Transmission of the R factor by conjugation from a naturally-isolated, multiple drug-resistant strain of Vibrio eltor to Shigella and Salmonella

A transferable multiple drug resistance plasmid from Vibrio cholerae O1

Ten multiple antimicrobial-resistant isolates of Vibrio cholerae O1 isolated from patients in Uganda were characterized, and the transferability of resistance to bacteria of diverse origins was investigated. The isolates were toxigenic and belonged to biotype E1 Tor, serotype Ogawa, and ribotype 8, and possessed a 130-MDa plasmid of incompatibility group 6-C. This plasmid, designated pRVC1, was shown to confer resistance to trimethoprim (mediated by a dhfrI gene), sulfonamides (a suII gene), tetracycline [a tet(C) gene], chloramphenicol (a catI gene), ampicillin (a beta-lactamase gene other than blaTEM or blaSHV), and streptomycin. pRVC1 proved to be transmissible at frequencies between 1 x 10(-1) and 5 x 10(-6) transconjugants per recipient to a variety of bacterial pathogens, including those of humans, animals, and fish. Most efficient transfer was observed from V. cholerae to strains of Shigella flexneri, Escherichia coli, Vibrio parahaemolyticus, and three Aeromonas species. The present in vitro study suggests that pRVC1 may spread from V. cholerae to other bacteria pathogenic to man, animals, and fish in natural environments.

Antibiotic resistance patterns of Vibrio mimicus isolated from human and environmental sources in Bangladesh

Twenty-five environmental and 19 clinical strains of Vibrio mimicus were tested for antibiotic susceptibility patterns. Environmental strains were resistant to streptomycin, kanamycin, and trimethoprim-sulfamethoxazole; clinical strains were susceptible. Environmental strains showed variable resistance to ampicillin (44%), but clinical strains were susceptible. All strains tested were susceptible to chloramphenicol and gentamicin.