Abstract: The aim of this study was to investigate the antimicrobial resistance and virulence genes of Escherichia coli isolated from diarrhea sheep in Shaanxi Province. In this study, 54 diarrhea swabs were collected from 10 sheep farms. After purification, biochemical identification and 16S rRNA analysis, a total of 50 E. coli strains were isolated. For E. coli isolates, antibiotic resistance, resistance genes, and virulence genes were tested. The results showed that 49 E. coli strains display multiple-drug resistance, more than 90% of the strains were resistant to ampicillin, florfenicol, and sulfisoxazole, and 100% (50/50) of the strains were sensitive to meropenem. In addition, 8-11 resistant accounts for 68% of the total isolated strains (34/50). All strains carry 1-6 different resistance genes. Among them, Sul1 (64%), TetA (34%), bla_CTX-M (32%) had higher carrying rates, and bla_SHV (0%) was not detected. It is noteworthy that five ESBLs-strains carry the mcr-1 gene from the isolated. The results showed that the mortality rate of mice infected with the 50 strains of E. coli was 33%-100%, virulence genes were detected in 49 of the 50 isolates, with etrA showing the highest detection rate, accounting for 80% (40/50). The results indicated that the high proportion of virulence genes and the multidrug-resistance phenomena was prevalent in sheep pathogenic E. coli. The resistance phenotypes of β-lactams were basically not correlated with the resistance genes, suggesting that there might be multiple resistance mechanisms in the E. coli strains. The virulence spectrum of isolates was complex. This study provided a scientific basis for prevention and control of the pathogenic E. coli from sheep in Shaanxi area.

Key words: E. coli, pathogenic, antibiotic resistance, resistance genes, virulence genes