The Type 6 Secretion System (T6SS) plays a role in the pathogenesis of strain NMEC15.

Neonatal meningitis Escherichia coli (NMEC) is the second leading cause of sepsis and meningitis in newborns with fatality rates of 15-40 %. Survivors may suffer lifelong neurological sequelae such as cerebral palsy, seizures, hearing loss, and delayed development. Despite identification of virulence factors contributing to meningitis, the pathogenesis of NMEC remains to be elucidated. The Type 6 secretion system (T6SS) has been identified in the type strain NMEC RS218 and its associated Hcp proteins were shown to play a role in invasion, cytoskeleton rearrangement, and apoptosis of human brain microvascular endothelial cells (HBMEC), which constitute the blood-brain barrier (BBB). The aim of this study was to assess T6SS prevalence in a collection of NMEC and characterize the T6SS in NMEC 15. Here, we analyzed the prevalence of selected T6SS genes hcp, impK, evpB, vasK, and icmF in a collection of NMEC and their potential role in the adhesion and invasion of HBMEC and the differentiated macrophage cell line THP-1, and resistance to Dictyostelium discoideum predation by NMEC15. We show that ImpK and IcmF are involved in NMEC 15's adherence to HBMEC, and Hcp, ImpK, and IcmF are involved in invasion. The amoeba D. discoideum was used to demonstrate functionality of the T6SS with greater numbers of amoeba required to kill the WT NMEC15 compared to the hcp deletion mutant. These studies provide further evidence of the potential role of T6SS in NMEC pathogenesis.