Effects of antenatal antibiotics on the incidence and bacteriological profile of early-onset neonatal sepsis. A retrospective study over five years.

Recommendations for the use of antenatal antibiotics have been widely implemented in the past few years, notably to prevent group B streptococcal disease or to prolong pregnancy in the case of preterm premature rupture of the membranes. We designed a retrospective study to assess the potential effects of this increasing use of antibiotics on the incidence and bacteriological profile of early-onset neonatal sepsis (EONS). All neonates referred to our department for suspected EONS from January 1 1995 through December 31 1999 were included. Antenatal antibiotic exposure together with clinical and microbiological data from the neonatal period were gathered and analyzed on a yearly basis. Of the 485 newborns who met the inclusion criteria, there were 101 cases of culture-confirmed sepsis; 339 cases of suspected sepsis and 69 cases of confirmed sepsis involved children born in the hospital, among a total of 16,627 live births registered in our center over the study period. The overall incidence of EONS dropped from 6.8 to 0.6/1,000 births between 1995 and 1999 (p < 0.001), but the rate of group B streptococcal infection decreased much more rapidly than that of non-group B streptococcal infection. We observed a trend towards the emergence of ampicillin-resistant Escherichia coli strains, which were isolated in seven cases. Among E. COLI infections, ampicillin resistance was statistically linked with antenatal antibiotic use (p = 0.025). We also delineated several risk factors associated with these infections. In our center, antenatal antibiotic treatment was effective in reducing the incidence of EONS, but this benefit may come at the cost of favoring the emergence of ampicillin-resistant organisms causing severe neonatal infections. Antenatal and postnatal antibiotic treatment strategies should take this adverse effect into account.