An increased frequency of nontyphoidal
salmonellosis is well established in
cancer patients, but it is unclear whether this represents increased susceptibility to exogenous
infection or opportunistic, endogenous reactivation of asymptomatic carriage. In a retrospective study, a simple case definition was used to identify the probable presence of reactivation
salmonellosis in five
cancer patients between 1996 and 2002. Reactivation
salmonellosis was defined as the development of nosocomial
diarrhea >72 h after admission and following the administration of
antineoplastic chemotherapy in an HIV-seronegative
cancer patient who was asymptomatic on admission, in the absence of epidemiological evidence of a nosocomial outbreak. Primary
salmonellosis associated with unrecognized nosocomial transmission or community acquisition and an unusually prolonged incubation period could not entirely be ruled out. During the same time period, another
opportunistic infection,
Pneumocystis pneumonia, was diagnosed in six
cancer patients. Presumably, asymptomatic intestinal Salmonella colonization was converted to invasive
infection by
chemotherapy-associated intestinal mucosal damage and altered innate immune mechanisms. According to published guidelines, stool specimens from patients hospitalized for longer than 72 h should be rejected unless the patient is neutropenic or >or=65 years old with significant comorbidity. However, in this study
neutropenia was present in only one patient, and four patients were <65 years old. Guidelines should thus be revised in order not to reject stool culture specimens from such patients. In
cancer patients, nosocomial
salmonellosis can occur as a
chemotherapy-triggered opportunistic
reactivation infection that may be similar in frequency to
Pneumocystis pneumonia.