[Comparison of colonization ability of O1 and O139 Vibrio cholerae strains on soft-shelled turtle's surface].

Objective To study the preferred colonization sites of O1 Vibrio cholerae (V.cholerae) and the colonization ability difference for O1 and O139 V. cholerae on soft-shelled turtle's surface. Methods 8 O1 and O139 V. cholerae strains were obtained from branch of diarrheal diseases, Chinese center for disease control and prevention. 63 soft-shelled turtles weighing 150 g and 9 cm in length (diameter of calipash) were selected for use in the study. The preferred colonization sites and proliferation trend were studied by using bioluminescent imaging method. The colonization factors for O1 V. cholerae strains were studied by constructing colonization gene mutant strains (VC1897dmshA, VC1897dgbpA and VC1897dtcpA), performing competition colonization assays and analyzing the competitive indexes. After pairing off O1 and O139 strains respectively to perform 16 competition groups, the colonization difference of these two strains were studied by competition colonization assays. Results The colonization sites by V. cholerae on soft-shelled turtles surfaces was clustered. More V. cholerae strains colonized on turtle's calipash and carapace on dorsal side and less strain colonized on ventral side. The competition colonization assays showed that colonization ability of O1 serogroup mshA mutant strains were 7.26 times lower than VC1897dlacZ. Besides, the CI value (O139/O1) of 11 out of the 16 competition groups were greater than 2 (between 2.07 and 59.84). Two groups showed values of 1.43 and 0.93 respectively and 3 groups lower than 0.7. Conclusion The preferred colonization sites for O1 V. cholerae strains on body surface were observed.MSHA was one of the main colonization factors for its colonization. Our study suggested that in general, O139 V. cholerae strains have stronger colonization ability than O1 strains. Besides, strains isolated from soft-shelled turtles tend to have stronger colonization ability than strains isolated from patients. Key words: Vibrio cholerae; Vibrio cholerae O1; O139 vibrio cholerae; soft-shelled turtle