**14. Relationship between antibiotic resistance and virulence or phylogenetic background in UPEC**

Previous studies show that in *E. coli* isolates from patients with urosepsis, resistance to antimicrobial agents such as ampicillin, sulfonamides, tetracycline, chloramphenicol, and streptomycin is negatively associated with virulence and a phylogenetic group B2, but positively associated with host compromise (immune deficiency, diabetes, and other urinary anatomical abnormalities) [26]. There is a similar negative association between FQ resistance and VFs and group B2 [142–144]. This suggests that, resistance may provide a greater fitness advantage to *E. coli* than traditional VFs or a group B2 background, allowing them to cause infections in compromised hosts with weakened defenses who are frequently exposed to antibiotics.
