Common Virulence Genes of UPEC
The most common virulence genes in uropathogenic E. coli (UPEC) include fimH (type 1 fimbriae), iron acquisition genes (fyuA, iutA, aerobactin), adhesin genes (pap, sfa/foc), and protectin genes (kpsMT, traT), with fimH being the most prevalent at 68-90% of isolates.
Major Categories of UPEC Virulence Genes
Adhesins (Most Critical for Pathogenesis)
fimH (type 1 fimbriae): The most prevalent virulence gene, detected in 58-90% of UPEC strains, encoding mannose-sensitive adhesins that mediate initial bladder colonization 1, 2
pap (pyelonephritis-associated pili): Present in 20-41% of isolates, encoding P fimbriae that facilitate kidney infection and ascending UTI 3, 2
sfa/foc (S and F1C fimbriae): Found in 21-34% of strains, contributing to tissue tropism and bacterial persistence 3, 2
afa (afimbrial adhesins): Detected in 8-20% of isolates, providing alternative adhesion mechanisms 3, 2
Iron Acquisition Systems (Essential for Bacterial Survival)
fyuA (yersiniabactin receptor): Highly prevalent at 70% of UPEC strains, facilitating iron scavenging in iron-limited urinary tract environment 4
iutA (aerobactin receptor): Present in 62% of isolates, working synergistically with aerobactin for iron uptake 4
aer/aerobactin: Found in 48-56% of strains, encoding siderophore systems critical for bacterial growth in urine 1, 4, 2
Protectins (Immune Evasion)
kpsMT (capsule synthesis): Detected in 58-61% of UPEC, encoding polysaccharide capsules that protect against phagocytosis and complement-mediated killing 1, 4
traT (serum resistance): Present in 66% of isolates, conferring resistance to serum bactericidal activity 4
Toxins (Tissue Damage)
hly (hemolysin): Found in 19-27% of strains, causing host cell lysis and tissue damage 3, 2
cnf (cytotoxic necrotizing factor): Detected in only 3% of isolates, inducing cytoskeletal rearrangements 2
astA/set (heat-stable enterotoxin): Present in 31% of strains, contributing to inflammatory responses 1
Additional Virulence Factors
usp (uropathogenic-specific protein): Highly expressed in 68% of UPEC during infection, though its exact function remains under investigation 1
iha (iron-regulated gene homologue adhesin): Expressed in 65% of strains, providing additional adherence capabilities 1
Clinical Implications
The most common virulence pattern involves co-expression of multiple genes (irp2/fim/iha/kpsMT/usp), exhibited by 14.4% of strains, indicating that UPEC pathogenesis requires coordinated action of adhesins, iron acquisition systems, and immune evasion factors 1. These virulence genes are predominantly found in phylogenetic groups B2 (34%) and D (28%), which represent the most pathogenic UPEC lineages 4.
The hemagglutination phenotype (primarily mannose-resistant) was present in 67-75% of isolates, reflecting the functional expression of adhesin genes and their crucial role in establishing infection 3. Importantly, 94% of UPEC strains are multidrug resistant, with virulence genes highly prevalent among antibiotic-resistant isolates, complicating treatment strategies 4.