Emergence and spread of carbapenem-resistant strains of Acinetobacter baumannii in a tertiary-care hospital in Poland

This study analysed the occurrence of carbapenem resistance among Acinetobacter baumannii isolates from a tertiary-care hospital in Poland, together with the molecular epidemiology of these isolates and the risk-factors for their acquisition and possible nosocomial spread. The medical charts of 21 patients with Acinetobacter infection or colonisation revealed that A. baumannii isolates were obtained most frequently from intensive care unit and surgical patients (particularly those receiving transplantation surgery). First isolation occurred, on average, on day 21 following admission (range 5-45 days). Infection with Acinetobacter contributed directly to the death of seven patients. Several patients were infected with more than one strain, and molecular typing revealed the co-circulation of three predominant clones, of which two belonged to the Acinetobacter lineages designated as European clones I and II. All three clones encoded an OXA-51-type carbapenemase, but were negative for carbapenemases belonging to the OXA-23, OXA-24 and OXA-58 families. The OXA-51 gene was found in both resistant and susceptible isolates, and was not associated directly with carbapenem resistance. Etests with imipenem and imipenem plus EDTA indicated production of a metallo-beta-lactamase (MBL) in carbapenem-resistant isolates. PCRs for IMP-type MBLs were negative, but PCR using consensus primers for VIM-type MBLs were positive for carbapenem-resistant isolates belonging to the European clone II lineage. The occurrence of a VIM-type MBL in association with one of the epidemic lineages of A. baumannii is a cause for concern. Further studies are needed to evaluate possible inter-hospital spread of resistant A. baumannii strains in Poland.