Shift seen in epidemiology of bacteremia in term infants

Escherichia coli has replaced group B Streptococcus (GBS) as the leading cause of bacteremia in term infants, with E coli accounting for 56% of cases, followed by GBS (21%) and Staphylococcus aureus (8%). This was the finding of a retrospective analysis of 4,255 blood cultures collected at Kaiser Permanente Northern California from 2005 through 2009 on full-term, previously healthy infants aged 1 week to 3 months brought in for care and for whom a blood culture was drawn.

Only 92 (2.2%) of all blood cultures were positive for pathogens, making the incidence rate of bacteremia 0.57 in 1,000 full-term births. However, another 247 cultures were positive because of contaminants, found most often in cultures obtained from the ED.

Gram-negative organisms accounted for most of bacterial pathogens; in addition to E coli, present in the cultures of 52 of the 92 infants with bacteremia, Klebsiella sp or salmonella sp were in the cultures of 2 infants, and Citrobacter sp or Moraxella were in 1 infant each.

Ampicillin-resistant pathogens accounted for 36% of organisms, and no cases of methicillin-resistant S aureus were seen (Greenhow TL, et al. Pediatrics. 2012;129[3]:e590-e596).

Commentary

This study is based on a very large sample collected by Kaiser Permanente of Northern California. The researchers point out that the represented population probably had access to good prenatal care with maternal GBS screening and perinatal antibiotic therapy if indicated. So, GBS may be underrepresented here compared with the general population. If that's the case, the study is an endorsement of careful obstetric screening and treatment for this organism. The researchers also point out the absence of any blood cultures positive for Listeria monocytogenes and propose that it may be time to give up on including ampicillin in initial empiric therapy for young febrile infants. I am not ready for that change. Listeria has never been common, but it still worries me. -Michael Burke, MD

DR BURKE, section editor for Journal Club, is chairman of the Department of Pediatrics at Saint Agnes Hospital, Baltimore, Maryland. He is a contributing editor for Contemporary Pediatrics. He has nothing to disclose in regard to affiliations with or financial interests in any organization that may have an interest in any part of this article.