Effects of undernutrition on infection with Vibrio cholerae O1 and on response to oral cholera vaccine.

The association between undernutrition and the risk of colonization and disease with Vibrio cholerae O1, concentrations of salivary IgA and the serologic response to infection and to orally administered cholera B subunit were examined prospectively in a family study in Bangladesh. Children ages 1 to 8 years who were family contacts of patients hospitalized with culture-confirmed cholera were visited within 24 hours of the hospitalization and daily for 10 days, queried for the presence of diarrhea and cultured for V. cholerae O1. On Day 1 each child was weighed and saliva was collected to measure total IgA. On Days 1 and 21 blood was taken to assess vibriocidal and antitoxin titers, and on Days 1 and 2 B subunit or placebo was given orally as part of a trial to look for a toxin-blocking effect. Of 412 children enrolled in the study 35% (143) became infected with V. cholerae O1 and 49% (70) of these developed diarrhea. Undernutrition, defined in a child as weight less than 70% of the Harvard reference weight-for-age, was not associated with colonization, disease or the duration or severity of cholera. Moreover well-nourished children did not differ from undernourished children in their concentrations of salivary total IgA, initial serum antitoxin or vibriocidal antibodies or in their serologic response to colonization, disease or B subunit. The immune system in its response to cholera appears to be quite resistant to nutritional insults. The good antitoxin response to B subunit among undernourished children is of particular importance in considering the use of future oral cholera vaccines in areas where such undernutrition is common.

A simple laboratory method for the diagnosis of V. cholerae.

In many developing countries where cholera occurs, bacteriological facilities at the local level are lacking and either cholera may be unreported or other diarrhoeal diseases may be mistakenly reported as cholera. A simple and practical method, suitable for use in small hospitals and health centres and by field teams of health workers is described. Swab samples are streaked on to various media (TTGA and TCBS were found to be the most satisfactory), incubated overnight at 35 degrees C and read. The characteristics which distinguish Vibrio cholerae colonies from others developing are described. In tests on 309 cholera patients, culture on TTGA gave 100% and on TCBS 96.7% positives.

Studies on the factors affecting the haemolysin production of Vibrio mimicus isolated from clinical and environmental sources.

The in vitro production of haemolysin by Vibrio mimicus, a newly described aetiological agent for human diarrhoea, was determined using sheep erythrocytes. The effects of medium composition and sodium chloride concentration on haemolysin production and its heat stability were investigated. The haemolysin was produced optimally in brain-heart infusion broth and was unaffected by salt concentration up to 1.5%. However, haemolysin production decreased gradually with increasing concentrations of salt above 1.5%, with no production at 5% NaCl. Haemolytic activity was completely lost when culture supernatants were heated at 56 degrees C for 30 min. In general, clinical strains were more haemolytic than environmental strains. The assay system described is simple and rapid, and can be used to study the pathogenic potential of V. mimicus and other noncholera vibrio strains.

Seasonality of classical and El Tor cholera in Dhaka, Bangladesh: 17-year trends.

Data on the cholera patients admitted monthly to the ICDDR, B, hospital in Dhaka (Bangladesh) from 1964 through 1980 have been studied and analysed. Although Vibrio cholerae variant El Tor did not enter Bangladesh until 1963, it has completely displaced classical cholera since 1973. There have also been changes in seasonality, which are discussed.

Isolation of Yersinia enterocolitica and Y. intermedia from fatal cases of diarrhoeal illness in Bangladesh.

From three fatal cases of diarrhoeal illness in Bangladesh, Yersinia species were isolated from tissues at post-mortem examination. One patient was infected with Y. enterocolitica serotype 0:7, 8 and two patients were infected with Y. intermedia. These patients were infected also with other enteric pathogens. These findings suggest that Yersinia may be important as pathogens in tropical diarrhoea and as co-pathogens in serious disease.

Replacement of intravenous therapy by oral rehydration solution in a large treatment centre for diarrhoea with dehydration.

