Abstract
BACKGROUND: Vibrio cholerae is an important bacterium causing profuse watery diarrhea. Cholera had swept the whole Shandong province from 1975 to 2013. METHODS: From epidemiological data and pulsed-field gel electrophoresis data, we selected 86 V. cholerae isolates appearing in Shandong Province in China from 1975 to 2013 and characterized them by multilocus sequence typing (MLST)/multi-virulence locus sequence typing (MVLST), antibiogram and analysis of genes related to antibiotic resistance. RESULTS: Combined MLST/MVLST data revealed 33 sequence types and a major group. Within the group, 3 subgroups (ST1, ST24 and ST29) were revealed, prevalent in the strains isolated during the 1980s, 1990s and 21st century, respectively. All the O1 isolates after 1990 were found to be El Tor variants harboring the classical ctxB gene. The tcpA gene of O139 strains had a mutation at amino acid position 62 (N→D). Antibiotic resistance of V. cholerae increased over time. Most El Tor variants between 1998 and 1999 were resistant to trimethoprim/sulfamethoxazole. The O139 strain, since its appearance in 1997, had significantly broader spectrum of antibiotic resistance than O1 variants. The presence of the SXT element corresponds to the trend of growing drug resistance. CONCLUSION: The analysis of genotypic polymorphism and enhanced resistance of V. cholerae indicated continuous variation and evolution of this pathogenic agent in Shandong Province.