Occurrence of antibiotic-resistant human pathogens in integrated fish farms

The occurrence of antibiotic-resistant human pathogenic bacteria in integrated fish farms was studied in a Southeast Asian country. A total of 9 fish ponds were sampled for Salmonella, Vibrio, Aeromonas and Plesiomonas. Salmonella species were present in 28% of samples of fish, pond sediment and pond water, A.hydrophila in 67% of samples of fish, P.shigelloides in 22% of samples of fish and V.parahaemolyticus in 11% of the samples of fish, sediment and water. V.cholerae was not found in any of the samples of fish, pond sediment or pond water. Results showed that significant levels of antibiotic-resistant human pathogenic bacteria occur in aquaculture ponds where antibiotics are routinely incorporated into animal feeds. Antibiotic-resistant strains of Salmonella, A.hydrophila and P.shigelloides were isolated from fish samples. Of the 118 microorganisms isolated and tested during the study, 11% were resistant to nalidixic acid, 12% to oxolinic acid, 17% to chloramphenicol, 6% to neomycin, 74% to oxytetracycline, 75% to tetracycline, 47% to furazolidone and 25% to sulphamethoxazole combined with trimethoprim. Plasmids were detected in a strain of Salmonella, other members of the Enterobacteriaceae and several Pseudomonas species. Health risks and implications associated with these findings are discussed.