关键词: 血吸虫病, 钉螺, 微生物, pH值

Abstract: Objective To characterize the structure of the culturable microbial communities in Oncomelania hupensis(O. hupensis), and investigate the effects of environmental pH on the microorganisms cultured from O. hupensis for a reference in microbial control of this snail species. Methods The field-collected negative O. hupensis were randomized to neutral groups (A1, A2), acidic groups (B1, B2), alkaline groups (C1, C2), and a field group (Y) (n=10 in each group). Snails in groups A1, B1, and C1 were maintained in dechlorinated water (pH=7), acidic culture medium (pH=4), and alkaline culture medium (pH=10), respectively, for one week, and those in groups A2, B2, and C2 were treated with the same protocol for two weeks. Snails in group Y were directly dissected upon sampling. The soft snail tissues were collected and used to prepare bacterial suspensions, which were continued for the culture and isolation of aerobic bacteria and fungi, and the total number of bacterial colonies was counted. The Biolog microbial identification system, together with microscopic staining observation, was used to identify the types of microorganisms. Results The total cultivable colony counts within O. hupensis from the field group (Y), neutral groups (A1, A2), acidic groups (B1, B2), and alkaline groups (C1, C2) were (6.106±0.854), (6.520±0.365), (7.002±0.627), (7.434±0.400), (6.928±0.294), (7.233±0.564), and (7.527±0.693) lg CFU/g, respectively. The total colony counts of the alkaline group (C1) and acidic group (B1) cultured for 1 week were higher than those of the neutral group (A1), and the total colony count was higher in alkaline group (C2) than that in neutral group (A2) and acidic group (B2) after being cultured for 2 weeks (all P<0.05). Seven aerobic bacterial species were isolated from O. hupensis, with Rathayibacter tritici, Flavobacterium hydatis, and Kluyvera cryocrescens as dominant strains. Fourteen fungal species were isolated, with Cryptococcus neoformans B, Trigonosporomyces hylophilus, and Trichosporon beigelii A as dominant strains. Conclusion The structure of the culturable microbiota in the O. hupensis undergoes corresponding change from the field habitat to the laboratory-rearing setting. Alkaline condition may enhance the diversity of cultivable aerobic bacteria in the snails, yet ecological significance of environment for O. hupensis survival remains to be further elucidated. 

Key words: Schistosomiasis, Oncomelania hupensis, Microorganisms, pH value