Antibiotic resistance and plasmid profile of environmental isolates of Vibrio species from Mai Po Nature Reserve, Hong Kong.

In this study, three environmental isolates of Vibrio species were isolated from water and sediment samples of Mai Po Nature Reserve, Hong Kong SAR. They were identified to be Vibrio cholerae MP-1, Vibrio aestuarianus MP-2 and Vibrio vulnificus MP-3 by both biochemical test and subsequent full-length 16S rDNA sequencing. Both disc diffusion susceptibility test and microplate dilution technique were used to investigate the antibiotic resistance profile of these three bacteria. Results from both assays were in generally good agreement. All three isolates were strongly resistant to beta-lactam family of antibiotics while susceptible to tetracycline, chloramphenicol, nalidixic acid and streptomycin. In addition, V. cholerae MP-1 was very tolerant to high concentration of vibriostatic agent O/129 to 40 microg/ml, at which the growth of V. aestuarianus MP-2 and V. vulnificus MP-2 was completely inhibited. A small naturally occurring plasmid was found in V. cholerae MP-1 while no plasmid was detected in the other two bacteria. This study suggests that Mai Po Nature Reserve harbors bacteria of unique characteristics that warrant further investigation.