Correlation of bacterial type and antibiotic sensitivity with maternal antibiotic exposure in early-onset neonatal sepsis

Background: Antibiotic administration during pregnancy as group B Streptococcus prophylaxis or as treatment of maternal conditions has become widespread. Objective: To assess whether bacterial type and antibiotic resistance in early-onset neonatal sepsis are associated with maternal antibiotic use. Methods: All positive blood and/or cerebrospinal fluid cultures (case-only study) and respective antibiotic sensitivities from newborns delivered in Shaare Zedek Medical Center, Jerusalem, Israel, between 01/01/1997 and 31/01/2007, taken during the first 72 h of life, were studied. Clinical and demographic data were obtained from the medical records of the infant/mother dyads. Three groups were defined by type of maternal antibiotic exposure: (1) no exposure, (2) intrapartum antibiotic prophylaxis (IAP), (3) antepartum antibiotic exposure during the month prior to delivery and extending into delivery or with subsequent IAP (AAE). Factors potentially associated with Gram-negative bacteremia and resistance to ampicillin were analyzed using multivariate logistic regression. Results: Ninety-seven different organisms grew from 94 infants (1.03 per 1,000 live births). By univariate analysis, AAE, gestational age ≤32 weeks, chorioamnionitis and rupture of membranes ≥18 h, were significantly associated with both Gram-negative sepsis and antibiotic resistance. By multivariate analysis, AAE was significantly associated with both outcomes, while gestational age ≤32 weeks was only associated with antibiotic resistance. Conclusions: AAE for more than 24 h is associated with an increased proportion of Gram-negative organisms and ampicillin resistance in early-onset neonatal sepsis. Antepartum antibiotic therapy and its ramifications need to be continuously monitored and prospectively studied.