Assessment of carbapenem resistance and presence of acquired carbapenemases in Russian nosocomial isolates of Acinetobacter spp.

Abstract number: P1505

Martinovich A., Shevchenko O., Edelstein M., Kozlov R.

Objectives: To determine resistance rates to imipenem (IPM) and meropenem (MER) and occurrence of acquired metallo-b-lactamases (MBLs) and class D (OXA) carbapenemases in nosocomial Acinetobacter spp. from Russian ICUs.

Materials and Methods: A total of 464 consecutive nosocomial isolates collected as part of the national surveillance study RESORT in 30 ICUs of 20 Russian cities in 2002–2004 were studied. The susceptibilities to IPM and MER were determined by agar dilution method and interpreted according to CLSI guidelines. A double-disk synergy test with EDTA was used for phenotypic detection of MBL production. The presence of the genes for VIM- and IMP-type MBLs and the genes for acquired class D carbapenemases of three groups: OXA-23-like, OXA-40-like and OXA-58, was examined by PCR.

Results: A total of 11(2.4%) and 17(3.7%) were nonsusceptible to IPM (MIC range: 8–128 mg/ml) and MER (MIC range: 8–64 mg/ml), respectively. MBL production was not detected among carbapenem-nonsusceptible isolates by either phenotypic or molecular tests. The genes for acquired OXA-type carbapenemases were found in 11 (2.4%) isolates of A. baumannii exhibiting variable MICs of IPM (4–32 mg/ml) and MER (8–32 mg/ml). Eight of these isolates from two hospitals of Moscow and Novosibirsk harboured the genes for OXA-58 and the remaining three isolates from Moscow and Irkutsk carried the genes for OXA-23-like enzymes. No acquired carbapenemase genes were detected in the other six isolates exhibiting increased resistance to IPM or MER (MICs: 8–128 mg/ml).

Conclusions: Resistance to carbapenems remains rare among nosocomial Acinetobacters in Russia. However, the identification of acquired OXA-type carbapenemases in isolates from geographically distant regions of Russia poses the risk of future dissemination of resistance.