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“Background Vibrio cholerae is the causative agent of the diarrheal disease cholera.

Out of the 200 serogroups of V. cholerae, only two biotypes of serogroup O1 (classical and El Tor) and serogroup O139 cause severe CHIR-99021 Palmatine diarrhea and epidemic cholera [1], although not all strains in these two serogroups are pathogenic. Toxigenic and nontoxigenic V. cholerae strains are genetically diverse. The toxigenic strains form a genetically Torin 2 nmr homogenous group, while nontoxigenic strains are heterogeneous and may have diverse origins [2–4]. The nontoxigenic strains, which are usually isolated from environmental sources such as sewage, oysters, and brackish water, do not carry cholera toxin (CT) and other major virulence genes necessary for human pathogenesis [5]. V. cholerae is capable

of metabolizing many types of carbohydrates. Previously, we found that not only is D-sorbitol metabolized by V. cholerae, but it is also fermented at different rates by the toxigenic and nontoxigenic El Tor strains. The toxigenic strains have a low sorbitol fermentation rate and are called slow-fermenting strains, whereas the nontoxigenic strains have a faster sorbitol fermentation rate and are called fast-fermenting strains [6]. The sorbitol fermentation test is included in the Phage-biotyping scheme, which consists of phage typing and biochemical typing and is developed in 1970s in China. This scheme is used to distinguish and type the El Tor strains which are pathogenic and are potential to cause epidemic or not [6].