Prevalence of pathogenicity island ETT2 in Escherichia coli isolated from piglets with diarrhea in northeast of China

Our aim was to investigate the prevalence of the pathogenicity island ETT2 and to examine the relationship between the ETT2 locus and other virulence factors in Escherichia coli (E. coli) isolated from piglets with diarrhea. A total of 354 E. coli strains isolated from scouring piglets were tested using PCR for the presence of the ETT2 locus. The E. coli strains were also analyzed for enterotoxins, fimbriae, non-fimbrial adhesin, Shiga toxins, pathogenicity islands, α-haemolysin (hlyA), afa8 gene cluster and autotransporter protease (sepA) genes. The results showed that 215 (60.7%) of the isolates possessed the ETT2 island. In 215 ETT2-positive E. coli strains, the virulence genes found were EAST1 (27.0%), irp2 (18.6%), paa (15.4%), STb (7.9%), LT (6.5%), ler (4.7%), hlyA (3.7%), AIDA-I (3.7%), K88 (3.7%), eae (3.3%), STa (2.8%), afaD (1.4%), afaE (1.4%), K99 (0.9%) and sepA (0.47%), respectively, and the isolates could be assigned into 25 different virulence factor patterns. In 139 ETT2-negative E. coli strains, the virulence genes detected were EAST1 (38.9%), paa (14.4%), STb (11.5%), AIDA-I (10.1%), irp2 (7.9%), sepA (2.16%), LT (0.7%), STa (0.7%), eae (0.7%), ler (0.7%), hlyA (0.7%) and K88 (0.7%), respectively, and the isolates could be classified into 13 different virulence factor patterns. Moreover, the occurrence of LT gene of ETT2-positive E. coli strains was far more than that of ETT2-negative E. coli strains.