Prevalence and characteristics of Aeromonas species isolated from processed channel catfish

From August 1994 to May 1995, 238 channel catfish fillets collected from three processing plants in the Mississippi Delta at four time periods were tested for the presence of Aeromonas species. Identification of Aeromonas spp. was accomplished using an automated Vitek bioassay system with gram-negative and nonfermenter cards. Approximately 36.1% were positive for A. hydrophila, 35.7% for A. sobria, and 10.9% for A. caviae. All three Aeromonas spp. were found in all three processing plants, and the incidence of A. hydrophila contamination appeared to be higher in summer than other seasons. Eighty-six percent of the Aeromonas isolates were hemolytic on 5% sheep blood agar plates. Most isolates were susceptible to chloramphenicol, neomycin, streptomycin, and trimethoprim-sulfamethoxazole and resistant to ampicillin and bacitracin. Results suggest that Aeromonas spp. are prevalent in processed channel catfish, and most isolates are hemolytic and resistant to ampicillin and bacitracin.