OBJECTIVETo Investigate the differences of sorbitol fermentation related genes and optimize molecular analysis method for distinguishing an epidemic with nonepidemic strains of Vibrio cholerae.

METHODSSequence analysis on four genes of sugar fermentation stimulation protein, periplasmic maltose-binding protein, periplasmic phosphate-binding protein and periplasmic amino acid-binding protein.

RESULTSIn this study, the following data was noticed: for O1 serogroup El Tor biotype V. cholerae, twenty-four epidemic and eight nonepidemic strains were chosen; For O139 serogroup V. cholerae, five epidemic and four nonepidemic strains were chosen. With those genes of sugar fermentation stimulation protein, there were three point mutations. The 106th, 150th, 378th oligonucleotide in epidemic strains were A, A and T, comparing to the nonepidemic strains which were G, G and C. When comparing the protein sequences, epidemic strains had a Threonine at 36th amino acid, whereas nonepidemic strains had an Alanine. The results in O139 serogroup were consistent with those in O1 serogroup El Tor biotype strains. Another two point mutations were found in the genes of periplasmic maltose-binding protein. The 999th, 1003rd oligonucleotides in epidemic strains were A and C, while in nonepidemic which were G and T. For the gene of periplasmic amino acid-binding protein, two point mutations were noticed. The 504th and 690th oligonucleotides in epidemic strains were T and C, but were C and T in nonepidemic. However, no amino acid differences were found in periplasmic maltose-binding protein and periplasmic amino acid-binding protein. For periplasmic amino acid-binding protein gene, there was no difference on oligonucleotide between epidemic and nonepidemic strains.

CONCLUSIONResults suggested that SNPs in these genes might serve as a useful tool to distinguish the epidemic strains from nonepidemic strains. The 36th amino acid mutation of sugar fermentation stimulation protein in epidemic and nonepidemic strains might change the activity of the protein which might be associated with sorbitol fermentation.