[The occurrence of antibiotic-resistant Aeromonas and Vibrio species in river water].

262 samples of river water had been analysed for the occurrence of antibiotic resistant Aeromonas and Vibrio strains. The bacteria were cultured on selective media containing the antimicrobial chemotherapeutic agents oxytetracycline, chloramphenicol, streptomycin, ampicillin, kanamycin, gentamycin or trimethoprim. Although it was not possible to identify antibiotic resistant bacteria of the genus Vibrio, resistant strains of Aeromonas hydrophila with a wide variety of resistance patterns could be cultured in many cases. R plasmids were found by means of conjugation in 21.2% of the 826 tested Aeromonas hydrophila strains. They were characterized with the aid of the fin- and pili test. The majority of the R plasmids were fin-negative, and the sex pili could be assigned strikingly often to sex pilus group C with the phages we used. 15 strains of Aeromonas hydrophila had been tested in agarose gel electrophoresis on plasmid DNA. In 11 Aeromonas hydrophila strains with transferable and in 3 from 4 strains with non transferable multiple antibiotic resistance plasmid DNA with 100 Megadalton had been found.