BackgroundDiarrheal diseases continue to contribute significantly to morbidity and mortality in infants and young children in developing countries. There is an urgent need to better understand the contributions of novel, potentially uncultured, diarrheal pathogens to severe diarrheal disease, as well as distortions in normal gut microbiota composition that might facilitate severe disease.ResultsWe use high throughput 16S rRNA gene sequencing to compare fecal microbiota composition in children under five years of age who have been diagnosed with moderate to severe diarrhea (MSD) with the microbiota from diarrhea-free controls. Our study includes 992 children from four low-income countries in West and East Africa, and Southeast Asia. Known pathogens, as well as bacteria currently not considered as important diarrhea-causing pathogens, are positively associated with MSD, and these include Escherichia/Shigella, and Granulicatella species, and Streptococcus mitis/pneumoniae groups. In both cases and controls, there tend to be distinct negative correlations between facultative anaerobic lineages and obligate anaerobic lineages. Overall genus-level microbiota composition exhibit a shift in controls from low to high levels of Prevotella and in MSD cases from high to low levels of Escherichia/Shigella in younger versus older children; however, there was significant variation among many genera by both site and age.ConclusionsOur findings expand the current understanding of microbiota-associated diarrhea pathogenicity in young children from developing countries. Our findings are necessarily based on correlative analyses and must be further validated through epidemiological and molecular techniques.

Typhoid fever is more common than paratyphoid fever in the urban Bangladeshi slum; children<5 years old have the highest incidence. Multidrug resistance is common in S. Typhi isolates and is associated with prolonged illness. Strategies for typhoid fever prevention in children aged<5 years in Bangladesh, including immunization, are needed.

We collected acute-phase serum samples from febrile patients at 2 major hospitals in Dhaka, Bangladesh, during an outbreak of dengue fever in 2001. A total of 18% of dengue-negative patients tested positive for leptospirosis. The case-fatality rate among leptospirosis patients (5%) was higher than among dengue fever patients (1.2%).

Hafnia alvei, a member of the family Enterobacteriaceae, was the only species of bacteria cultured from the stool of a 9-month-old child who was admitted with a 3-day history of watery diarrhea. The isolated strain of H. alvei failed to produce heat-labile or heat-stable enterotoxins or Shiga-like toxin I or II and did not invade HeLa cells, nor did it cause keratoconjunctivitis (determined by the Sereny test) in a guinea pig's eye. The strain, however, induced diarrhea in 8 of 12 adult rabbits with removable intestinal ties (removable intestinal tie-adult rabbit diarrhea [RITARD] assay) and in 1 of 2 orally fed animals. No diarrhea could be induced with Escherichia coli K-12 in eight RITARD assay rabbits and three orally fed rabbits, respectively. Microscopic examination of affected animals revealed moderate inflammatory cellular infiltration of the intestinal mucosa, in which bacterial attachment to the surface epithelium and loss of the microvillus border were evident in the ileum and colon. Electron microscopy demonstrated cellular modifications of the apical surface, with cupping or pedestal formation and increased terminal web density at sites of bacterial "attachment-effacement," a well-known characteristic and mechanism of diarrhea of enteropathogenic E. coli. Identical lesions were also induced by H. alvei in rabbit ileal loops, which ruled out naturally occurring rabbit enteropathogenic E. coli strains, which are known to produce similar lesions. It is concluded that at least some strains of H. alvei have the potential to cause diarrhea and that attachment-effacement is a virulence characteristic shared by bacteria other than E. coli.

We systematically investigated risk factors for typhoid fever in Kamalapur, a poor urban area of Bangladesh, to inform targeted public health measures for its control. We interviewed patients with typhoid fever and two age-matched controls per case about exposures during the 14 days before the onset of illness. The municipal water supply was used by all 41 cases and 81of 82 controls. In multivariate analysis, drinking unboiled water at home was a significant risk factor [adjusted odds ratio (aOR) 12.1, 95% CI 2.2-65.6]. Twenty-three (56%) cases and 21 (26%) controls reported that water from the primary source was foul-smelling (aOR 7.4, 95% CI 2.1-25.4). Eating papaya was associated with illness (aOR 5.2, 95% CI 1.2-22.2). Using a latrine for defecation was significantly protective (aOR 0.1, 95% CI 0.02-0.9). Improved chlorination of the municipal water supply or disinfecting drinking water at the household level may dramatically reduce the risk of typhoid fever in Kamalapur. The protective effect of using latrines, particularly among young children, should be investigated further.