Biochemical identification and numerical taxonomy of Aeromonas spp. isolated from environmental and clinical samples in Spain

Abstract

<b>Aims:</b> To study the phenotypic characteristics of <i>Aeromonas</i> spp. from environmental and clinical samples in Spain and to cluster these strains by numerical taxonomy. <b>Methods and Results:</b> A collection of 202 <i>Aeromonas</i> strains isolated from bivalve molluscs, water and clinical samples was tested for 64 phenotypic properties; 91% of these isolates were identified at species level. <i>Aeromonas caviae</i> was predominant in bivalve molluscs and <i>Aerom. bestiarum</i> in freshwater samples. Cluster analyses revealed eight different phena: three containing more than one DNA-DNA hybridization group but including strains that belong to the same phenospecies complex (<i>Aerom. hydrophila</i>, <i>Aerom. sobria</i> and <i>Aerom. caviae</i>), <i>Aerom. encheleia</i>, <i>Aerom. trota</i> and three containing unidentified <i>Aeromonas</i> strains isolated from bivalve molluscs. <b>Conclusions:</b> <i>Aeromonas</i> spp. are widely distributed in environmental and clinical sources. A selection of 16 of the phenotypical tests chosen allowed the identification of most isolates (91%), although some strains remain unidentified, mainly isolates from bivalve molluscs, suggesting the presence of new <i>Aeromonas</i> species. Numerical taxonomy was not in total concordance with the identification of the studied strains. <b>Significance and Impact of the Study:</b> Numerical taxonomy of <i>Aeromonas</i> strains isolated from different sources revealed the presence of potentially pathogenic <i>Aeromonas</i> spp., especially in bivalve molluscs, and phena with unidentified strains that suggest new <i>Aeromonas</i> species.