PIP: In this study the efficacy of oral rehydration solution (ORS) was compared with that of intravenous fluid (IVF) in the treatment of moderate and some severe cases of dehydration due to diarrhea in a treatment center in Bangladesh during 1980-81. 10,379 patients with moderate and severe dehydration in 1980 and 9897 in 1981 were studied, most were under age 5. Almost all uncomplicated diarrhea patients with moderate and severe dehydration admitted in 1980 were initially treated with IVF followed by ORS. The average amounts of IVF, ORS, and total fluid used/patient (based on a 10% sample of patients) were 1.26, 0.10, and 1.36 litres respectively in 1980 and 0.65, 1.16, and 1.81 litres in 1981. As of December 1980 only patients with pulselessness, shock, and vomiting were given IVF. In 1981, 94% of severe cases of dehydration were treated with IVF plus ORS compared to 100% in 1980 (p0.01) and 6% were treated with ORS alone compared to 0% in 1980 (p0.01). Among moderate cases of dehydration, 29% received IVF plus ORS in 1981 (92% in 1980) and 71% were successfully treated with ORS alone (8% in 1980). The percentage of patients staying for over 12 hours in the treatment center was 29.9% in 1980 and 42.1% in 1981. Among the patients staying less than 12 hours the mean duration of stay was 6.02 +or- 3.18 hours in 1980 and 6.73 +or- 3.35 hours in 1981, significant at the 0.001 level. IVF is shown to be effective in treating dehydration but costs more and presents greater risks including the introduction of septicaemic infection, pyrogenic reactions, embolism, phlebitis, thrombosis, and even rupture of the veins. ORS treatment is simple, safe, less costly, and can be taught to parents. No children treated with ORS died, but some IVF patients did, suggesting that only ORS therapy is fully effective. Average cost per patient in the treatment center was US$6.60 in 1980 and US$4.40 in 1981, a savings of 33.3%. Replacement of IVF by ORS led to the conclusion that developing countries should make ORS services available throughout the country in order to reduce hospital admissions and mortality.^ieng

Electropherotyping of plasmid DNA of different serotypes of Shigella flexneri isolated in Bangladesh.

One hundred and twenty-five Shigella flexneri strains, isolated during January-December 1984, at the Dhaka treatment centre of the International Centre for Diarrhoeal Disease Research, Bangladesh, were serotyped using absorbed rabbit antisera specific for all type- and group-factor antigens, as well as a group of ten mouse and rat monoclonal antibodies. Electropherotypes of the plasmid deoxyribonucleic acid (DNA) were also determined. S. flexneri 2a was the predominant serotype followed by 3b, 1a, and 2b. The recently described E1037 antigen was also found in three strains of S. flexneri serotype 6. Electropherotyping of the plasmid DNA showed that three plasmids of approximately 140, 2.7, and 2 megadalton (MDa) were present, respectively, in 97, 97 and 94% of the 125 strains. Additional plasmids of various other sizes were also present in different serotypes except in serotype 2a. The additional plasmids again appeared to be specific for that particular serotype. For example, all 12 strains of S. flexneri 2b harboured an additional plasmid of approximately 1 MDa. Thus, electropherotyping of plasmid DNA of different serotypes of S. flexneri might be useful to differentiate S. flexneri from other species of Shigella and in identifying different serotypes of S. flexneri. Therefore, the common plasmids, plus the additional plasmids, could be used to identify epidemic, as well as sporadic, subclones of S. flexneri strains.

Breast-feeding children in the household as a risk factor for cholera in rural Bangladesh: an hypothesis.

Vibrio cholerae 01 produces symptomatic and asymptomatic infections. In this study, we investigated a cholera epidemic in northern Bangladesh to specifically search for risks of developing symptomatic infection. A case-control study in six villages found that cases were more likely than controls to have in their family a child who was still breast-feeding and who had been asymptomatic during the epidemic. Among 24 case-control pairs with cholera-like diarrhea as cases, there were 11 discordant for the presence of such a child in the family, in 9 of them, the child was in the case-family (relative risk = 4.5, p = 0.033). Among 13 case-control pairs with laboratory-confirmed cholera as cases, there were 7 discordant for the presence of a breast-feeding child, and in 6 of them, the child was in the case-family (relative risk = 6, p = 0.06). Breast-feeding children in this area are usually kept naked, and defecate onto a cloth pad held against their buttocks by a family member who may be repeatedly exposed to the soiled cloth. Symptomatic infection with V. cholerae may depend on exposures to situations that augment the ingested dose of V. cholerae, and these findings led us to hypothesize that breast-feeding children, if infected, may play a substantial role (attributable risk = 55%) in facilitating such transmission in rural Bangladesh.

