Polymicrobial bloodstream infection in pediatric patients: risk factors, microbiology, and antimicrobial management

Few studies focus on polymicrobial bloodstream infections (PBSIs) in children. In previous reports, children with PBSI frequently had complex underlying medical conditions and a high incidence of specific microorganisms, but systematic evaluation with controls was not performed. We postulated that specific clinical risk factors are associated with an increased risk of PBSI, and that illness may be more severe with these infections. Additionally, we suspected that routine empiric antimicrobial therapy may frequently be inadequate to treat the variety of pathogens in PBSI.

Positive blood cultures from 1998 to 2004 were reviewed. Patients whose cultures grew >1 organism were age-matched with monomicrobial bloodstream infection controls. Records were reviewed to compare their underlying medical conditions, organisms isolated, adequacy of therapy, and clinical characteristics of illness.

Twenty-nine episodes of PBSI were identified in 18 subjects. PBSI patients were more likely to have chronic medical conditions, chronic gastrointestinal pathology, central venous catheters, and to be receiving parenteral nutrition than controls. Pathogens found more commonly in PBSI episodes included Enterococcus spp., coagulase-negative staphylococci, and Candida spp. Empiric antimicrobial therapy was less likely to be adequate in patients with PBSI. PBSI patients were hospitalized longer, required longer intensive care and had prolonged bloodstream infection. Subjects with PBSI had prolonged duration of fever and had higher degrees of sepsis than controls.

Chronic medical conditions, particularly gastrointestinal disease, are risk factors for PBSIs. Because clinical illness may be more severe, alteration of the empiric antimicrobial regimen should be considered in some of these patients.