Virulence factors in <em>Escherichia</em> <em>coli </em>isolated from calves with diarrhea in Vietnam

Virulence factors in <em>Escherichia</em> <em>coli </em>isolated from calves with diarrhea in Vietnam

This study was conducted to determine the prevalence and characteristics of pathogenic <em>Escherichia</em> (<em>E</em>.) <em>coli </em>strains from diarrheic calves in Vietnam. A total of 345 <em>E. coli</em> isolates obtained from 322 diarrheic calves were subjected to PCR and multiplex PCR for detection of the <em>f5</em>, <em>f41</em>, <em>f17</em>, <em>eae</em>, <em>sta</em>, <em>lt</em>, <em>stx1</em>, and <em>stx2</em> genes. Of the 345 isolates, 108 (31.3%) carried at least one fimbrial gene. Of these 108 isolates, 50 carried genes for Shiga toxin and one possessed genes for both enterotoxin and Shiga toxin. The <em>eae</em> gene was found in 34 isolates (9.8%), 23 of which also carried <em>stx</em> genes. The Shiga toxin genes were detected in 177 isolates (51.3%) and the number of strains that carried <em>stx1</em>, <em>stx2</em> and <em>stx1/stx2</em> were 46, 73 and 58, respectively. Among 177 Shiga toxin-producing <em>E. coli</em> isolates, 89 carried the <em>ehxA</em> gene and 87 possessed the<em> saa</em> gene. Further characterization of the <em>stx</em> subtypes showed that among 104 <em>stx1</em>-positive isolates, 58 were the <em>stx1c</em> variant and 46 were the <em>stx1</em> variant. Of the 131 <em>stx2</em>-positive strains, 48 were <em>stx2</em>, 48 were <em>stx2c</em>, 11 were <em>stx2d</em>, 17 were <em>stx2g</em>, and seven were <em>stx2c</em>/<em>stx2g</em> subtypes. The serogroups most prevalent among the 345 isolates were O15, O20, O103 and O157.