Cholera in its present day scenario.

Cholera existed in many parts of the world since olden days. Gangetic delta is considered as the home of the disease. Since 1970 there has been a significant development of the disease with its ecologic and epidemiologic aspects. Vibrio cholerae non-01 strain in taxonomically separated from V cholerae 01 strain. Though 01 strain causes epidemic outbreaks, still non-01 has been implicated to cause cholera like illness. While humans are long considered to be the only reservoir of V cholerae 01 strain, but the organism appears to have a free-living cycle in the natural environment. The organism survives more rapidly in the brackish water than fresh water. It has been demonstrated that V cholerae undergoes conversion to a viable but non-culturable state, whereby the cells are reduced in size, become ovoid, but in contrast to starved cells, do not grow at all on standard laboratory media. Seasonality coupled with starvation response and dormancy phenomenon, reflects the origin of V cholerae as an autochthonous estuary dweller. All biotypes of this organism can grow on media containing chitin as the sole carbon source. Outbreaks of the disease are related to plankton blooms associated with warmer sea-surface temperature. In 1997 V cholerae 01 biotype El tor continued to occur in all regions of the world. In 1982 a new classical variant initially displaced entrenched El tor in Bangladesh and coexisted with it for almost a decade. V cholerae 0139 Bangal has arisen along the Bay of Bengal and has spread in Asia.

Enterotoxicity, haemolytic activity and antibiotic susceptibility of Aeromonas eucrenophila strains isolated from water and infected fish.

Strains of A. eucrenophila isolated from fresh water (2 strains) and infected fish (4 strains) were tested for haemolytic activity and enterotoxicity and any correlation between them. Also, the resistance patterns of A. eucrenophila were tested especially in relation to ampicillin. None of the A. eucrenophila strains caused fluid accumulation in the initial tests, however, they did so only after one to four sequential passages through the gut of a susceptible host. All the strains of A. eucrenophila showed beta-haemolytic activities. Production of beta-haemolysin could be correlated with enterotoxicity. Since all the strains of A. eucrenophila were resistant to ampicillin, media containing this antibiotic may be used for their isolation from diverse sources.

Childhood diarrhoea due to rotavirus in a community.

The etiologic role of rotavirus in acute diarrhoeal illness in children under five years of age was studied over a period of one year in an urban slum community. Rotavirus was detected in 17.7 per cent of 376 children with diarrhoea and 4 per cent of 299 healthy children with maximum prevalence at 19-24 months of age with statistically comparable detection in 0-6 months of age. The overall prevalence was significantly higher in children below 2 yr as compared to those between 2-5 yr of age. Girls (24.1%) were more susceptible amongst the diarrhoeal group in comparison to boys (13.8%). Diarrhoea due to rotavirus was more prevalent during the cooler months (November-February) of the year and no correlation was observed with rainfall and relative humidity. Rotavirus as the sole pathogen was observed in 9 per cent children with diarrhoea and in the rest, association of Cryptosporidium (3%) was observed for the first time with this virus along with other known enteropathogenic bacteria and parasites, enterotoxigenic Escherichia coli being the commonest organism.

Better preservation of Campylobacter jejuni/C. coli in a defined medium.

Campylobacter jejuni and C. coli strains were preserved at -10 degrees C in different stock media to determine their efficacy to preserve the organism for a longer period of time. An improved defined stock culture medium was developed for the organism by removal and effective neutralisation of the toxic metabolites. Comparative study revealed that phosphate buffer saline (PBS), pH 6.7 supplemented with 0.2 per cent charcoal, 0.025 per cent FBP (ferrous sulphate, sodium metabisulphate and sodium pyruvate), 0.1 per cent L-cystein and 10 per cent glycerol could support survival of C. jejuni coli strains for as long as 135 days at -10 degrees C followed by George's medium, brucella broth with 15 per cent glycerol, fetal calf serum with 50 per cent TSYB (tryplicase soy yeast-broth) and glycerol transport broth respectively.

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.

Relationship between multiple drug-resistance & enterotoxin production by Shigella species.

Culture filtrates prepared with strains of Shigella dysenteriae 1 and those of Sh. flexneri and Sh. sonnei, collected from different geographical locations in India caused accumulation of fluid in rabbit gut loops, indicating their capability to produce Shiga and Shiga-like toxins respectively. Sh. boydii strains were noted for the first time to produce Shiga-like toxins. The failure of production of fluid accumulation in rabbit gut by Shigella strains that lacked the R-markers of the antibiotics tested and the gradual enhancement in the secretory response by strains containing R-markers in the increasing order indicate a possible correlation between acquisition of higher number of R-markers and enterotoxic activity. The non-transferable and non-curable nature of most of the drug resistance markers, coupled with the failure of the two transconjugants to elicit a secretory response and the capacity of the single cured variant to retain this property suggest the involvement of certain chromosomal locii in mediating drug resistance and enterotoxicity in Shigella.

Better growth of Campylobacter jejuni using simple Fortner's principle & candle extinction jar.

C. jejuni isolated from patients of childhood diarrhoea and chicken intestines were examined for better growth in both liquid and solid media under three different environments of candle extinction jar with or without an Escherichia coli inoculated plate and three such plates in a sealed jar. Better growth by one log in liquid media was obtained at 24 and 48 h with bacterial counts of about ca. 10(7) and ca. 10(9) respectively, and larger colony size at 24 h on solid medium by inclusion of a single Esch. coli inoculated plate following Fortner's principle rather than candle jar alone. Inclusion of three Esch. coli plates yielded similar results at 48 h but lesser growth at 24 h and a decline at 72 h. Most of the C. jejuni strains failed to adapt to grow in presence of air.