Phenotypic characteristics of human clinical and environmental Aeromonas in Western Australia

Aim: To determine the phenotypic characteristics of 199 Aeromonas strains comprising 146 clinical and 53 environmental isolates. Methods: Identification was based on a scheme consisting of 62 biochemical tests including two novel tests introduced as potential phenotypic markers. Results: One hundred and eighty-five strains (93%) were identified to species level while eight (4%) resembled members of the Aeromonas hydrophila complex and six (3%) could not be assigned to any taxon. There were no significant phenotypic differences between clinical and environmental strains of the three most commonly isolated species A. hydrophila, Aeromonas veronii subspecies sobria and Aeromonas caviae. The most frequently isolated species in human clinical material and environmental samples was A. hydrophila (54.8% and 45.3%, respectively). Conclusions: Phenotypical identification showed that A. hydrophila was the most frequently isolated Aeromonas from clinical and water samples. The introduction of novel tests did not improve the discriminatory power of the scheme and the lack of definitive phenotypical markers continues to hinder Aeromonas taxonomy.