Virulence-Associated Genes and Genetic Diversity of Avian Pathogenic (APEC) and Fecal (AFEC) E. Coli Isolates From Chickens
Background Avian pathogenic E. coli (APEC) is the etiologic agent of serious colibacillosis and causes extensive economic losses. To examine the genetic background of APEC, we characterized the serotypes, virulence genes, phylogenetic classification and MLST of 392 APEC and 586 AFEC strains isolated from infected chickens. Results The results showed that the most predominant serotypes were O78 (13.47%), O2 (9.16%), O18 (5.39%), O20 (4.42%) and O25 (4.09%). The major serotypes O78 (13.47%) and
... (9.16%) were significantly higher in the APEC isolates than in the AFEC isolates. Among the 16 analyzed virulence-associated genes (VAGs), iroN (100%), ompT (100%), fimC (92.46%), iss (77.91%) and irp2 (71.98%) were the most frequently identified. Over half (54.85%) of the strains possessed > 8–13 VAGs, and 85.23% of the strains carried iroN-ompT-fimC-iss/irp2 VAG patterns. According to the phylogenetic analysis, phylogroups A (32.11%) and B2 (31.36%) proved to be the most prevalent phylogenetic groups in the AFEC and APEC isolates, respectively. The strains that belonged to phylogroup B2 were associated with more VAGs. Based on MLST, 46 STs belonging to 15 different clonal complexes were identified, and 4 were novel. ST88 (10.67%) was found to be the most dominant ST, and it possessed at least 9 VAGs and belonged to phylogroups B2 or D. Furthermore, the isolates belonging to B2-O78/O2-ST88 were the most likely APEC isolates to be associated with epidemics, and they carried more VAGs than the other strains. Conclusions Our findings have enriched our knowledge of the molecular characteristics of APEC isolates from chickens, which will be important for the prevention and control of avian colibacillosis.