Distribution of blaOXA genes among carbapenem-resistant Acinetobacter baumannii nosocomial strains in Poland.

Acinetobacter baumannii is an important nosocomial pathogen occurring particularly in intensive care (ICU) as well as burn therapy units (BTU). A. baumannii strains have emerged as resistant to almost all antimicrobial agents, including carbapenems. b-lactamase-mediated resistance is the most common mechanism for carbapenem resistance in this species. Carbapenem-hydrolysing class D b-lactamases - OXA are widespread among A. baumannii strains. It is suggested that ISAba1 plays an important role in drug resistance. The aims of the study were detection of OXA encoding genes and presence of ISAba1. The study included the total of 104 isolates of carbapenem-resistant A. baumannii, obtained from patients hospitalized in ICU and BTU of Specialized Hospital in Krakow. Multiplex PCR was applied for detection of selected OXA carbapenemases encoding genes. PCR analysis showed the presence of bla OXA-51-like gene and ISAba1 in all isolates. 46 strains carried bla OXA-51-like and bla OXA-23-like genes while 48 bla OXA-51-like and bla OXA-40-like genes. 3 isolates carried: bla OXA-51-like , bla OXA-23-like and bla OXA-40-like genes. 7 strains encoded an OXA-51-like carbapenemase but were negative for enzymes belonging to the other families tested. Comparative analysis of ICU and BTU isolates revealed the dominance of: bla OXA-51-like and bla OXA-40-like among ICU while bla OXA-51-like and bla OXA-23-like in BTU.