Comparison of seven selective media for the isolation of mesophilic Aeromonas species in fish and meat.

Seven selective agar media and two enrichment broths were evaluated for their suitability for the isolation of mesophilic Aeromonas species from meat, fish, and shellfish samples. In a first trial, aeromonads were inoculated in fish and meat samples and reisolated using all selected media. For qualitative isolation, enrichment in alkaline peptone water (pH 8.7 +/- 0.1) at 28 degrees C and subsequent plating onto sheep blood agar supplemented with 30 mg/L ampicillin (ASBA 30) and bile salts-irgasan-brilliant green agar (BIBG) at 35 degrees C led to the best results. For quantitative assays, direct plating on the same agar media is recommended. In a second trial, 829 meat, fish, and shellfish samples were investigated with the same methods. The results show that BIBG is the most selective medium and that presumptive identification of aeromonads on ASBA 30 is very easy. Finally, we could confirm the opinion of other workers that optimal recovery of mesophilic Aeromonas spp. requires the use of more than one agar medium.