Blood culture and bacteremia predictors in infants less than three months of age with fever without source.

OBJECTIVES: (1) To assess the rate of bacteremia in febrile infants less than 3 months of age admitted to a pediatric emergency department at a tertiary hospital; (2) to describe the bacteria isolated; and (3) to analyze factors related to increased probability of having a positive blood culture.

METHODS: A retrospective, cross-sectional, 5-year descriptive study that includes all infants less than 3 months of age who presented with fever without source (FWS) and had a blood culture performed.

RESULTS: A blood culture was performed in 1018 (91.5%) of 1125 infants admitted, and a bacterial pathogen was grown in 23 (2.2%) of these; 8 were associated with a positive urine culture. The most frequently isolated pathogen was Escherichia coli (9), followed by Streptococcus pneumoniae (4). The risk factors detected by multivariate analysis were: (a) being classified as "not well-appearing" (12.5% vs. 1.8%; odds ratio: 8.37) and (b) leukocyturia and/or nitrituria in a urine dipstick test (5.6% vs. 1.6%; odds ratio: 3.73). C-reactive protein value was higher than white blood cell count and absolute neutrophil count in detecting bacteremia; a 70 g/L cut-off had a specificity of 93.8%, but sensitivity of only 69.6%.

CONCLUSIONS: A positive blood culture rate of 2.2% was found in infants less than 3 months of age with FWS. C-reactive protein, white blood cell count, and absolute neutrophil count were not good bacteremia predictors. We recommend obtaining a blood culture in infants less than 3 months of age with FWS, particularly those patients considered "not well-appearing" and those with leukocyturia and/or nitrituria.