[Implications of bacterial protein toxins in infectious and food-borne diseases]

Among the 315 protein toxins elicited by gram positive and gram negative bacteria so far characterized, about 50 toxins are currently considered as totally or partially, responsible of the pathological manifestations and/or lethality resulting from host infection or intoxication (contaminated food) by relevant toxinogenic bacteria. A certain number of criteria are required for the assessment of indisputable involvement of a toxin or an array of toxins (from the same bacteria) in infectious diseases: 1) The bacterial microorganism clearly identified as the pathogenic agent of the disease produces component(s) considered as toxin(s); 2) The administration to appropriate animal(s) of the toxin(s) separated from the relevant bacteria or produced by genetic engineering from a heterologous tox+ recombinant bacterial strain produces symptoms and pathophysiological disorders that mimic those observed in the natural disease or at least those elicited in experimental animals by the cognate toxin-producing bacteria; 3) The in vitro incubation of the isolated toxin(s) with appropriate animal organs, tissues or cells elicits certain pathophysiological, biochemical or metabolic manifestions observed in the host infected with the relevant toxinogenic bacteria; 4) Toxin concentration in the organism of the host infected by the toxinogenic bacteria should be compatible with the characteristics of the relevant disease. The toxins of pathogenic interest exhibit a variety of effects in bacterial diseases. Bacteria that colonize a wound or mucosal surface but do not invade target cells can produce toxins that act locally or enter the bloodstream and attack internal organs (e.g. Corynebacterium diphtheriae, Vibrio cholerae, ...). Bacteria growing in a wound can produce toxins that destroy host tissue and kill phagocytes in the immediate vicinity of the bacteria, thus facilitating bacterial growth and spread. On the basis of the above mentioned criteria, the following bacterial diseases among many others are toxin-associated (toxinoses): diphtheria, tetanus, botulism, whooping cough, diarrhea, bloody diarrhea, hemolytic uremic syndrome, cholera, scarlet fever, toxic shock syndrome, gas gangrene, B. fragilis diarrhea, anthrax, pseudomembranous colitis.