GENOTYPIC AND PHENOTYPIC DIVERSITY IN ACINETOBACTER BAUMANNII ISOLATES FROM DIFFERENT SOURCES

Objectives: Acinetobacter baumannii is an opportunistic pathogen responsible for outbreaks of infection worldwide. Contrary to other species of its genus, it is almost exclusively found in the nosocomial environment, and external reservoirs of infection have not been identified. In addition, although some studies have isolated strains from non-clinical sources, the diversity between A. baumannii from clinical and non-clinical sources is unknown. We compared the genotypic and phenotypic diversity of A. baumannii strains isolated from non-human sources, in order to understand the intra-species diversity and to gain clues on how A. baumannii adapted to become a successful human pathogen. Methods: Sequence group typing of a collection of A. baumannii strains from non-human sources (veterinary, soil, water, food-associated) was performed by PCR amplification and genotypic diversity was determined by RAPD-DAF4 analysis. Strain growth was tested on Acinetobacter isolation agar and in liquid culture media at temperatures from 18-44°C. Resistance to antimicrobial agents and heavy metals was tested by the agar-dilution methods. Biofilm formation on polystyrene plates and resistance to desiccation on nitrocellulose membranes were also determined. Culture supernatants were assayed for iron-chelating, haemolytic, phospholipase C and proteolytic activities. Hydrolysis of polysaccharides was tested on agar plates supplemented with different substrates. Results: A. baumannii isolates were divided into different genotypes, some of which corresponding to the three International clonal lineages. Phenotypic assays demonstrated considerable intra-specific diversity. All strains to grew at temperatures ranging from 18-37°C, and had the ability to form biofilm and to produce a number of exoproducts with enzymatic activity, although to a different extent. Differences were observed between veterinary and environmental strains, with veterinary isolates showing higher antibiotic resistance and exoproduct production. Several environmental isolates were unable to grow on Acinetobacter isolation media. Conclusion: A. baumannii strains isolated from different origins show genotypic and phenotypic diversity, suggesting that different A. baumannii populations might have emerged as a result of adaptation to different habitats. Keywords: adaptation, environment, diversity, exoenzyme, habitat, phenotype Topic: Taxonomy, Population Genetics, Evolution and Comparative Genomic