Genome-Wide Identification by Transposon Insertion Sequencing of Escherichia coli K1 Genes Essential for in vitro Growth, Gastrointestinal Colonizing Capacity and Survival in Serum

Escherichia coli K1 strains cause life-threatening infections in newborn infants. They are acquired from the mother at birth and colonize the small intestine, from where they invade the blood and central nervous system. It is difficult to obtain information from acutely ill patients that shed light on physiological and bacterial factors determining invasive disease. Key aspects of naturally occurring age-dependent human infection can be reproduced in neonatal rats. Here, we employ transposon-directed insertion site sequencing to identify genes essential for in vitro growth of E. coli K1 and genes that contribute to colonization of susceptible rats. The presence of bottlenecks to invasion of the blood and cerebrospinal compartments precluded insertion sequencing analysis but we identified genes for survival in serum.