ctxB Research Articles

Haitian ctxB producing Vibrio cholerae in Karnataka, India: Emphasis on molecular epidemiology and laboratory networking system

Cholera, a primeval waterborne, severe dehydrating diarrheal disease, caused by V.cholerae , with a considerable health burden especially in developing countries. Due to lack of laboratory based evidences of an etiological agent many outbreaks are recorded as diarrhea outbreaks and cholera as well as V.cholerae El Tor biotype may remain unrecognized. The present report is an effort to trace the circulating strain in the community with the support of laboratory networking system and the aid of molecular techniques in epidemiology. Under Integrated Disease Surveillance Programme [IDSP], Dept of Microbiology Bangalore Medical College and Research Institute is recognized as a state referral laboratory for investigation of outbreaks in linked districts .In the month of July 2016 a total of 06 representative stool samples randomly collected in Cary Blair media from suspected cases of cholera were received for isolation and identification of etiological agent. All stool specimens were processed according to standard protocol and V.cholerae isolates were sent to National Institute for Cholera and Enteric Diseases [NICED] for molecular characterization. V. cholerae was isolated from 05 out of 06 samples tested. Serological tests revealed that all 05 isolates belonged to V.cholerae strain O1 serotype Ogawa. PCR based study from NICED confirmed all the V.cholerae strains contain Haitian ctxB. This molecular epidemiological study under the laboratory networking system revealed the circulation of Haitian variants of V.cholerae in some regions of Karnataka. Since the mortality and morbidity is high with Haitian genotypes than the El tor biotype coordinated and vigilant monitoring of V.cholerae is essential.

Antibiotic resistance and molecular characterization of Vibrio cholera strains isolated from an outbreak of cholera epidemic in Jiangsu province

To assess the antibiotic resistance and molecular characterization of cholera strains and to provide basis for clinical treatment and prevention of cholera. 4 stains isolated from an outbreak of cholera epidemic in Huai'an City in Jiangsu province in September 2010 were characterized using antibiotic susceptibility, biotype analysis, virluence genes detection, ctxB gene sequencing, and PFGE analysis. The 4 strains were all resistant to sulphamethoxazole/trimethoprim, erythromycin, streptomycin. High drug susceptibility of the samples was found to 6 kinds of antibiotics such as amikacin, norfloxacin, ciprofloxacin, gentamicin, chloramphenicol, ampicillin. The isolates expressed phenotypic traits of both serogroup O1 ogawa and El Tor and carried 9 kinds of virulence genes, ctxA, ace, zot, toxR, tcpI, ompU, rtxC, tcpA, and hlyA gene. They were also identified as harboring the classical ctxB genotype based on amino acid residue substitutions. The PFGE profiles of NotI showed a single banding pattern, while SfiI's was 2 banding patterns. The bacterium type of Vibrio cholerae causing the epidemic outbreak of cholera belonged to the atypical EL Tor variant which was also identified as toxicogenic strain. The mapping of the strains prompted that there should be the common contamination source. Drug sensitivity test can guide the clinical drug use, in order to reduce the emergence of resistant strains.

Phenotypic diversity of toxigenic Vibrio cholerae O1 E1 Tor strains identified in China

Objective To understand the phenotypic diversity of toxigenic Vibrio cholerae O1 El Tor strains isolated from different provinces in China during the last 50 years. Methods Traditional biotyping testings including susceptibility to polymyxin B,sensitivity to groupⅣphage, Voges-Proskauer test and haemolysis of sheep erythrocytes were conducted. Results Data from Biotype-specific phenotype analysis revealed that only 133 isolates carryed the typical El Tor phenotypes while the other 251 isolates displayed atypical El Tor phenotypes. Combined with ctxB, rstR genotypes and phenotypic characteristics,64 isolates were identified as typical El Tor biotype,21 were El Tor variants that showing the typical El Tor biotype-specific phenotype but with ctxBclas . 280 isolates were defined as the hybrid groups with traits of both classical and El Tor biotypes that could be further classified into 45 groups,based on the combination of genotypes of ctxB,rstR and phenotypic characteristics. Conclusion Toxigenic Vibrio cholerae O1 El Tor strains that isolated from different provinces in China displayed high phenotypic diversity. The traditional biotype traits could not be used to correctly distinguish the two different biotypes. Key words: Vibrio cholerae; Biotype; ctxB; rstR