Classification of Aeromonas spp. strains from human clinical material

Aeromonads are ubiquitous in aquatic environments and several species have been recognized as pathogens to a variety of animals including humans. The genus Aeromonas includes a tight group of species and subspecies, some of which have required reclassification. The present study was aimed on aeromonads isolated from human clinical material and classified by biotyping and ribotyping techniques. A group of 75 human aeromonads was identified on the complex level by biotyping as Aeromonas hydrophila complex and/or Aeromonas sobria complex. Identification to the species level was not reliable by biotyping and without additional techniques biotyping cannot be used to delineate closely related species of Aeromonas. Ribotyping clearly distinguished both complexes on the base of fragment lengths and furthermore in several cases enabled correct species identification. Aeromonas hydrophila complex yielded only long fragments in range 2 kbp to 20 kbp, while Aeromonas sobria complex showed also smaller fragments below 2 kbp. Aeromonas hydrophila subsp. hydrophila was predominant species in A. hydrophila complex and we did not prove the recently mentioned position of Aeromonas aquariorum as widely distributed species in clinical specimens and previously misidentified as A. hydrophila. Among A. sobria complex isolates the Aeromonas veronii bv. sobria strains were very frequent. Both taxa, A. hydrophila subsp. hydrophila and A. veronii bv. sobria showed great heterogeneity of ribotyping patterns in several clusters. Ribotyping results also proved occurrence of rare pathogens Aeromonas hydrophila subsp. dhakensis, Aeromonas bestiarum, Aeromonas jandaei, Aeromonas veronii bv. veronii and Aeromonas allosaccharophila in diarrheic stool samples. Species variability of aeromonads from clinical samples was not high and ribotyping was appeared as useful tool for reliable strain typing and species identification of aeromonads in combination with biotyping.