Vibrio cholerae No-01 toxigénico / Toxigenic Vibrio cholerae non-01

The antimicrobial susceptibility and the presence of a heat-stable toxin were researched into 100 non-01 Vibrio cholerae strains sent by 7 different health centers to the National Reference Laboratory of Acute Diarrheal Diseases in "Pedro KourÝ" Tropical Medicine Institute. The presence of 20 toxigenic non-01 Vibrio cholerae was detected, a figure substantially higher than that reported in other geographic areas, except for endemic areas. This result will make it possible to set epidemiological alert in Cuba because these strains can be infected by CTX phages (element transporting genes that encode for choleric toxin) which will give such strains an epidemic potential similar to that of the etiologic agent of cholera. The identified strains could be studied as possible cholera vaccine candidates.

Comparison of the sensitivity & specificity of a polyclonal versus monoclonal capture antibody based Bead ELISA for direct detection of cholera toxin from stool specimens.

This study was conducted to examine whether substitution of polyclonal anti-CT IgG (PAb) coated beads with monoclonal anti-CT IgG, (MAb) coated beads would enhance the sensitivity and specificity of the Bead ELISA for direct detection of CT in stool samples of cholera patients. Sensitivity of MAb Bead ELISA was found to be more efficient (92.7%) than the PAb Bead ELISA (88.2%) in comparison to the 'gold standard' method of conventional culture method (CM). However, the MAb based Bead ELISA had lower specificity (45%) than that of PAb Bead ELISA (51.8%). Further, the positive predictive value was also lower in MAb Bead ELISA (69.9%) as compared to PAb Bead ELISA (82.1%). Generally, all the statistical evaluation demonstrated better agreement between PAb (77.9%) and MAb (72.6%) Bead ELISAs in direct detection of free CT and culture method in confirming the causative organism i.e., Vibrio cholerae in stool specimens. When the two assay systems, viz., PAb and MAb Bead ELISAs were compared, the superiority of the PAb Bead ELISA over MAb Bead ELISA was clearly evident as it had 82.4 per cent of agreement value.

Serovar, biotype, phage type, toxigenicity & antibiotic susceptibility patterns of Vibrio cholerae isolated during two consecutive cholera seasons (1989-90) in Calcutta.

Characteristics of V. cholerae isolated from patients of acute secretory diarrhoea admitted to the Infectious Diseases Hospital, Calcutta during two consecutive cholera seasons (1989 and 1990), with special emphasis on biotyping and toxigenicity, were investigated. The isolation rates of V. cholerae during 1989 and 1990 were 78 and 85.1 per cent respectively, with Inaba serotype dominating in 1989 and Ogawa in 1990. All the V. cholerae 01 strains isolated in this study belonged to biotype Eltor with phage type 4 dominating (48.8%). Most of the strains of V. cholerae were resistant to 10 and 150 micrograms/ml of 0/129 vibriostatic agent. Similarly, majority of the V. cholerae strains were resistant to furazolidone (95.7%), cotrimoxazole (83%) and tetracycline (63.1%) and several resistance patterns were encountered. All the V. cholerae 01 strains examined produced cholera toxin (CT) in amounts ranging between greater than 70 pg/ml and greater than 2.5 ng/ml. In contrast, all but one of the non-01 strains isolated in this study did not produce CT. Further studies are required to elucidate the mechanism involved in the pathogenesis of non-01 V. cholerae mediated diarrhoea.

Evaluation of ELISA and GM1-ELISA for detection of Salmonella enterotoxin.

The ELISA and GM1-ELISA, by using antiserum to purified Salmonella enterotoxin (SE), were standardized and carried out to screen salmonellae isolated from foods of animal origin for enterotoxigenicity. Of the 101 strains of Salmonella belonging to 15 different serogroups tested, 76 (75.24%) strains from 13 serogroups were found enterotoxigenic. ELISA correlated well with rabbit ligated ileal loop (RLIL) test for the detection of enterotoxin producing salmonellae with 24 test strains. ELISA also yielded positive reaction with 7 of 13 RLIL negative strains. GM1-ELISA could not be carried out as none of the 101 cell free culture supernatants (CFCS) were able to bind with GM1-ganglioside. ELISA and GM1-ELISA were also standardized with antiserum to cholera toxin for the detection of salmonellae producing cholera related enterotoxin. None of the 101 strains was found to produce cholera related enterotoxin. ELISA could detect as low as 15 ng/100 microliters of purified SE and 10 ng/100 microliters of cholera toxin when tested with their homologous antisera.