45 - in Silico Identification of Virulence Factors That May Contribute to Enhanced Gut Colonization of ESBL e. Coli

Background: The rapid global spread of extended spectrum beta lactamase-producing Escherichia coli (ESBL-E) strains threatens our ability to the treat many common infections and have become a major threat to public health. Some ESBL-E have a fitness advantage allowing them a competitive edge in gut colonization contributing to their global spread. We aimed to conduct in silico molecular characterization of virulence factors that may contribute to this fitness advantage.

Methods: For this observational study, we report data from fifteen whole-genome sequenced ESBL-E isolates found in the stool of a cohort of otherwise healthy infants. These strains were compared to MG1655 (commensal E. coli) and UTI89 (pan-sensitive uropathogenic E. coli). Phenotypic growth curves were done in minimal media with glucose as the only carbohydrate source. The genome sequences were assembled and annotated using Pathosystems Resource Integration Center (PATRIC) database and used to predict antibiotic resistance genes (ARGs) as well as virulence factors that may be driving the competitive advantage of these strains.

Results: All ESBL E. coli strains encoded multiple ARGs including those that target beta-lactams, aminoglycosides, fluoroquinolones, tetracyclines and macrolides. Growth curves in minimal media showed enhanced growth of some ESBL E. coli compared to control strains (Figure 1). ESBL-E strains 7 and 8 were also shown to have a higher copy number of carbohydrate metabolism genes. Proteome comparison of ESBL-E to MG1655 or UTI89 identified 93 and 321 proteins, respectively, with < 50% homology to the corresponding protein in the comparator strains (Figure 2). However, only 29 proteins across all ESBL-E were showed non-homology to both MG1655 and UTI89. These included both fimbrial and phosphotransferase system proteins.Figure 1
Figure 2A
Figure 2B


Conclusion: ESBL-E strains may use a combination of attributes to out-compete commensal or non-resistant E. coli. These may include enhanced carbohydrate metabolism, increased adherence to the epithelial cells (via fimbrial proteins) or greater efficiency of carbohydrate uptake from the environment (via the phosphotransferase system). Further in vitro and in vivo studies are in progress to verify these in silico observations.