Molecular characterisation and antimicrobial resistance of Vibrio vulnificus and Vibrio alginolyticus isolated from mussels (Mytilus galloprovincialis)

Twelve Vibrio vulnificus biotype 1 and 11 Vibrio alginolyticus isolated from mussels in Italy were analysed by antimicrobial resistance, plasmid profiles, random amplification of polymorphic DNA (RAPD), and single enzyme amplified fragment length polymorphism (sAFLP). Plasmid DNA was detected in three V. vulnificus and four V. alginolyticus cultures. All isolates were resistant to at least two antimicrobial agents: all isolates were resistant to ampicillin, carbenicillin and streptomycin, except one V. alginolyticus which was sensitive to carbenicillin and two V. alginolyticus which were sensitive to streptomycin. No association was detected between the presence of plasmid DNA and antimicrobial resistance. Seven of the twelve V. vulnificus and two of the eleven V. alginolyticus cultures were susceptible to the 10 microg of the vibriostatic compound O/129; all cultures were susceptible to the 150 microg of O/129. Both RAPD and sAFLP was found to be reproducible. Ten sAFLP and seven RAPD profiles were detected amongst the 12 V. vulnificus cultures: three cultures were identified as indistinguishable by both methods. RAPD and sAFLP analysis of V. alginolyticus generated nine and seven profiles respectively, and these two methods were independent. These results demonstrate extreme variability of V. vulnificus and V. alginolyticus isolated from mussels, and both RAPD and sAFLP provided information on intraspecific differences which will be useful for molecular epidemiological or ecological studies. A combination of methods gave optimal discrimination, although a single method could provide sufficient information to characterise V. vulnificus isolates.