All isolates possessed KPC-2 carbapenemase and SHV-5 ESBL. They were negative for the plasmid-mediated colistin-resistant mcr-1 gene, possibly implying an intrinsic mechanism of resistance.

CONCLUSIONS

Although colistin use in Bulgaria only started moderately during 2014, the findings of the current study notify the appearance of colistin resistance among carbapenemase-producing Klebsiella species in another European region.