Selective criteria for the microbiological examination of faecal specimens.

To assess the effectiveness of predetermined investigation criteria for the examination of faecal samples from inpatients, cultured stool specimens were prospectively examined for Salmonella spp, Shigella spp, Campylobacter spp and Clostridium difficile, and screened microscopically for intestinal parasites. Out of a total of 505 specimens, 421 (83%) fulfilled the criteria for examination for C difficile, 254 (50%) for Salmonella spp, Shigella spp, and Campylobacter spp, and 87 (17%) for intestinal parasites. Isolation rates for these organisms in those groups of patients where examination was indicated were 22.5% for C difficile and 9.1% for Salmonella spp, Shigella spp, and Campylobacter spp; the detection rate for parasites was 3.5%. In those patients where the criteria did not suggest investigation, the isolation or detection rates were 3.6% for C difficile, 0% for Salmonella spp, Shigella spp, and Campylobacter spp, and 1.7% for intestinal parasites, suggesting that the use of predetermined investigation criteria was effective.