Occult bacteremia from a pediatric emergency department: Current prevalence, time to detection, and outcome

Objective. To evaluate selected characteristics of occult bacteremia in the post-Haemophilus influenzae type b (HIB) vaccine era. Methods. A retrospective cohort study was performed involving 5901 children 2 to 24 months old with fever greater than or equal to 39.0 degrees C eval uated with a blood culture at an urban tertiary care children's hospital em ergency department (ED) between February 1993 and June 1996. Patients were excluded if immune-suppressed, diagnosed with a focal infection, evaluated by lumbar puncture, or admitted to the hospital during initial evaluation. Prevalence of occult bacteremia, distribution of current pathogenic organis ms, and time to positive culture in a continuously monitored system were de termined. All patients with cultures positive for pathogenic bacteria were reevaluated and serious adverse outcomes were documented. Results. The prevalence of occult bacteremia was 1.9% (95% confidence inter val: 1.5%-2.3%). Streptococcus pneumoniae accounted for 82.9% of all pathog ens and H influenzae was not a causative organism in this cohort. The mean time to positive culture was significantly shorter for pathogens c ompared with contaminants (14.9 hours vs 31.1 hours). A culture that was po sitive in less than or equal to 18 hours was 13.0 (6.3-26.6) times more lik ely to contain a pathogen than a contaminant. The average time from positive culture notification to reevaluation in the ED was 10.6 hours and over half of the patients recalled to the ED for posi tive cultures were admitted to the hospital. Of patients with occult pneumo coccal bacteremia, 95.7% had resolution of their bacteremia without the use of parenteral antibiotics. Two patients had serious adverse outcomes. The rate of meningitis or death was .03% (.004%-.12%). The contamination rate of blood cultures was 2.1% (1.7%-2.5%). Most (85%) o f these patients were reevaluated in the ED and more than one third were ad mitted to the hospital before full identification of the organism. Conclusions. Prevalence of occult bacteremia in the post-HIB vaccine era is lower than previously reported. S pneumoniae is the most common causative organism and resolves without parenteral antibiotics in the vast majority o f cases. Continuously monitoring blood culture systems allow for early iden tification and can aid in differentiating contaminated from true pathogenic cultures by time to positive culture. Serious adverse outcome is an uncomm on result of occult bacteremia. Updated epidemiology and microbiologic tech nology may impact the evaluation and treatment of children at risk for occu lt bacteremia.