Clinical question: What is the epidemiology of bacteremia in one-week to three-month-old infants?
Background: Large studies of bacteremia in infants <90 days of age were largely performed before the era of routine prenatal screening and prophylaxis for Group B Streptococcus (GBS). Additionally, these studies have focused on febrile infants, which might not allow for characterization of the incidence of bacteremia when nonfebrile infants are considered.
Study design: Retrospective review.
Setting: Large HMO database.
Synopsis: Of 160,818 full-term infants born at Kaiser Permanente Northern California from 2005 to 2009, 4,255 blood cultures were obtained from 4,122 infants in outpatient clinics, the ED, or in an inpatient setting within 24 hours of birth. Preterm infants <37 weeks, infants with underlying medical conditions, and infants with cultures drawn within three days of an original culture were excluded.
A total of 8% of the blood cultures were positive, with 2.2% deemed true positives and 5.8% due to contaminants. The incidence rate of true bacteremia was 0.57 per 1,000 full-term births, with gram-negative organisms (predominantly Escherichia coli) representing the majority (63%) of pathogens, followed by GBS (21%), Staphylococcus aureus (8%), and Streptococcus pneumoniae (3%). There were no cases of Listeria monocytogenes or Neisseria meningitidis bacteremia, and there was one case of enterococcal bacteremia. Fever was absent in 7% of cases.
The authors conclude that ampicillin may no longer be necessary for empiric antibiotic coverage in this age group given that 36% of pathogens were resistant to ampicillin, there were no cases of Listeria, and there was only one case of enterococcus. However, these recommendations should be considered in light of the specific study setting, and might not be applicable to all areas.
Bottom line: E. coli, GBS, and S. aureus, in that order, are the most common causes of bacteremia in infants aged one week to three months.
Citation: Greenhow TL, Hung YY, Herz AM. Changing epidemiology of bacteremia in infants aged 1 week to 3 months. Pediatrics. 2012;129(3):e590-e596.
Reviewed by Pediatric Editor Mark Shen, MD, SFHM, medical director of hospital medicine at Dell Children's Medical Center, Austin, Texas.