V. I. Mathan

Prevalence of intestinal parasites in rural Southern Indians

objective    To determine the prevalence of intestinal protozoal and helminthic infection in a rural population.method  Seventy‐eight members of 15 families from a village were studied. Stool samples from all subjects were examined on alternate days for one month.results  The overall prevalence rate of various parasitic infections was 97.4%, with only 2 of 78 subjects not excreting parasites in any of their 15 samples. Eighteen (23.1%) persons had only one type of parasite, while 58 (74.3%) excreted multiple parasites. Giardia and Cryptosporidium were the commonest protozoan infections, affecting 42/78 (53.8%) and 31/78 (39.7%), respectively. Hookworm infestations were the commonest helminthic infections, seen in 48/78 (61.5%). Based on excretion patterns, the asymptomatic individuals could be divided into 2 groups of infrequent and frequent excretors, indicating that the host response may determine the level of parasite replication in the gut.

CRYPTOSPORIDIUM AND DIARRHOEA IN SOUTHERN INDIAN CHILDREN

Cryptosporidium was detected more frequently in stool samples from southern Indian children with acute diarrhoea than from matched controls. It was seldom the only pathogen detected and was not associated with clearcut clinical features. The frequency of the protozoon in children under six months of age was higher in controls than in patients with acute diarrhoea. These features suggest that Cryptosporidium is unlikely to be a major cause of acute diarrhoea in this population. Frequency of Cryptosporidium was higher in children who had been given antibiotics and in those with prolonged episodes of diarrhoea. Administration of antibiotics may lead to conditions within the intestinal lumen that favour colonisation by the organism and prolongation of diarrhoeal episodes.

Ultrastructural changes in the upper small intestinal mucosa in patients with cholera

BACKGROUND & AIMS Small intestinal mucosal ultrastructural abnormalities were reported in a limited number of patients with cholera in the 1970s. This study extends these observations by examining distal duodenal biopsy samples from 19 patients with cholera and 10 controls. METHODS Endoscopic biopsy samples obtained, usually during the first 24 hours of illness, were processed for electron microscopy. RESULTS Widening of intercellular spaces and alteration of apical junctional complexes were prominent in the villus epithelium, whereas blebbing of microvillus border and mitochondrial changes were more prominent in the crypt epithelium. The apical junctional and intercellular space changes were not altered by oral rehydration. Degranulation of argentaffin cells, mucosal mast cells, and eosinophils; increase in neutrophil polymorphs; and changes in the enteric nerve fibers and microvasculature were also present. The extent of the changes correlated with clinical severity. CONCLUSIONS The differential involvement of the villus and crypt suggests that factors responsible for secretion may act differentially on surface and crypt epithelium and that both regions may contribute to secretion. The contribution of the enteric nervous system, vasculature, argentaffin cells, mucosal mast cells, eosinophils, and neutrophils in the secretory process and in determining the severity of the clinical illness must be determined by further clinical studies.

Cytomegalovirus infection of the human gastrointestinal tract

Background : Current interest in cytomegalovirus (CMV) is largely due to an increase in the number of cases of acquired immunodeficiency syndrome and organ transplantation in recent years. The proper recognition of CMV‐infected cells in gastrointestinal mucosal biopsies is critical for effective treatment of this condition.

Quantitative and Ultrastructural Analysis of Rectal Mucosal Mast Cells in Acute Infectious Diarrhea

The role of mast cells, potential mediators ofmucosal immunity and inflammation, was studiedmorphologically in the rectal mucosa in two acutediarrheal diseases, cholera and shigellosis.Quantitation of mucosal mast cells showed that they weresignificantly higher in the deeper lamina propria whereblood vessels and nerves were more abundant. There wasno difference in mast cell counts or degranulation in the mucosa in both groups of patients andcontrols. Intraepithelial mast cells were decreased inthe patients. The prevalence of lipid bodies wassignificantly higher in mast cells from patients with cholera and shigellosis (P < 0.01). Thesefindings suggest that mast cell populations are moredense around blood vessels and nerves and thatinflammatory mediators derived from arachidonic acidmetabolites, as indicated by the lipid bodies, are theresponse of mast cells to the alterations in diarrhea,despite differences in the etiology ofdiarrhea.

