The genus Aeromonas: biochemical characteristics, atypical reactions, and phenotypic identification schemes

Abstract

A total of 193 strains representing 14 different Aeromonas genomospecies were evaluated for 63 phenotypic properties to create useful tables for the reference identification of mesophilic aeromonads. Only 9 of 62 biochemical tests (14%) yielded uniform results, and the fermentation of certain carbohydrates was found to be linked to specific species. A number of unusual or aberrant properties for the genus Aeromonas were also detected in the collection of 428 strains (193 in the phenotypic study, 235 in a retrospective review). These tests included susceptibility to the vibriostatic agent, fermentation of m-inositol and D-xylose, hydrolysis of urea, and the lack of cytochrome oxidase activity. Fermentation of melibiose was linked to raffinose fermentation in all Aeromonas species except A. jandaei. Keys are provided for clinical laboratories choosing to identify aeromonads to species level based upon initial Møeller decarboxylase and dihydrolase reactions. In addition, several new tests were identified that help to separate members of the A. caviae complex (A. caviae, A. media, and A. eucreonophila).

FIG. 1.

Use of Møeller decarboxylase and dihydrolase reactions as a screening tool for recognition of potential species giving the indicated reaction. *, only rare strains of these species display this pattern. Abbreviations: LDC, lysine decarboxylase; ODC, ornithine decarboxylase; ADH, arginine dihydrolase; V, variable.