Intrapartum antibiotic prophylaxis 1: relative effects of recommended antibiotics on gram-negative pathogens.

OBJECTIVE

To assess whether the antibiotic chosen for intrapartum antibiotic prophylaxis affects the subsequent exposure of the neonate to ampicillin-resistant gram-negative bacteria.

METHODS

We performed a randomized clinical trial of ampicillin versus penicillin for intrapartum antibiotic prophylaxis. Genital tract cultures for Enterobacteriaceae were obtained at study entry and 8-36 hours postpartum. Organisms were isolated, identified, and tested for ampicillin susceptibility.

RESULTS

The ampicillin (n = 175) and penicillin (n = 177) groups, respectively, did not differ in rates of ampicillin-resistant Escherichia coli at entry (25% versus 22%, P =.57) or postpartum (36% versus 38%, P =.64). Similarly, groups did not differ in rates of ampicillin-resistant Enterobacteriaceae at entry (38% versus 32%, P =.23) or postpartum (51% versus 55%, P =.46). However, postpartum culture rates of resistant Escherichia coli were higher than entry culture rates for both the ampicillin (36% versus 25%, P =.026) and penicillin (38% versus 22%, P <.001) groups. Postpartum culture rates of resistant Enterobacteriaceae were also higher than entry culture rates for both the ampicillin (51% versus 38%, P <.001) and penicillin (55% versus 32%, P <.001) groups. Results were similar when considering only women who received two or more doses and no additional antibiotics.

CONCLUSION

Intrapartum antibiotic prophylaxis with either ampicillin or penicillin increases exposure of neonates to ampicillin-resistant Enterobacteriaceae.