Cytotoxicity and Antibiotic Resistance Profiles of Aeromonas hydrophila Isolates From a Broiler Processing Operation

The cytotoxicity and antibiotic resistance profiles of Aeromonas hydrophila isolates recovered from broiler carcasses and chill water samples taken from a Georgia processing plant were determined. Carcasses were sampled at pre- and post-evisceration locations, immediately after immersion chilling, and after being boxed, iced and refrigerated for 48 h. Grab samples of chill water were randomly selected for A. hydrophila recovery. Resistance of isolates to nine antibiotics was determined with the Bauer disc diffusion method (i.e., to ampicillin, cephalothin, streptomycin, kanamycin, chloramphenicol, naladixic acid, tetracycline, neomycin, and gentamicin). Multiple antibiotic resistance occurred in 46.2% of 119 isolates. The majority of the multiple antibiotic-resistant isolates (76.4%) were resistant only to ampicillin and cephalothin. The remaining multiple antibiotic-resistant isolates (23.6%) were resistant to various combinations of 2, 3, or 4 antibiotics, most of which were recovered from carcasses immediately after evisceration. Cytotoxin activity was detected in 63.8% of all isolates using the Y-1 mouse adrenal tumor cell line. Cytotoxin positive isolates were recovered from all sampling locations including chill water. The highest cytotoxicity titers were shown among isolates recovered from carcasses immediately after evisceration. These data suggest bird fecal contamination as an important source of A. hydrophila in broilers and broiler processing plants rather than environmental contamination.