[Opportunistic bacteria].

The definition of opportunistic bacteria is based on two parameters: the receptive subject and the bacteria. When the receptive subject is normal, theoretically, no saprophytic or normal commensal organisms are able to invade the subject. This subject can only be infected by certain "undesirable" commensal organisms such as Vargues' Specific Pathogenic Bacteria. If an otherwise normal subject has a temporary decrease in his immune defences, he may be invaded by a number of organisms from the normal commensal flora: these are the opportunistic bacteria in the broad sense of the term. The immunosuppressed patient with profound and prolonged depression of his immune system may be attacked by various saprophytic organisms and a number of commensal organisms, even those which were previously considered to be non-virulent. These are the opportunistic infections in the strict sense of the term.