POTENTIAL CONSEQUENCES OF WIDESPREAD ANTEPARTAL USE OF AMPICILLIN

OBJECTIVE: Recommendations for the use of antenatal antibiotics in obs tetrics have increased in the past few years, especially for prophylax is against group B streptococci, for prolongation of the latency time in patients with preterm premature rupture of the membranes, and as an adjuvant treatment in preterm labor. Our objective was to determine w hether the use of antenatal ampicillin affects the incidence of and re sistance of early-onset neonatal sepsis with organisms other than grou p B streptococci. STUDY DESIGN: A prospective cohort study was perform ed between January 1, 1991, and December 31, 1996. Every case of blood culture-proven neonatal sepsis was prospectively surveyed. The type o f bacteria isolated, drug resistance, antenatal antibiotic use and tre atment indication, gestational age at delivery, and other antenatal an d outcome variables were gathered. Early-onset neonatal sepsis was def ined as disease onset within 7 days after birth. RESULTS: A total of 4 2 cases of early-onset neonatal sepsis among 29,897 neonates delivered were found during the 6-year period. Of these, 15 cases were due to g roup B streptococci and 27 were the result of non-group B streptococca l organisms (21 gram-negative rods and 6 gram-positive cocci). Among t he 27 non-group B streptococcal cases, 15 mothers had received antenat al ampicillin and 13 of the 15 bacterial isolates from these neonates (87%) were resistant to ampicillin, versus only 2 ampicillin-resistant isolates (17%) among the 12 cases in which no antenatal antibiotics w ere administered (P = .0004). Of the 15 mothers who were treated with ampicillin, 13 received more than 1 dose. In evaluating each year of t he study, the overall administration of antibiotics to pregnant women in the antenatal period increased from <10% in 1991 to 16.9% in 1996. The incidence of early-onset neonatal sepsis with group B streptococci decreased during this time, whereas the incidence of early-onset seps is with non-group B streptococcal organisms, especially Escherichia co li, increased. CONCLUSIONS: The increased administration of antenatal ampicillin to pregnant women may be responsible for the increased inci dence of early-onset neonatal sepsis with non-group B streptococcal or ganisms that are resistant to ampicillin. At this time penicillin G, r ather than ampicillin, is therefore recommended for prophylaxis agains t group B streptococci. In addition, future studies are needed to dete rmine whether alternate approaches, such as immunotherapy or vaginal w ashing, could be of benefit.