Antibiotic resistance of Vibrio cholerae O1 El Tor strains from the seventh pandemic in China, 1961-2010

Antibiotic resistance is observed with increasing frequency among epidemic Vibrio cholerae strains in some countries. In this study, the antibiotic resistance profiles of V. cholerae O1 El Tor strains isolated in China from 1961 to 2010 were analysed. The frequency of antibiotic resistance among the seventh pandemic El Tor isolates from China remained low, except for resistance to nalidixic acid (45.9%), tetracycline (11%) and trimethoprim/sulfamethoxazole (38.5%). All test strains in the first multiyear epidemic in the 1960s were sensitive to all test antibiotics, whereas strains from the 1990s and later showed a rapid increase in the prevalence of resistance. The class I integron was present primarily among strains isolated between 1993 and 1998, and the prevalence of the SXT element was much greater among strains isolated after 1993. This study determined the regional resistance characteristics of epidemic clones in China and serves as a warning of the rapid dissemination of resistance in the past 20 years.