Distribution and Co-Occurrence of Selected Virulence-Associated Genes in Escherichia coli Isolates from Urban and Exhibition Pigeons.

Escherichia coli is a highly diverse bacterial species that includes strains with significant pathogenic potential for both animals and humans. Urban pigeons (Columba livia domestica) are widely distributed and frequently interact with human environments. In contrast, exhibition pigeons are maintained under controlled conditions, providing an opportunity to compare bacterial populations across different ecological settings. Comparative data on virulence-associated gene patterns between free-living urban and exhibition pigeon populations remain limited, particularly when both populations are investigated within the same geographical setting. The present study aimed to investigate the distribution and co-occurrence patterns of selected virulence-associated genes in Escherichia coli isolates recovered from urban and exhibition pigeons. A total of 453 faecal samples (153 urban and 300 exhibition pigeons) were collected, from which 133 Escherichia coli isolates were recovered (65 from urban and 68 from exhibition pigeons), corresponding to an overall isolation rate of 29.4%. A representative subset of isolates was independently confirmed by species-specific PCR and Sanger sequencing before virulence gene profiling. Subsequently, all isolates were screened for six virulence-associated genes (fimC, ompA, tsh, hlyA, astA, and iroN) by PCR. Virulence gene prevalence, gene profiles, co-occurrence patterns, and virulence scores were analysed, and statistical comparisons between groups were performed. The most prevalent gene was ompA (88.0%), followed by fimC (66.2%) and iroN (32.3%), whereas hlyA was detected only sporadically (3.8%). The most common virulence profile was fimC + ompA (24.8%), followed by ompA alone (20.3%). Co-occurrence analysis identified fimC and ompA as the most frequently co-detected gene pair (79/133 isolates; 59.4%); however, their association was weak and not statistically significant (φ = 0.078, p = 0.371). Frequent co-detection with the iron acquisition-associated gene iroN was also observed. No statistically significant differences were observed in the distribution of the investigated virulence-associated genes between urban and exhibition pigeon isolates, although urban isolates exhibited a broader diversity of gene combinations. In conclusion, pigeon-derived E. coli isolates harboured diverse combinations of selected virulence-associated genes, with adhesion-associated genes being the most frequently detected determinants. These findings provide baseline data on the distribution of selected virulence-associated genes in pigeon-derived Escherichia coli isolates and support future studies incorporating additional virulence markers, whole-genome sequencing, and comparative analyses to understand their epidemiological relevance better.