Coliform mastitis is still significantly problematic disease to treat and control in practice, which is testament to the intricacy and mutability of the condition. We examined 103 mastitis E. coli isolates collected from 22 dairy farms in eastern China, for their serotypes and prevalence of virulence and antimicrobial resistance genes. Of the sixteen serotypes characterized through serum agglutination test, O39 followed by O92 and O123 were the most predominant serovars. The genotyping of the isolates was also determined by using ERIC-PCR. Phylogenetic analysis of DNA fingerprints was performed by using SPSS data editor, which yielded ten distinct genotypes (A-J). 14 virulence genes and 10 antimicrobial resistance genes were checked in all 103 isolates by PCR assay. Most prevalent virulence genes were, TraT, FimH, papC, iucD, F4 (K88) and sfa; but F17A, F41, stx1, intimin, CNF1, CNF2, LT and ST were not present in any isolate. Among all investigated resistance genes, 48% isolates carried CTX-M and qnrS. In addition, tetA, tetB, sul1, sul2 were also found in high frequency. Statistical analysis revealed an unconditional association between virulence and resistance genes as the P<0.05. To our knowledge, this is most updated report on serotypes, genotypes, prevalence of resistance and virulence genes, and their significant association with each other in mastitis E. coli isolates from eastern China.

Key words: E. coli, Genotypes, Mastitis, Resistance genes, Serotypes, Virulence