Description
Aeromonas hydrophila (often referred as motile aeromonads) is a facultative anaerobe, which is characterized by growth at 37?C and motility. The detection of Aeromonas species in foods and environmental samples is usually quite easy. However, difficulties may arise when quantitative recovery is required or in cases where large number of other organisms are present. Kaper et al described a single tube medium for the rapid presumptive identification of A. hydrophila, which is also recommended by APHA. This single tube medium shows the following reactions: mannitol and inositol fermentation, ornithine decarboxylation and deamination, motility, indole and H2S production. The food samples should be processed as soon as possible upon arrival at the laboratory. Motile aeromonads are somewhat sensitive to pH values below 5.5; therefore, acidic foods should be processed soon after arrival in the laboratory. On the basis of biochemical characterization, Aeromonas can be differentiated as mannitol fermenters, inositol non-fermenters, absence of ornithine decarboxylase, and hydrogen sulfide not produced from thiosulphate. Usually in tubes containing Kapers Medium inoculated with A. hydrophila, the butts turn yellow due to acid formation and an alkaline band is formed at the top of the medium. Small amount of agar facilitates motility determination.
