Neonatal escherichia coli infections: concerns regarding resistance to current therapy

Currently recommended antibiotic treatment of suspected neonatal sepsis is ampicillin and an aminoglycoside. Recently, we observed increasing ampicillin and gentamicin resistance in strains of Escherichia coli isolated from neonates at our institution. We therefore reviewed clinical and laboratory records of all neonates with systemic infection, hospitalized from 1994 through 1998, from whom E. coli was isolated from blood and/or cerebrospinal fluid. The influence of perinatal variables (e.g. rupture of foetal membranes > 24h, group B Streptococcus (GBS) colonization, urinary tract infection during pregnancy and the use of antepartum and/or intrapartum antibiotics), and neonatal variables (e.g. gestational age, age at onset of sepsis (early: < or = 72 h, late: >72 h), number of E. coli septic recurrences, and associated underlying medical and/or surgical conditions) on antimicrobial susceptibilities of invasive E. coli isolates was studied. Twenty-three neonates with invasive E. coli infection were identified; most [19 (83%)] presented as late-onset sepsis (LOS). Ampicillin-resistant E. coli were isolated in 75% and 53% of neonates in the early- and late-onset groups, respectively. Gentamicin resistance was found in 50% of early-onset sepsis (EOS) isolates compared with 16% in the late-onset group. Isolates from two neonates with EOS were resistant to both ampicillin and gentamicin. One neonate with EOS and three with LOS had recurrent E. coli sepsis; all isolates were ampicillin-resistant and one was gentamicin-resistant. All these neonates were initially treated with ampicillin and gentamicin. Both groups had associated underlying medical and/or surgical conditions (50% early-onset, 47% late-onset). Maternal GBS colonization occurred in 2 (50%) versus 3 (16%) of EOS and LOS cases, respectively. All GBS colonized women received intrapartum ampicillin prior to delivery.

Ampicillin and gentamicin resistance is emerging in neonatal E. coli isolates from invasive infection. Current- empiric management of neonatal sepsis requires re-evaluation given changing antimicrobial susceptibilities.