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Lower than expected rates, different types of bacteremia in pediatric patients
Greenhow TL. Pediatrics. 2012;doi:10.1542/peds.2011-1546.
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The incidence of true bacteremia in 1-week to 3-month-old infants is infrequent, and this infrequency should prompt a change in how clinicians view presumptive antibiotic coverage, according to study results published online.
Tara L. Greenhow, MD, and colleagues looked retrospectively at blood cultures from healthy, full-term infants in need of care at Kaiser Permanente in Northern California from 2005 to 2009.
Of the 4,255 blood cultures, 2.2% were positive for pathogens vs. cultures positive due to contaminants. The most common pathogens found were Escherichia coli (56%), group B streptococcus (21%) and Staphylococcus aureus (8%). Greenhow and colleagues said 98% of infants with E. coli also had a urinary tract infection. No cases of Listeria monocytogenes bacteremia or meningococcemia were found; researchers found only one case of enterococcal bacteremia. The actual rate of bacteremia was 0.57 in 1,000 full-term births.
“Before this study, the incidence of late-onset bacteremia was unknown. Compared with CDC data, we have documented a lower incidence of group B streptococcus bacteremia,” the researchers wrote.
Incidence range before the study was reportedly 1.1% to 5.9%, and group B streptococcus was thought to be the most common pathogen, according to the researchers. The data indicated that 36% of pathogens were ampicillin resistant, which they suggested calls for a change in antibiotic treatment.
“On the basis of the pathogens found and antibiotic susceptibilities, we suggest new strategies are for presumptive treatment of bacteremia and question whether ampicillin still needs to be part of every empirical antibiotic regimen in infants 1 week to 3 months old,” the study researchers concluded.
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Samir S. Shah, MD, MSCE
The study by Greenhow and colleagues answers several important questions in the management of neonates and young infants with suspected bacterial infection but also raises additional questions regarding optimal treatment. This study provides current data on the incidence of late-onset bacteremia in infants. Late-onset bacteremia is defined as bacteremia occurring beyond the first week of life but within the first 3 months of life. Greenhow and colleagues also confirm prior studies demonstrating the rare occurrence of Listeria infection in this age group.
Ampicillin and gentamicin have historically been used for empiric treatment of young infants with suspected bacterial infection. Ampicillin, rather than third-generation cephalosporins such as cefotaxime. have been used to cover for the possibility of infection with Listeria monocytogenes and Enterococcus species, bacteria that are naturally resistant to cephalosporins. The rare occurrence of infections caused by these bacteria and the relatively high prevalence of ampicillin resistance among Escherichia coli, the most common pathogen identified, suggest that we ought to reconsider our approach to empiric antibiotic treatment of this population.
The major challenge here is that the association between discordant empiric antibiotic therapy, which occurs when the bacterium is resistant to the initial antibiotic regimen, and outcomes is poorly defined in the setting of urinary tract infections with concomitant bacteremia. However, given the potential negative consequences of discordant empiric therapy in neonates and young infants, the high prevalence of ampicillin resistance among E. coli, and the difficulty in accurately identifying all infants with meningitis at presentation suggest that we need to reconsider our traditional treatment strategies. The prevalence of antibiotic resistance varies geographically so it is important to know your local susceptibility patterns. The typical hospital antibiogram has potential to be misleading unless susceptibility results for community- and hospital-acquired infections are reported separately.
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