The phylogenetic group, antimicrobial susceptibility, and virulence genes of Escherichia coli from clinical bovine mastitis

摘要

ABSTRACTBovine mastitis is still a central problem on dairy farms despite control programs, andEscherichia coliis a crucial pathogen during the development of bovine mastitis. The virulence genes, antimicrobial susceptibility, and mortality of mice infected with differentE. coliisolates from bovine mastitis were determined in this study. According to the presence of the specific geneschuA,yjaA, andTspE4.C2, these isolates mainly belonged to 2 different groups: group A (47/79) and group B1 (22/79). TheompCgene was detected in all the isolates, followed byfimH(89.9%),ECs3703(88.6%), andompF(73.4%), whereas most of the virulence genes were not detected in these isolates. The results of the antimicrobial susceptibility tests indicated that the isolates were susceptible to the fluoroquinolones and aminoglycosides. An inverse relationship was shown between the expression level ofompFand antimicrobial resistance; additionally, the isolates that were nonsusceptible to at least 4 classes of antimicrobial agents showed a lower mortality to mice in comparison with the susceptible isolates. This study indicated that antibiotic resistance had emerged inE. colifrom bovine mastitis in this area, and appropriate measures should be taken to avoid potential threats to humans and other animals.