415 - Antibiotic Resistance and Molecular Epidemiology of Escherichia coli Isolates Producing Neonatal Bacteremia

A total of 93 neonates with E. coli bacteremia were retrospectively identified from two tertiary-care hospitals from 2006-2021. E. coli blood isolates, and clinical and antibiotic susceptibility data were obtained. Whole genome sequencing (WGS) was done on all isolates to determine their multi-locus sequence type (MLST) and the presence of K1 capsule encoding genes.

Results: Blood isolates were collected from n=93 neonates. There were no differences in the proportion of male vs. female newborns, or preterm vs. term status (Table 1). Birthweight (BW) was available in n=85 newborns; BW was significantly lower in preterm vs. term newborns (p< 0.001, t-test). CSF was collected in n=54 (58%) of all newborns, n=14 (26%) had meningitis. The proportion of meningitis was not different between preterm vs. term newborns. Among all 93 newborns, 17 died: n=15 were preterm vs. n=2 term (p< 0.001, Fisher exact test). Necrotizing enterocolitis was more frequent in preterm (n=14) vs. term (n=1) newborns (p< 0.001, Fisher exact test).  Only 20 newborns had a central line when blood culture was obtained. WGS showed multiple STs, of which ST 95 (n=19, 20%) was the most prevalent, followed by ST 131 (n=13, 14%), and ST 69 (n=8, 9%) (Table 2). The K1 capsule genes were present in n=38 (41%) of all bacteremia isolates and in n=9 (64%) of the 14 concomitant meningitis cases. Overall resistance to ampicillin was 60%, to gentamicin was 13% (all had concurrent resistance to ampicillin), and to ceftriaxone was 6%. Four percent of isolates produced extended-spectrum beta lactamases and 5% were multi-drug resistant. We found no carbapenem resistance. Of the 17 newborns who died, n=6 (35%) had isolates non-susceptible to both ampicillin and gentamicin.

Conclusion(s): Preterm infants continue to have a significantly higher mortality due to E. coli bacteremia compared to term infants. Prevalent antibiotic resistance in neonatal E. coli isolates remains a concern. Common genomic characteristics of neonatal E. coli invasive isolates need continued surveillance in order to better understand relevant pathogenicity determinants.