First Report of the Escherichia coli Co-Producing CTX-M-15 ESBL and VIM-4 MBL in Russia

Background: In this study, we describe a resistance phenotype and b-lactamase context of the E. coli strain 55/1389 with decreased susceptibility to carbapenems that was isolated from a 26-year old female neurosurgery ICU patient with catheter-associated UTI in November 2006 in Moscow. Methods: Susceptibility testing was performed by agar dilution method according to CLSI guidelines. Double-disk synergy tests with clavulanic acid and EDTA were used for detection of ESBL and MBL phenotypes, respectively. Transferability of b-lactam resistance was tested in mating experiments with the E. coli AB1456, Rif recipient. The b-lactamase genes and their environments were identified by PCR, PCR-mapping, and sequencing. Results: The E. coli 55/1389 exhibited high-level resistance to ampicillin, piperacillin, piperacillin-tazobactam, cefotaxime, ceftazidime, cefepime, cefoxitin, aztreonam (MICs, >=256 mg/L) and border-line susceptibility to imipenem and ertapenem (MICs, 2 and 4 mg/L). It was also resistant to all non-b-lactam agents tested: ciprofloxacin, gentamicin, amikacin, netilmicin, and co-trimoxasole, except fosfomycin. Phenotypic tests for ESBL and MBL were positive.PCR and sequencing identified the presence of ISEcp1 element upstream of the blaCTX-M-15 gene and a class 1 integron with the blaVIM-4 gene cassette in the first position. No transfer of these resistance determinants to the recipient strain was observed. Conclusions: To our knowledge, this is the first report of the co-production of ESBL and MBL in a clinical strain of Enterobacteriaceae in Russia. While CTX-M-15 is the most common ESBL found in Russian E. coli strains, the production of VIM-4 MBL has never been reported in any species in Russia.