Role of the microbiology laboratory in the diagnosis of nosocomial diarrhea.

Diarrhea that occurs in hospitalized patients is frequent and may be due to infectious or noninfectious causes. In adults with nosocomial diarrhea, th e most commonly detected agent is Clostridium difficile; in children, rotav iruses are predominant. Various studies have shown that bacterial enteric p athogens (e.g. Salmonella spp., Shigella spp., Campylobacter spp...) or par asites are common causes of community-acquired diarrhea but rarely cause no socomial enteritis. Stool cultures for these pathogens and ova and parasite examinations should not be performed in patients hospitalized for more tha n three days unless there are plausible clinical or epidemiological reasons to do so. In contrast, C. difficile toxins assay (and rotavirus screening in children) should be primarily requested. The detection of C. difficile t oxin B by stool cytotoxicity assay remains the 'gold standard'. Identificat ion of toxin A (or A+B) can also be performed by immuno-enzymatic (ELISA) t ests: results may be obtained in three hours. Electronic microscopy is the standard method for rotavirus diagnosis but tests using latex agglutination or immuno-enzymatic assay are now available. Various typing methods have b een developed and may be routinely used in epidemiological investigations. (C) 2000 Editions scientifiques et medicales Elsevier SAS.