Sequence polymorphisms of rfbT among the Vibrio cholerae O1 strains in the Ogawa and Inaba serotype shifts

Abstract

BackgroundVibrio cholerae serogroup O1 has two major serotypes, Ogawa and Inaba, which may alternate among cholera epidemics. The rfbT gene is responsible for the conversion between the two serotypes. In this study, we surveyed the sequence variance of rfbT in the Ogawa and Inaba strains in China over a 48-year (1961-2008) period in which serotype shifts occurred among epidemic years.ResultsVarious mutation events including single nucleotide, short fragment insertions/deletions and transposases insertions, were found in the rfbT gene of the Inaba strains. Ectopically introducing an intact rfbT could overcome the mutations by converting the Inaba serotype to the Ogawa serotype, suggesting the effects of these mutations on the function of RfbT. Characteristic rfbT mutations were recognized in the Inaba strains among Inaba serotype dominant epidemic years which were separate from the Ogawa dominant epidemics. Three distinguishable mutation sites in rfbT between the classical and the El Tor biotype strains were identified and could serve as biotype-specific biomarkers.ConclusionsOur results provide a comprehensive picture of the rfbT gene mutations among the V. cholerae O1 strains in different epidemic periods, which could be further used as the tracing markers in clonality analysis and dissemination surveillance of the epidemic strains.

Development of Stable Vibrio cholerae O1 Hikojima Type Vaccine Strains Co–Expressing the Inaba and Ogawa Lipopolysaccharide Antigens

“…Accession number JX565662) where the phenotype is reported as Inaba. We have found the same mutation in additional Inaba strains in our strain collection [17] and this specific wbeT mutation has been reported also by other groups as associated with the Inaba serotype [18] , [19] . No other mutations associated with a Hikojima phenotype have been defined.…”

Vibrio choleraeType VI Secretion System Auxiliary Cluster 3 is a Pandemic-associated Mobile Genetic Element

“…Truncation of int E appears to have occurred by insertional sequence (IS5 element) interruption to form int P . IS5 elements have been shown to drive rapid adaptation in response to environmental stress through either transcriptional regulation of nearby genes or through insertional inactivation (46)(47)(48)(49). Here we show that the IS5-truncated int P is expressed at much lower levels than the full-length int E , despite having the same promoter and induction conditions.…”

The Transmission and Antibiotic Resistance Variation in a Multiple Drug Resistance Clade of Vibrio cholerae Circulating in Multiple Countries in Asia

“…From 1961, three cholera epidemics have been recognized based on the epidemiological surveillance, with a maximum of about 40,000 cases in the peak years[ 7 , 8 ]. However, after 2005, reports of cholera decreased dramatically to less than 200 cases per year[ 7 , 8 ]. Although sporadic cases were still recorded, there was no major (> 100 reported cases) O1 cholera outbreak reported in National Disease Surveillance System in China.…”

“…Two other peaks of cholera clinic cases were recorded in China in 1980s and 1990s[ 7 , 8 ], which were both sinks of transmissions from South Asia. The number of cholera cases in China decreased dramatically since 2000, and some ‘minor’ cholera outbreaks (tens to hundreds of cases reported in each) caused by O1 serogroup strains were reported[ 7 , 8 ]. For example, in 2008, from late-September to mid-November, 90 cholera cases were reported in Hainan, an island at south of China.…”