Prevalence of Helicobacter pylori in southern Indian controls and patients with gastroduodenal disease

Abstract The spiral organism Helicobacter pylori has been casually implicated in the genesis of various gastroduodenal diseases. Since these diseases are common in southern India, this study was undertaken to determine the prevalence of H. pylori in the gastric mucosa of asymptomatic adults and patients with various gastroduodenal diseases. H. pylori was detected in the gastric mucosa of 25 of 30 (83.3%) normal volunteers. Prevalence rates in the disease groups were also high, and included 38 of 41 patients with duodenal ulcer (92.6%), 13/16 with gastric ulcer (81.3%), and 85/119 subjects (71.4%) with non‐ulcer dyspepsia. Light microscopic examination of the gastric mucosa provided the best method of detecting H. pylori. H. pylori colonization was significantly associated with histological abnormalities, mainly chronic atrophic gastritis (147) and superficial gastritis (11), while only three of 161 H. pylori positive patients had histologically normal antral mucosa. Ultrastructural examination revealed changes in the apical complex of the gastric mucosal cells in response to bacterial adhesion, with mucus depletion and cellular damage. Bacteria were also noted disrupting the tight junctions and entering the intercellular spaces. The high prevalence of H. pylori infection may explain the high incidence of gastritis, duodenal ulceration and gastric carcinoma in this population. However, in this population, the prevalence of infection in asymptomatic individuals was nearly as high as that in duodenal ulcer, underlining the need for further study to identify the differences in host response or bacterial pathogenicity that lead to the development of ulcer in only some individuals.

A Monkey Model for Enterohemorrhagic Escherichia coli Infection

Adult Macaca radiata (n=22) were infected intragastrically with 10(12) Escherichia coli O157:H7 strain 84-01, which produces Shiga toxins 1 and 2. Clinical symptoms and bacterial excretion were documented in each monkey for a specified time period before they were killed. At necropsy, samples were obtained for culture and histologic and ultrastructural examination. Seventeen monkeys had diarrhea: E. coli O157 was isolated from postinfection stool samples from all monkeys and from autopsy cultures for 14 of 22 monkeys. Histologic examination showed attaching-effacing lesions, which appeared at 12 h and persisted for 7 days, in 12 monkeys. Widening of the intercellular spaces, degeneration and vacuolization of the epithelial cells, epithelial tufting, extrusion of epithelial cells, and neutrophilic infiltration were characteristic features seen in 20 of the 22 infected monkeys but not in 4 control monkeys. This monkey model closely parallels the early stages of the disease produced by E. coli O157:H7 and would be useful in the further study of pathogenic mechanisms and prevention methods in enterohemorrhagic E. coli infections.

Enteroaggregative Escherichia Coli infection in a rabbit model

Summary Type strains of enteroaggregative Escherichia coli EAEC (17‐2, serotype O3:H2; JM 221, serotype O92:H33), isolates from an adult and a child with diarrhoea and an asymptomatic colonised child were used to orally infect adult rabbits. The experimental animals were followed up and sacrificed at defined time periods. Colonisation of both small and large intestine was seen with all strains and isolates used. Isolates from an adult patient with diarrhoea (MP 27) and from an asymptomatic colonised child from the community (KM 1337) were recovered from the small intestine during the first week of infection and subsequently from the large intestine. A total of seven rabbits was infected with MP 27; while colonising the gastrointestinal tract of all seven rabbits, this isolate caused diarrhoea in only one. On ultrastructural examination, the rabbits infected with 17‐2 showed invasion of lymphoid follicles. Bacteria were seen in intercellular spaces and within M cells, a finding that has not previously been described. It is clearly possible to produce gut colonisation by oral infection with EAEC in adult rabbits with normal flora.

Epidemiological and laboratory investigations of outbreaks of diarrhoea in rural South India: implications for control of disease

Two epidemics of acute, watery diarrhoea in villages in North Arcot district, India, were investigated. The attack rates were 10.03 and 15.53 per 100 population, the median duration was 5 days and enteric pathogens were present in 56.8% and 60.3% of specimens from the two villages, but no predominant pathogen was identified. Examination of stools from a 20% age-stratified random sample of the population of one of the villages after the epidemic found 22.9% of asymptomatic subjects excreted bacterial enteric pathogens. Despite the high background of enteric pathogen carriage, the isolation rates for shigellae, enteropathogenic Escherichia coli and Shiga-toxin producing E. coli were significantly higher (P < 0.001, P < 0.02, P < 0.05) during the epidemic. The epidemics may have been caused by faecal contamination of well water following rain. Point-of-use techniques for water disinfection may be most effective for preventing such outbreaks, but further research into the development of appropriate technology is required.

Epithelial cell renewal and turnover and relationship to morphologic abnormalities in jejunal mucosa in tropical sprue

A morphometric study confirmed that increasing severity of the jejunal mucosal morphologic lesion is accompanied by increased crypt height and reduced villus length in patients with tropical sprue. Mitotic activity in the crypts was increased. Pulse labeling of jejunal mucosal biopsies culturedin vitro with [3H]thymidine confirmed that there was increased uptake of label in tropical sprue with more rapid migration of labeled cells to the villi. The label was also lost more rapidly. Earlier ultrastructural studies have shown enterocyte damage and extrusion in the crypt and villus epithelium. The present data suggest that in the jejunal mucosa of patients with tropical sprue, the loss of damaged enterocytes leads to villus shortening and increased cell production in the crypts, with hypertrophy of the crypts.