Hand washing with soap reduces diarrhoea and spread of bacterial pathogens in a Bangladesh village.

Hand washing with soap and water can prevent the spread of diarrhoeal diseases in areas where comparatively costly interventions, such as supply of safe water and improved sanitation, are not possible. In this study, the practice of hand washing with soap and water was instituted in a periurban slum of Dhaka city, and the surveillance for diarrhoea sustained for a one-year period. Rates of primary and secondary attacks were compared to those of a non-intervention area similar in age structure, economic status, education, and other relevant variables. Rectal swabs of cases and contacts established aetiologies. There was a large (2.6 fold) reduction in diarrhoeal episodes in the intervention area during the observation period. Rates of bacterial pathogens were also lower in the intervention area. Significant reduction in diarrhoeal incidences was observed in all age groups for all pathogens except for rotavirus. These observations if implemented as health policy could reduce the spread of diarrhoeal diseases at low cost in high risk areas.

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.

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.

Plasmid analysis of Shigella dysenteriae type 1 isolates obtained from widely scattered geographical locations.

Plasmid profiles and antimicrobial susceptibility patterns of 343 strains of Shigella dysenteriae type 1, obtained from 18 different geographical locations, were analyzed. Three plasmids, with molecular sizes of 140, 6, and 2 megadaltons (MDa), were present in 94, 98, and 96%, respectively, of the 343 strains isolated during either epidemic or nonepidemic periods from 1965 to 1987. In addition to these plasmids, 83% of the strains harbored a 4-MDa plasmid and 25% harbored a 20-MDa plasmid. Various plasmid profiles were observed in which the 140-, 6-, and 2-MDa plasmids occurred commonly, irrespective of the place of isolation and drug resistance pattern of the strains. Certain profiles showed significant association with drug resistance patterns. These findings suggest that three plasmids, of molecular sizes 140, 6, and 2 MDa, are unique to S. dysenteriae type 1 strains and may indicate the global spread of a pathogenic bacterial clone. Additionally, these core plasmids, plus plasmids of various other sizes, could be used to identify emerging subclones which are causing both epidemic and sporadic disease. Thus, plasmid profiles of S. dysenteriae type 1 strains can be used to monitor possible pandemic strains as well as individual epidemic strains.

Plasmid profile as a useful marker of a Shigella dysenteriae type 1 strain causing an epidemic of shigellosis.

Plasmid profiles of 60 Shigella dysenteriae type 1 isolates obtained during an epidemic period (April - October 1983) were compared with that of 74 other Shigella species isolated during the same period of time and also with that of 20 S. dysenteriae type 1 isolates obtained before the epidemic period (1969 - 1982). All samples were collected during an epidemic of shigellosis from diarrhoeal patients being treated at the Dhaka Treatment Centre of the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) between April and October 1983. Approximately 4% of the patients were sampled. The isolated showed varied patterns of resistance to several antimicrobial agents. Ninety-two per cent of the 60 S. dysenteriae type 1 strains showed a typical profile of four plasmids with masses of 140, 6, 4 and 2 megadaltons (Mdal). The finding is in contrast with that of a previous study at the ICDDR,B, in which 14 different plasmid profiles were observed in 23 strains of S. dysenteriae type 1 isolated during a 10 - month period in 1982. The profile typical for this study was different from those found in other species of Shigella isolated at the same time. There was a strong association between the possession of this plasmid profile and resistance to chloramphenicol, streptomycin, tetracycline and trimethoprim - sulphamethoxazole. Twenty S. dysenterae type 1 strains isolated from the faeces of patients at the ICDDR,B during 1969 - 1982 were also analysed for their plasmid profiles. The finding is in contrast with that of the epidemic strains. The typical epidemic plasmid pattern, i.e. the 140, 6, 4 and 2 Mdal, was absent in isolates obtained before 1983 epidemic.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Immunobiological relationships between Vibrio fluvialis and Vibrio cholerae enterotoxins.

A total of 26 strains of Vibrio fluvialis was included in this study, which were isolated from patients with diarrhoea and other sources. The GM1 enzyme linked immunosorbent assays performed with the culture filtrates of V. fluvialis yielded negative results, indicating that their receptor site is different from that of the known labile toxin. The cholera antitoxin failed to neutralize the skin permeability factor activities of all the V. fluvialis culture filtrates and none of the concentrated culture filtrates gave any precipitin band, when tested against the cholera antitoxin in Ouchterlony's gel diffusion test. These observations suggest that the toxin of V. fluvialis differs from the known cholera toxin in receptor site, mode of action and antigenicity.

Rotavirus as an important cause of diarrhoea in a hospital for children in Dammam, Saudi Arabia.

A major cause of morbidity and mortality among children in developing countries is acute diarrhoea and rotavirus, a reovirus-like agent, is found to be a leading causative agent. We report here the incidence of rotavirus infection among infants and young children with gastro-enteritis treated at the Children's Hospital in Dammam, Kingdom of Saudi Arabia. One hundred and fifty children, aged between 1 and 60 months, suffering from diarrhoeal illness, were selected as the study cohort; another 150 hospitalized children of the same age group, but not suffering from diarrhoea, served as controls. Sixty-two per cent of the study children complained of watery diarrhoea and 39% of vomiting; all had mild to moderate dehydration. Seventy-two per cent had fever and 30% associated respiratory illness. Worst affected were those 7-12 months old, among whom rotavirus was detected by ELISA techniques in 39.6%, compared with 7.5% of the control children of comparable age group. We could not detect any rotavirus from control children aged over 36 months, whereas approximately 15% of the study children in this age group yielded rotavirus from the stool. The second most common pathogen isolated was Shigella ssp. It was isolated from 18.7% of children under study as against 3% of the controls.

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.

Plasmid characterization of Shigella spp. isolated from children with shigellosis and asymptomatic excretors.

Strains of Shigella dysenteriae type 1 and Sh. flexneri isolated during 1981-82 from children with shigellosis and also from asymptomatic excretors were examined for drug resistance and for the presence of plasmids. Shigella strains isolated from dysenteric children showed multiple plasmid bands. Thirty-eight percent of the strains transferred the drug resistance factor(s), either partially or fully to a recipient Escherichia coli K12 strain. Plasmids in the molecular weight range from between 44-76 Mdal were correlated with drug resistance. It was found that multi-resistant clinical isolates generally harbour a single large transmissible plasmid. Strains isolated from asymptomatic excretors demonstrated plasmid patterns different from those isolated from children with shigellosis although the bands were relatively homogeneous within each group. Both the groups showed the presence of a 140 Mdal plasmid band conferring invasiveness and such strains gave a positive Sereny test. This study thus shows that Shigella strains from asymptomatic excretors also retain invasiveness.

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.