Selective enrichment broth for the isolation of Aeromonas sp. from chicken meat

Six selective agents (ampicillin, novobiocin, cephalothin, bile salts, brilliant green and ethanol) were tested during the development of a selective enrichment broth for the isolation of Aeromonas sp. from food. Cephalothin at 10 mg/l was found to be the best selective agent owing to its greater selectivity and efficiency in recovering stressed and lower cell concentrations of Aeromonas sp. Higher concentrations (15-25 mg/l) of cephalothin were inhibitory to some strains of A. sobria. Cephalothin (10 mg/l) was incorporated in buffered dextrin broth (BCDB-10) and alkaline peptone water (CAPW-10) and employed for the isolation of Aeromonas sp. from chicken meat naturally and artificially inoculated (with 10(9) cells/ml of A. hydrophila). The highest isolation rate (22%) with naturally contaminated chicken was achieved with CAPW-10 in comparison to 16% with BCDB-10 and 8% with APW. Similarly, from artificially inoculated samples, 100% isolation was accomplished with CAPW-10, against 80% with BCDB-10 and 50% with APW.