Detection of R factors in naturally occurring Vibrio anguillarum strains

R factors were detected in Vibrio anguillarum strains from vibrio-diseased freshwater fish, ayu (Plecoglossus altivelis), in Japan. It was found that 65 out of the 68 random isolates from epidemics of vibrio disease in 1973 carried transferable drug resistance factors. The most common type determined resistance to sulfonamides, streptomycin, chloramphenicol, and tetracycline and belong to the fi(-) type. The high incidence of R factors in Vibrio anguillarum from cultured fish is assumed to be due to selective pressure exerted by chemotherapeutic agents used in fish culturing.