Clostridium perfringens as a cause of infectious endocarditis in a patient with a vascular prosthesis.

mission by breast milk and sexual transmission are no longer risk factors for this population. Moreover, drug abuse and sexual promiscuity are rare in the Mashhadi population because these individuals are brought up in Orthodox Jewish households. A possible explanation for the rise in the seroprevalence of HTLV-I infection is that individuals may be exposed to an agent of low virulence over their lifetimes, possibly by coming in contact with salivary secretions (HTLV-I has been detected in saliva) [9, 10]. The age-dependent increase in the incidence of HTLV-I infection may suggest that horizontal transmission is predominant in populations such as the Mashhadi and that transmission via salivary secretions may be a significant factor. Our results support the possibility that HTLV-I is a dormant infection and that detection of antibodies is delayed as the rate of infection increases with age. This increase can be explained by the fact that the elderly have increased susceptibility to infections because of changes in lifestyle and nutrition or because of a decrease in immunologic functions. These factors as well as poor oral hygiene (which is common among the elderly) may contribute to cross-infectivity of HTLVI through the salivary route.