Virulence factors in Escherichia coli isolated from calves with diarrhea in Vietnam

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

Epidemiological Analysis of Shiga Toxin-producing E. coli Isolated in Gwangju, Korea, by Pulse-field Gel Electrophoresis

In Gwangju, Korea, over the last 4 years, human gastrointestinal infection caused by shiga toxin-producing E. coli (STEC) increased. The aim of this study was to ascertain the genetic relatedness of STEC strains by pulsed-field gel electrophoresis (PFGE), as no data on the molecular epidemiology of STEC in Gwangju has yet been published. The PFGE banding patterns were defined for 62 of the 67 STEC strains isolated from cattle and human. There were 11 clonal types in the 11 STEC strains of cattle origin. Among the 11 STEC strains from asymptomatic person, four O91 strains were 100% similarity in band profiles. In the STEC strains isolated from diarrhea patients, same serogroups were grouped to the same cluster; O111 stains were 89.5% similarity, O157 strains 80%, O26 strains 81.5%, and O103 strains 91% similarity, respectively. In conclusion, this is the first report that a large collection of STEC strains from Korea has been analyzed, and a high degree of diversity was observed among the strains analyzed by this technique. PFGE analysis revealed that the strains isolated from human and cattle were closely related within serotypes, and it was useful for epidemiological analysis of STEC. The importance and usefulness of active laboratory surveillance of STEC such as PFGE should be recommended.