Abstract & Commentary
Changing Epidemiology of Bacteremia in Infants
By Hal B. Jenson, MD, FAAP, Dean, School of Medicine, Western Michigan University School of Medicine, Kalamazoo, MI., is Associate Editor for Infectious Disease Alert.
Dr. Jenson reports no financial relationships relevant to this field of study.
Source: Greenhow TL, Hung YY, Herz AM: Changing epidemiology of bacteremia in infants aged 1 week to 3 months. Pediatrics 2012;129:e590.
A retrospective analysis was conducted of all blood cultures collected on full-term (>=37 weeks) previously healthy infants presenting for care from 1 week to 3 months of age in a large California healthcare system over 5 years (2005-2009). Of the 4,255 blood cultures collected from 4,122 infants, among a cohort of 160,818 infants born in the system during that period, 2.2% (92) were positive for pathogens and 5.8% (247) were positive for contaminants. The most common pathogen was Escherichia coli (52 cases; 56%), which was associated with a urinary tract infection in all but a single case (98%). The next most common pathogens were Group B Streptococcus (19 cases; 21%) and Staphylococcus aureus (7 cases; 8%). Other gram-negative organisms included 2 cases each of Klebsiella and Salmonella, and 1 case each of Citrobacter and Moraxella. There were 3 cases of Streptococcus pneumoniae (none in the first month of life), 1 case each of Enterococcus and Group A Streptococcus, and no cases of Listeria monocytogenes nor Neisseria meningitidis.
Ampicillin resistant pathogens accounted for 33 of 92 (36%) organisms. Among the E. coli strains, 23 of 52 (44%) were resistant to ampicillin, 3 (6%) were resistant to gentamicin, and 1 (2%) was resistant to cefazolin. There were no strains of E. coli that were resistant to ceftriaxone. All of the strains of S. aureus were susceptible to methicillin.
Of the 92 infants with bacteremia, 6 (7%) had no documented fevers by parental history or at presentation. Sixteen (18.6%) of the infants were described as ill-appearing. Of the 10 infants with meningitis, 7 were ill appearing, and 1 was afebrile.
Bacteremia was slightly more likely from 7-28 days of age (2.84%) compared to 29-60 days (1.92%) and 61-92 days (2.14%), though these differences were not statistically significant. There were no trends in incidence. No predictor was statistically significant by multivariate analysis.
Commentary
Continuing the trend of other studies of the past decade on the epidemiology of bacteremia among infants, E. coli has replaced Group B Streptococcus as the leading cause of late-onset bacteremia in young infants. One limitation is that the design of this study included only full-term infants, and excluded premature newborns that are at higher risk of Group B Streptococcus infection. Despite this limitation, the results demonstrate the significant impact of recent changes in our management of perinatal maternal colonization. This healthcare system has very high rates of maternal screening for Group B Streptococcus and use of intrapartum antibiotics, which decrease vertical transmission of Group B Streptococcus. These changes in perinatal practices since recommendations were formalized in 1996 have significantly reduced the risk of neonatal Group B Streptococcus infections.
Ampicillin resistance was found in 36% of all cases, and in 44% of cases of E. coli bacteremia including the one case of E. coli meningitis. This underscores the importance of including third-generation cephalosporins as part of the empirical antibiotic regimen for management of fever and bacteremia in infants 1 week to 3 months of age.
A retrospective analysis was conducted of all blood cultures collected on full-term (>=37 weeks) previously healthy infants presenting for care from 1 week to 3 months of age in a large California healthcare system over 5 years (2005-2009).You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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