Neonatal early onset Escherichia coli sepsis: trends in incidence and antimicrobial resistance in the era of intrapartum antimicrobial prophylaxis.

BACKGROUND: Although intrapartum antimicrobial prophylaxis has lowered the incidence of early onset group B Streptococcus (GBS) sepsis, there are concerns that the increased use of antibiotics may raise the incidence of non-GBS antimicrobial-resistant infections. The objective of this study was to determine trends in the incidence and antimicrobial resistance of early onset sepsis caused by Escherichia coli in the era of antimicrobial prophylaxis.

METHODS: All neonates with early onset E. coli infection who were born at La Paz Hospital, Madrid, from January 1, 1992, through December 31, 2002, were identified from a microbiologic register of all neonatal infections. To evaluate the effect of the guidelines for GBS prevention, data were pooled and compared for: 1992 through 1995 (Period 1); 1996 through 1998 (Period 2); and 1999 through 2002 (Period 3).

RESULTS: Early onset E. coli infection was diagnosed in 41 of 84 612 live births. The infection rate did not change significantly during the 3 time periods (0.56, 0.24 and 0.55 per 1000 during Periods 1, 2 and 3, respectively; P = 0.936, linear-by-linear association). The proportion of E. coli infections that were resistant to ampicillin increased significantly among preterm infants, from 25% (1 of 4) in Period 1, to 100% (2 of 2) in Period 2 and to 91% (10 of 11) in Period 3 (P = 0.017, linear-by-linear association), but not among term infants, with 67% (8 of 12) in Period 1, 50% (1 of 2) in Period 2 and 44% (4 of 5) in Period 3 (P = 0.317, linear-by-linear association).

CONCLUSIONS: Although the incidence of early onset sepsis caused by E. coli remained stable during the study period, antibiotic-resistant E. coli infections increased among preterm infants. On the whole these trends are reassuring with respect to GBS prophylaxis. However, the increase in the proportion of ampicillin-resistant infections in preterm infants suggests that continuing evaluation of the risks and benefits of prophylaxis in this group is critical.