Acinetobacter calcoaceticus-A. baumannii complex: isolation, identification and characterisation of environmental and clinical strains

Abstract

Bacteria from Acinetobacter calcoaceticus-A. baumannii (Acb) complex are widespread, multi-drug resistant bacteria of great clinical importance. The aim of this study was to determine the most suitable sole carbon source for their isolation/cultivation from environmental samples, to facilitate easier isolation and to compare the properties of environmental strains and wound isolates, in order to reveal whether environmental isolates are a reservoir of infection. In addition to acetate, which is used in routine procedures, the most appropriate carbon sources for isolation, were alanine, L-histidine and L-tyrosine. Because none of the substrates enabled isolation from all samples, new carbon sources or their combinations should be further considered. In subculture, L-tyrosine, alanine, L-histidine and pyruvate were the most appropriate for bacterial growth. Environmental and clinical strains were identified using classical methods and multiplex PCR, and out of 31 strains two were not identified as A. baumannii, but as other members of the Acb complex (13 UT group). All strains possessed integron class 1, while all environmental isolates and one clinical strain possessed integron class 2. Integron class 2 should be further examined as a marker for environmental strains. The environmental strains were multi-drug resistant and there was no statistical difference in antibiotic resistance in comparison to clinical strains (p = 0.36). The detected similarity of RAPD-PCR fingerprints among A. baumannii environmental and wound isolates, suggests their epidemiological relatedness, raising the urgency for finding adequate solutions for prevention of further resistance dissemination among strains of different origins.