Risk factors associated with ampicillin-resistant infection in newborns in the era of group B streptococcal prophylaxis

Alison C. Rentz, Matthew H. Samore, Gregory J. Stoddard, Roger G. Faix, Carrie L. Byington

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Objectives: To document the trend of ampicillin-resistant infections in newborns weighing at least 1500 g and to determine factors associated with ampicillin-resistant neonatal early-onset infection in the era of routine group B streptococcal prophylaxis. Design: Case-control study. Setting: Referral hospital with level I through level III nurseries. Patients: Newborns aged 0 to 7 days with cultures positive for bacterial infection, born from January 1994 to August 2002 (n = 53). Random controls were matched to admission year and nursery level (n = 159). Main Outcome Measures: Trends of and factors associated with ampicillin-resistant infections. Results: Trends in our institution were the same as those found in some recent reports, a decrease in group B streptococcal early-onset infections without a concomitant increase in gram-negative early-onset infections. Specifically, when stratified by birth weight, newborns weighing at least 1500 g had no increase in gram-negative pathogens in the eras both before and after group B streptococcal prophylaxis (0.8 per 1000 live births to 0.3 per 1000 live births; incidence ratio, 2.3 [95% confidence interval, 0.5-10.9]). No increase in ampicillin resistance was seen during the same 3 periods (50%, 60%, and 50%, respectively; P = .97). Independent risk factors associated with ampicillin-resistant early-onset infection were intrapartum antibiotics for a 24-hour duration or longer (odds ratio, 4.8 [95% confidence interval, 1.0-23.3]) and clinical chorioamnionitis (odds ratio, 9.2 [95% confidence interval, 2.6-32.9]). Conclusions: No increase in early-onset infections with gram-negative or ampicillin-resistant pathogens was detected. Ampicillin-resistant early-onset infection was associated with intrapartum antibiotics given for 24 hours or longer prior to delivery and with clinical chorioamnionitis. Ampicillin sodium and gentamicin sulfate remain appropriate initial antibiotic therapies for early-onset infection in newborns weighing at least 1500 g and without these risk factors.

Original languageEnglish (US)
Pages (from-to)556-560
Number of pages5
JournalArchives of Pediatrics and Adolescent Medicine
Issue number6
StatePublished - Jun 2004

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health


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