title: Development of a PCR-restriction fragment length polymorphism assay for detection and subtyping of cholix toxin variant genes of Vibrio cholerae.
abstract: Cholix toxin (ChxA) is an exotoxin reported in Vibrio cholerae non-O1/non-O139. Apart from its prototype (ChxA I) we have recently identified two novel variants of this toxin, ChxA II and ChxA III. Our previous investigations indicated that the first two variants may instigate extra-intestinal infections and ChxA II can be more lethal than ChxA I in mice. However, all three cholix toxins (ChxA I to III) failed to show any enterotoxicity in rabbit ileal loops. In this study we developed a PCR-restriction fragment length polymorphism (RFLP) assay to differentiate all three chxA variants to further understand the importance of each subtype. By using 53 V. cholerae non-O1/non-O139 strains harbouring chxA genes, which were previously categorized by sequencing, and various other strains as negative controls, the PCR-RFLP assay showed 100 % typability and specificity. Furthermore, when applied to differentiate additional V. cholerae strains, which were also screened for the chxA gene by colony hybridization, this assay identified chxA I and chxA II genes among 18.5 % and 4.5 % of non-O1/non-O139 strains (n = 178), respectively. One non-O1/non-O139 strain was untypable due to the insertion of an IS911-like element. Interestingly, the chxA I gene was detected in 10 out of 137 cholera toxin gene-negative V. cholerae O1 strains. These results suggest that the PCR-RFLP assay developed in this study can be a rapid and simple method to differentiate the chxA subtypes.
authors.affiliation: International Prevention of Epidemics, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan.
authors.forename: Sharda Prasad
authors.initials: SP
authors.lastname: Awasthi
authors.affiliation: International Prevention of Epidemics, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Asakura
authors.affiliation: Diarrhoeal Disease Epidemiology and Ecology Department, International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh.|International Prevention of Epidemics, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan.
authors.forename: Sucharit Basu
authors.initials: SB
authors.lastname: Neogi
authors.affiliation: International Prevention of Epidemics, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hinenoya
authors.affiliation: National Institute of Cholera and Enteric Diseases, Kolkata, India.
authors.forename: T
authors.initials: T
authors.lastname: Ramamurthy
authors.affiliation: International Prevention of Epidemics, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Yamasaki
mesh_terms: D020727:ADP-Ribosylation Factors / Q000145:classification* / Q000235:genetics*; D001427:Bacterial Toxins / Q000145:classification* / Q000235:genetics*; D002771:Cholera / Q000382:microbiology; D006801:Humans; D058889:Molecular Typing / Q000379:methods*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012150:Polymorphism, Restriction Fragment Length; D044163:Vibrio cholerae non-O1 / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D001427:Bacterial Toxins; D020727:ADP-Ribosylation Factors; C529269:cholix toxin, Vibrio cholerae