[Infectious diarrhea in the adult]

Infectious diarrhoeas are usually divided into two types; toxinogenic and invasive. Invasive diarrhoeas are copious and responsible for dehydration which is the principal clinical sign; mucosal lesions and bacteraemia are absent. The most typical of toxinogenic diarrhoeas is cholera, but enterotoxicogenic E. coli and Aeromonas infections have similar clinical features. In invasive diarrhoeas the responsible microorganisms penetrate into the epithelial cells of the intestine, producing fever and stools that contain blood and mucus. However, some organisms causing invasive diarrhoeas secrete cytotoxins; they include Shigella spp., Salmonella spp, some strains of E. coli, Campylobacter jejuni and Yersinia spp. When diarrhoea occurs in patients under antibiotics pseudomembranous colitis due to the proliferation of Clostridium difficile must be suspected; the diagnosis is suggested by endoscopy and confirmed by bacteriology. Toxic and infectious diarrhoeas due to food are increasingly frequent; they are usually caused by Salmonella spp., but sometimes by Clostridium perfringens or Staphylococcus aureus. In patients with suspected infectious diarrhoea symptomatic treatment combined or not with intestinal antibacterial agents is immediately initiated in most cases; stool cultures are reserved to severe or protracted diarrhoeas. Specimens must be collected under the best conditions and rapidly sent to the laboratory.