Nosocomial infection in the community hospital: severe infection due to Serratia species.

BACKGROUND: Serratia bacteremia is an uncommon illness in hospitalized patients. The aim of this study was to determine how frequently this disease occurs nosocomially and to discover the most common portals of entry and the underlying disorders.
METHODS: Fifty-six cases of Serratia bacteremia documented by blood culture (17 cases over a 4-year period in a community hospital in Gainesville, Florida, and 39 cases over a 3-year period in three community hospitals in Dayton, Ohio) were reviewed. Comparison was made with 60 control cases of general bacteremia from three Dayton hospitals.
RESULTS: Of the 56 study cases of Serratia bacteremia, 45 (80.4%) were classified as nosocomial, compared with 13 (21.7%) of the controls. Twenty-seven (48.2%) of the 56 Serratia cases occurred in intensive care units. The cases were evenly distributed over the two study periods, and no outbreaks on specific units were noted. The most common portals of entry for Serratia organisms were, in descending order, lung, genitourinary tract, unknown, intravenous line, gastrointestinal tract, and skin. The most common underlying disorder for Serratia bacteremia was malignancy, followed by renal failure (acute or chronic) and diabetes mellitus. Most of the Serratia organisms tested were sensitive to carbenicillin, trimethoprim/sulfamethoxazole, ceftizoxime, ceftriaxone, ceftazidime, cefotetan, aztreonam, ticarcillin/clavulanate, and ciprofloxacin. The organisms were largely resistant to ampicillin, tetracycline, cefazolin, cephalothin, and cefuroxime. Twenty-five percent of the patients with Serratia bacteremia died, compared with 13.6 of the bacteremic controls.
CONCLUSION: Serratia bacteremia is often acquired nosocomially. The mortality rate among the study population was surprisingly low for this opportunistic bacteremia, but was higher (though not significantly so) than that of the controls.