Simultaneous classical and El Tor cholera in Bangladesh.

PIP: Cholera appears annually in Bangladesh, with peak incidence from September through December and April through June. After being absent for a decade, the classical biotype of Vibrio cholerae reappeared in Commilla and Dhaka on September 1 and 3, 1982, and soon thereafter appeared in many other districts. Cases due to the newly emerged classical biotype of V. cholerae rapidly surpassed those due to the El Tor biotype. Before 1970, classical V. cholerae had been responsible globally for both endemic and epidemic cholera. In Bangladesh, El Tor was first isolated in 1964. By 1973, it has replaced the classical strain. Subsequently until 1981, only 6 classical isolates were noted. The new classical strains were almost identical to those isolated a decade earlier, except for their ability to successfully displace El Tor in an epidemic setting. Investigation of the first 10 cholera cases suggests a multiple source outbreak. The age distribution of the classical and El Tor was similar, suggesting a lack of important new antigenic determinants, which could circumvent existing immunity in the population. Both strains followed known seasonal patterns.^ieng

Isolation of enterotoxigenic, hemolytic, and antibiotic-resistant Aeromonas hydrophila strains from infected fish in Bangladesh.

Strains of Aeromonas hydrophila isolated from skin infections of common freshwater fish in Bangladesh were tested for enterotoxin production, hemolysin production, and any correlation between these two activities. We also tested the resistance patterns of A. hydrophila to different drugs, especially in relation to ampicillin. The A. hydrophila strains produced an enterotoxin that was related to their beta-hemolytic activities. Production of beta-hemolysin may thus be an indicator of enterotoxicity. As 50% of the strains of A. hydrophila were found to be susceptible to 12.5 micrograms of ampicillin per ml, media containing this antibiotic may not be suitable for their isolation.

Usefulness of plasmid profiles for differentiation of Shigella isolates in Bangladesh.

We studied the plasmid profiles of 136 Shigella isolates in Bangladesh to determine whether plasmid profiles could be used for differentiation of strains for epidemiological studies. Many different plasmid patterns were observed within each species, indicating that many genetically different strains of Shigella are responsible for illness in Bangladesh.

Influence of water temperature, salinity, and pH on survival and growth of toxigenic Vibrio cholerae serovar 01 associated with live copepods in laboratory microcosms.

The influence of water temperature, salinity, and pH on the multiplication of toxigenic Vibrio cholerae serovar O1 cells and their attachment to live planktonic crustaceans, i.e., copepods, was investigated by using laboratory microcosms. By increasing water temperatures up to 30 degrees C, a pronounced effect on the multiplication of V. cholerae was demonstrated, as was attachment of the cells to live copepods. These were measured by culturable counts on agar plates and direct observation by scanning electron microscopy, respectively. Of the three salinities examined (5, 10, and 15%), maximum growth of V. cholerae and attachment to copepods occurred at 15%. An alkaline pH (8.5) was optimal both for attachment and multiplication of V. cholerae, as compared with pH 6.5 and 7.5. It is concluded that conditions affecting attachment of V. cholerae serovar O1 to live copepods observed under laboratory conditions may also occur in the natural estuarine environment and, thereby, are significant in the epidemiology of cholera.

Risk factors for death in complicated diarrhoea of children.

A total of 1330 children with complicated diarrhoea who were admitted to the general ward of the International Centre for Diarrhoeal Diseases Research, Bangladesh Health Complex, during 1979 were examined. The risk of death by complication of diarrhoea, aetiology, age, and nutritional state was analysed by a logit regression model. Serum sodium concentration and coma were found to be significant predictors of death, death being related directly to coma and inversely to serum sodium concentration. An earlier study had shown that the incidence of hyponatraemia was directly related to the degree of malnutrition, but the results of logit regression analysis did not show the nutritional state to be a predictor of death. Owing to lack of data, however, serum albumin concentration could not be taken as a variable in the logit regression analysis. To determine the relation of serum albumin concentration to hyponatraemia and the cause of death in hyponatraemia further prospective studies would be necessary.