Patients were asked to provide a stool sample for microbiological evaluation. For each questionnaire and corresponding stool sample, the same anonymous identification number was issued in order to match laboratory results. In addition, a case-crossover study was conducted to identify determinants of diarrhea during
the military deployment. This design is Y-27632 manufacturer equivalent to a case–control study in which patients serve as their own controls with data used from different points of time.6 The case-crossover method controls all confounding factors such as sex, age, or susceptibility to diarrhea, thus making it possible to consider only changes in behaviors. The case-crossover design was performed under the assumption that the incubation period of most of the pathogens was rarely higher than 3 days.7 The high-risk period for exposure was thus the 3 days immediately preceding the onset of diarrhea symptoms. The control period was the same 3 days of the previous week (Figure 1). This design led us to exclude from the case-crossover analysis any diarrheal episodes occurring before the completion of
at least 10 consecutive days of stay in N’Djamena or in the 10 days following a previous diarrheic episode. The behaviors assessed were places to eat (official mess in the French military camp in N’Djamena, local restaurants, temporary encampments, and field kitchens), ice in drinks, hand washing before eating, eating unpeeled fruit or vegetables, and close contact with other patients with diarrhea. The first step of laboratory diagnosis Microtubule Associated inhibitor was performed in high throughput screening compounds the military camp in the field laboratory facility and consisted of direct microscopic examination of fresh fecal smears for parasites and bacterial analyses. Stool samples were also cultured using standard procedures for Salmonella spp and Shigella spp (Salmonella–Shigella agar). Then, stool samples were aliquoted and stored at −80°C before complementary microbial investigations in the Laboratory of the Val de Grâce Hospital, Paris, France. Here, samples were cultured for Salmonella, Shigella, Campylobacter, Escherichia
coli, and Staphylococcus aureus. For Campylobacter, direct antigenic immunoenzymatic assay was also performed (Ridascreen Campylobacter Elisa, R-Biopharm AG, Darmstadt, Germany). Calicivirus (norovirus) and Astrovirus were both detected by two methods: ELISA immune-enzymatic techniques, (Ridascreen Norovirus, R-Biopharm AG; IDEIA Astrovirus, Oxoid, Ely, UK), and molecular tools using RT–PCR (Calici/Astrovirus Consensus, Argene-Biosoft, Varilhes, France). Finally, stool samples were examined for rotavirus (Ridascreen Rotavirus, R-Biopharm AG) and adenovirus 40–41 (IDEIA Adenovirus, Oxoid). The mean number of soldiers based in N’Djamena during the study period (exposed population) was used as denominator for the global incidence rate calculation (n = 1,024 for 5 months).