Molecular comparison of toxigenic clinical & non-toxigenic environmental strains of Vibrio cholerae O1 Ogawa isolated during an outbreak of cholera in south India.

BACKGROUND & OBJECTIVES: While investigating a cholera outbreak in south India, toxigenic and nontoxigenic strains of Vibrio cholerae O1 were isolated from patients and from the environment, respectively. This study was performed to compare the genetic relatedness of the patient and environmental strains to determine clonal relationships among these strains and thereby determine the source of the cholera outbreak. METHODS: The 16 strains of V. cholerae isolated from hospitalized patients and 8 environmental V. cholerae strains isolated from the environment were phenotypically and genotypically characterized using a variety of standard techniques. RESULTS: Sixteen toxigenic clinical strains and 2 nontoxigenic environmental strains belonged to O1 serogroup, Ogawa serotype and El Tor biotype. The remaining 6 nontoxigenic environmental strains were classified as non-O1, non-O139 V. cholerae. The drug resistance pattern of the clinical and environmental strains of V. cholerae showed marked differences with the patient strains being resistant to more number of drugs as compared to the environmental strains. DNA fingerprinting of the strains showed considerable diversity between toxigenic clinical and nontoxigenic environmental O1 Ogawa isolates and between the O1 and non-O1, non-O139 isolates. INTERPRETATION & CONCLUSION: In this outbreak of cholera, the O1 strains of V. cholerae from clinical and environmental sources belonged to two different clones and the environmental strains could perhaps be the future cholera outbreak causing clones.

A simplified procedure for rapid screening of vibrios for cholera toxin production.

Conventional methods for the detection of cholera toxin (CT) production by vibrios are not readily available to most laboratories. A modification is described here of a simplified method standardised earlier and based on the degradation of nicotinamide adenine dinucleotide (NAD) by CT; this is simple and can be carried out in small laboratories also. It is also easy to perform, and gives reproducible results.

Possibility of public health hazards by contamination of toxin producing Vibrio cholerae through fishes reared in sewage fed fishery.

This study was undertaken to explore the possibility of contamination of Vibrio cholerae serogroups 01 and 0139, the most important causative organisms for life threatening acute secretory diarrhoea and also potential public health importance, by isolating these organisms from body surface, gill and intestine of common table fishes like Labeo rhoita, Catla Catla, Cirrhinus mirgala and Tilapia mosambica which were reared in sewage and raw human excrita enriched fishery ponds. Vibrio Cholerae 01 or 0139 were not isolated from body surface swabs, gills and intestine of these common table fishes. Water samples of sewage enriched fishery ponds and sewage of Calcutta municipal corporation were also processed for isolation of these organisms, however, these samples were also negative for V. Cholerae 01, 0139 and non 01-0139 serogroups. Present study indicated that there was less chance of contamination of toxigenic and disease producing strains of V. cholerae by common table fishes which were reared in sewage and raw faecal matter enriched fishery ponds.

Comparative analysis of factors promoting optimal production of cholera toxin by Vibrio cholerae O1 (classical & E1Tor biotypes) & O139.

Various culture media [AKI, Brain heart infusion broth (BHI), Casamino acid-yeast extract broth (CAYE), Casamino acid-yeast extract broth supplemented with 90 micrograms/ml of lincomycin (CAYE-L), Tryptic soy broth (TSB) and Yeast extract peptone (YEP)], cultural conditions (stationary and shaking) and incubation temperatures (30 degrees C and 37 degrees C) were evaluated to determine optimal conditions for production of cholera toxin (CT) by different biotypes (classical and E1Tor) and serogroups (O1 and O139) of V. cholerae. It was found that V. cholerae O1 E1Tor grown in CAYE-L and incubated at 30 degrees C with constant shaking was optimal for production of CT, while for the classical biotype and for the O139 serogroup, CT was maximally produced when grown in YEP and incubated at 30 degrees C in a shaker. Temperature appeared to be a prominent factor affecting the production of CT by the O1 E1Tor biotype when the media used were AKI, CAYE-L and YEP and also for the classical biotype when the media used were the AKI, BHI, CAYE and YEP. In the case of the O1 E1Tor biotype, CAYE-L was the best medium for CT production whereas for the classical biotype, CAYE-L was a poor medium as far as CT production was concerned. Irrespective of the media used, 30 degrees C shake culture condition seemed to be more favourable for supporting CT production except in CAYE medium for the O1 E1Tor biotype where incubation at 37 degrees C in a shaker was as good as incubation at 30 degrees C.

La inmunología del cólera y la biología molecular de la toxina colérica: progresos recientes y perspectivas futuras / The immunology of the cholera and th molecular biology of toxins

Recientemente Vibrio cholerae ha llamado mucho la atención de los investigadores por ser un inmunógeno muy potente y, al mismo tiempo, un coadyuvante inmunomodulador de la respuesta inmunitaria en la mucosa intestinal, tanto para los antígenos que se administran mezclados como los ligados covalentemente a la toxina colérica. La inmunopatogenia del cólera es un fenómeno complejo. En este artículo se comunican los resultados preliminares de experimentos realizados con ratas de laboratorio para conocer la respuesta intestinal de la IgA en los roedores y los humanos

La inmunología del cólera y la biología molecular de la toxina colérica / The cholera immunology and the molecular biology of the toxin cholera

La toxina colérica (TC) y su análoga enteroxina termolábil (TL) de la Escherichia coli tienen varios efectos inmunomodulares, que podría explicar su acción adyuvante para estimular la síntesis de la IhA secretora, después de la inmunización bucal. En un modelo murino experimental esos efectos incluyen: la presentación más eficiente de los antígenos por los macrófagos y otras células B con una síntesis incrementada de IgA y otros efectos importantes sobre la proliferación de los linfoscitos T y su producción de linfocinas (interleucinas). La capacidad coadyuvante se debe a que la TC tiene una acción ribolisante de ADP, que lleva a un incremento del AMP cíclico en la célula afectada y por ello pudiera ser difícil de eliminar la enterotoxicidad, sin pérdida de su capacidad adyucante; sin embargo, se ha demostrado que la TC y la subunidad atóxica B (TCB) tienen la propiedad de facilitar la respuesta inmunitaria de la mucosa ante la presencia de varios epitopos o antígenos adyuvantes que pudieran servir como vehículo para inducir una respuesta específica de IgA secretora, ante un límite muy amplio de antígenos para la vacunación humana contra el cólera y otras infecciones entéricas

Neutralisation of the new cholera toxin by antiserum against crude enterotoxin of cholera toxin gene-positive Vibrio cholerae 01 in rabbit ileal loop model.

The enterotoxicity of the new cholera toxin (NCT) prepared from cholera toxin gene-negative (CT-) V. cholerae 01 strains isolated from human diarrhoeal and environmental sources was assayed in rabbit ileal loops and the toxin unit was calculated to be 24 micrograms of protein. The enterotoxicity of the NCT preparations were completely neutralised by the antiserum raised against the enterotoxin preparation from the CT+ V. cholerae 01 strain 569B at 1 in 16 dilution in ileal loops. The antiserum contained 1 unit of antitoxin in 85 x 10(-4) ml amount. The data indicate that the antiserum prepared against the enterotoxin of CT+ strain contains antibody against the NCT and can neutralise the toxin in vivo. The observations also suggest that CT+ strains liberate the NCT simultaneously with CT and the latter gets eliminated during the process of purification.