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Background & objectives: Bacillus cereus is one of the pathogens responsible for human diarrhoea, mainly due to consumption of contaminated food. The present study was undertaken to determine the occurrence of B. cereus among diarrhoeal patients and its phenotypic and genetic characteristics that determine the virulence and clonal features. Methods: Stool specimens were collected for two years from acute diarrhoeal patients attending the two referral hospitals in Kolkata. Presence of virulence genes in B. cereus was determined by PCR. Clonality was assessed by pulsed-field gel analysis (PFGE) by restriction digestion with SmaI and NotI enzymes. Enterotoxins were detected by haemolysin assay and using BCET-RPLA kit. Invasion assay was done on Hep-2 cell line. Antimicrobial susceptibility was tested by disc diffusion method. Results: B. cereus was identified in 54 (3.5%) of the 1536 diarrhoeal cases studied. Majority of the isolates were susceptible to many antibiotics but showed resistant to amoxyclav and cephalosporins. Six genes covering the two different enterotoxic complexes determining the pathogenicity of B. cereus have been characterized by PCR. The nhe genes were detected in a higher proportion than hbl. Except in two, clonal diversity was noticed among 21 B. cereus isolates. Haemolytic enterotoxin was detected in 76 per cent of the isolates. Majority of the isolates (67%) produced in vitro enterotoxin (BCET) confirming its involvement in the infection. Interpretation & conclusions: Though the presence of B. cereus was not high in patients with diarrhoea, several virulence factors confirm their association with diarrhoea. Distinct clonality was identified in majority of the isolates indicating their origin from different sources. [ABSTRACT FROM AUTHOR]

Chronological analysis of 125 Vibrio cholerae O139 strains isolated during 1993–2005 in Kolkata revealed the prevalence of two new genotypes of cholera toxin (CT) and novel combinations of ctxB and rstR alleles resulting in variant CTX prophages. One of the new genotypes of ctxB, which first appeared in 1996 with the re-emerged V. cholerae O139 strains that had CTX Calcutta phage, was designated as genotype 4. In 1998, another new genotype, designated as genotype 5, was detected that prevailed mostly in CTX phages with El Tor rstR. The prototype El Tor CTX phage with genotype 3 gradually disappeared in O139, and since 2002 the predominant CTX prophages in O139 are Calcutta phages with genotype 4 and El Tor phages with genotype 5. Results showed that V. cholerae O139 strains of Kolkata, isolated over a decade, harboured CTX prophages in the large chromosome having no RS1 downstream of CTX prophage. During the course of its intermittent incidence over a decade, five types of O139 strains were detected based on CT genotypes. Such abrupt genetic changes in O139 strains might not favour its continued prevalence in human cases in Kolkata, India. [ABSTRACT FROM AUTHOR]

Clin Microbiol Infect Abstract Culture-independent identification of diarrhoeal aetiological agents was performed using DNA harvested from diarrhoeal stool specimens with SYBR-Green-based real-time PCR targeting Vibrio cholerae, Vibrio parahaemolyticus, Campylobacter spp., Shigella spp. and three different pathotypes of diarrhoeagenic Escherichia coli. Conventional culture-dependent methods detected bacterial enteropathogens in 68 of 122 diarrhoeal stool specimens. Of 68 specimens, 59 (86.8%) had a single pathogen and the remaining nine (13.2%) had polymicrobial infections with multiple pathogens. Re-analysis of the 68 specimens by culture-independent real-time PCR methods showed that 25 (36.8%) specimens contained single pathogen and 43 (63.2%) specimens contained mixed infections with multiple pathogens. The prevalence of such high levels of polymicrobial infections would not have been detected without using real-time PCR. Culture-dependent analysis assigned 54 of the 122 selected archived specimens as 'no known aetiology'. However, re-analysis of these samples by real-time PCR showed the presence of single or multiple pathogens among 34 (63%) of these specimens. Estimation of relative pathogen load by real-time PCR in the stool specimens indicated that the inability of conventional culture-dependent methods to detect the pathogens was related to lower colony-forming units of the pathogen, as reflected by lower Ct values. Detection of high levels of polymicrobial infection by real-time PCR indicates that in the settings like Kolkata and its surroundings, where cholera and other enteric diseases are endemic, the concept of one pathogen one disease might need to be re-evaluated. [ABSTRACT FROM AUTHOR]

The article discusses a study which assessed the efficacy and safety of a modified killed-whole-cell oral cholera vaccine in a population with endemic cholera in India. Several non-pregnant residents of Kolkata aged 1 year or older who participated in the double-blind trial were cluster-randomised by dwelling to receive two doses of the modified vaccine or heat-killed Escherichia coli K12 placebo orally. The study demonstrated that this modified vaccine, which is compliant with the standards of the World Health Organization (WHO), is safe, provides protection against cholera and can be used in children.