Abstract
BACKGROUND: This study sought to investigate associations between virulence factors and phylogeny in all neonatal Escherichia coli bloodstream infections from patients admitted to the neonatal intensive care unit at Uppsala University Hospital between 2005 and 2020. METHODS: A total of 37 E. coli isolates from 32 neonates were whole-genome sequenced and analyzed for virulence factors related to extraintestinal E. coli; patient-related data were collected retrospectively from the medical records. RESULTS: E. coli isolates that belong to phylogroup B2 were associated with mortality (odds ratio [OR], 26; P < .001), extreme prematurity with delivery before gestational week 28 (OR, 9; P < .05), and shock (OR, 9; P < .05) compared with isolates of non-B2 group. Female neonates were more often infected with isolates of phylogroup B2 E. coli compared with male neonates (OR, 7; P = .05). The identification of the genotoxin determinant clb coding for colibactin exhibited strong associations with mortality (OR, 67; P < .005), gestational age (OR, 18; P < .005), and shock (OR, 26; P < .005). DISCUSSION: The study highlighted the correlation between neonatal E. coli bacteremia caused by phylogroup B2 and the role of colibactin. Results emphasize difference between male and female neonates in E. coli populations in bloodstream infections.