Epidemiology of Acinetobacter baumannii of animal origin

Acinetobacter baumannii is an opportunistic pathogen responsible for nosocomial infections, however the origins of these bacteria remain unclear. Sixteen A. baumannii strains collected from animals slaughtered for human consumption were investigated for their susceptibility profiles, resistance islands (RIs), class 1 integrons, insertion sequence ISAba1, and bla(OXA-51)-like and bla(AmpC) genes. Polymerase chain reaction (PCR) and sequencing approaches were used to identify and type the isolates using the intrinsic gene bla(OXA-51)-like genes. Genotyping was also performed by pulsed-field gel electrophoresis (PFGE) to establish whether there was a genetic relationship between animal isolates and the main human isolates of European clones I, II and III (ECI, ECII and ECIII) known to cause major hospital outbreaks. All 16 isolates (100%) were sensitive to carbapenems, gentamicin, ciprofloxacin and piperacillin/tazobactam but were resistant to amoxicillin, cefradine, trimethoprim and chloramphenicol. Moreover, all isolates had a baseline resistance to ceftazidime, with a minimum inhibitory concentration of 4 mg/L. All isolates lacked RIs, ISAba1 and class 1 integrons but harboured bla(OXA-51)-like and bla(AmpC) genes. In addition, this study reports for the first time three new bla(OXA-51)-like genes (bla(OXA-148), bla(OXA-149) and bla(OXA-150)) isolated from bacteria in cattle, which have not been found previously in human isolates. However, all isolates recovered from pig faecal samples harboured one type of bla(OXA-51)-like (bla(OXA-51) itself), which has already been reported in human clinical isolates. From sequencing of the bla(OXA-51)-like genes from animal isolates, it was possible to identify four different clusters similar to those identified by PFGE, which in turn also distinguished these four groups from the human ECI, ECII and ECIII strains.