A cluster of Listeria monocytogenes infections in hospitalized adults.

Background: Listeriosis occurs mainly in persons at extremes of age and with immunocompromising conditions. It is believed that most cases of listeriosis are acquired in the community. A cluster of listeriosis in hospitalized patients prompted the present investigation.

Methods: We conducted a case series study of listeriosis from August 21, 2006, to June 1, 2007, in a hospital in the city of Rio de Janeiro, Brazil.

Results: Six patients with Listeria monocytogenes infection were identified: 5 during hospitalization and 1 at a day clinic. By the time the infection was diagnosed, 5 patients had been in the hospital for a mean of 9 days. All patients were elderly (median age, 80 years) and had immunocompromising conditions. Five (83%) patients died. Four patients developed bloodstream infections, 3 caused by serotype 1/2b. Two patients had peritonitis: one caused by serotype 3b and another by serotype 1/2b. Four L monocytogenes isolates belonged to a single pulse-field gel electrophoresis genotype, suggesting a common source. An epidemiologic investigation pointed to the hospital kitchen as the possible contamination.

Conclusion: Data suggest a health care-associated outbreak of listeriosis and highlight the importance of developing guidelines for prevention and treatment of health care-associated foodborne diseases, especially in hospitals with immunocompromised adult patients.