Clinical importance of polymicrobial bacteremia

Ninety-one episodes of polymicrobial bacteremia and fungemia were compared with 407 unimicrobial episodes to assess differences in the microbiological, epidemiological, and clinical features of the two syndromes. Enterobacteriaceae, nongroup A streptococci, anaerobic bacteria, and pseudomonads were disproportionately common in polymicrobial bacteremia. Polymicrobial episodes were significantly more likely to be hospital-acquired, to emanate from bowel or multiple foci, and to occur in patients with nonhematologic malignancies or multiple underlying diseases. Deaths directly related to sepsis were twofold higher in polymicrobial versus unimicrobial bacteremia. Factors associated with increased mortality in polymicrobial sepsis included age greater than 40 yr; absent or diminished febrile response to sepsis; absolute granulocytopenia; inadequate antimicrobial therapy for all microorganisms isolated; and a primary focus of infection in the bowel, the respiratory tract, an abscess, or an occult site. The occurrence and type of polymicrobial bacteremia can suggest a source of sepsis as well as additional diagnostic and therapeutic maneuvers.