Bovine lactoferrin maintains antibacterial effect against neonatal Escherichia coli septicaemia isolates despite the presence of iron acquisition genes

<b>Introduction.</b> <i>Escherichia coli</i> is a dominant cause of neonatal sepsis for which no prevention measures currently exist. Lactoferrin (LF) is an iron-sequestering antibacterial protein that has been noticed to decrease neonatal late-onset sepsis.<b>Hypothesis/Gap Statement.</b> LF's effect on <i>in vitro</i> growth of neonatal <i>E. coli</i> clinical isolates causing septicaemia is unknown. The prevalence of iron acquisition virulence genes which contribute to pathogenicity outcomes in these strains has also not been described in detail.<b>Aim.</b> To evaluate bovine lactoferrin's (bLF) effects on the <i>in vitro</i> growth of neonatal septicaemia <i>E. coli</i> isolates, and to determine the presence of iron acquisition virulence genes in these isolates.<b>Methodology.</b> <i>E. coli</i> clinical strains isolated from blood of septic neonates, including the archetypal RS218 strain, all representing prevalent phylogroups and multi-locus sequence types among neonatal invasive strains were studied. Strains were grown in batch growth with 0, 0.1, 1.0 and 10 mg ml^-1 bLF. OD measurements over time were used to generate growth curves, and the area under these curves was statistically compared using ANOVA or Kruskal-Wallis tests. Whole-genome sequencing (WGS) data were used to identify iron acquisition genes.<b>Results.</b> For all strains, growth decrease with 10 mg ml^-1 bLF compared to zero was highly significant (<i>P</i><0.001), and with 1 mg ml^-1 for some strains (<i>P</i>≤0.02). WGS showed that all neonatal strains carried several iron acquisition virulence genes, including <i>chuA</i>, <i>fyuA</i>, <i>irp2</i> and <i>sitA</i>. Additional siderophore genes were found in some strains.<b>Conclusion.</b> bLF is effective in impairing growth of neonatal sepsis-causing <i>E. coli</i> regardless of the presence of multiple iron acquisition virulence genes.