[Nosocomial bacteremia caused by Serratia marcescens: analysis of 44 cases]

We have evaluated 44 cases of Serratia marcescens bacteremia (SB). Most took place in surgical services (57%) and the ICU (34%). In one occasion, the cases developed as an epidemic outbreak. SB basically developed in patients with underlying diseases (neoplasia in 32%, heart disease in 16%, chronic bronchitis in 14% and miscellaneous in 20%) in whom some invasive procedure had been carried out (98%). The most common complication was septic shock. In 17 cases the infection was polymicrobial. The most common serogroup was 0:5 (41%). 98% of strains were resistant to cephalothin, 78% to ampicillin and 29% to tobramycin. The mortality rate was 39% and the most common cause of death was septic shock. The factors which adversely influenced prognosis were as follows, in order of decreasing importance: leukocytosis, thrombopenia, associated gram-positive infection, age older than 65 years, "non-typable" serogroup, unknown portal of entry, epidemic case and septic shock.