Application of multiplex PCR in detection of virulence genes in Escherichia coli isolates of bovine mastitis

Escherichia coli is a pathogen of worldwide importance, with reference to bovine mastitis and is the second most common etiological agent causing mastitis in cows (Bansal et al., 1990; Char et al., 1993) following Staphylococcus aureus. Conventionally, the differentiation between the avirulent E. coli associated with opportunistic infections and the virulent E. coli isolates that cause disease was difficult. A number of virulence factors were reported to be involved in survival of E. coli in host. The determinants of the virulence have been much less extensively studied in E. coli isolates from bovine mastitis cases. In the present study, multiplex PCR was employed for identification of virulence genes in 40 E.coli isolates by targeting the virulence genes such as iss (increased serum survival), fim-C (Type I fimbrie), iuc-D (Aerobactin production) and tsh (temperature sensitive haemagglutination). Out of 40, thirty six isolates contained at least one of the targeted virulence genes. Among the isolates, 30 (75%) were positive for fim-C gene, 20 (50%) for iss gene, 9 (22.5%) for tsh gene and interestingly in none of the isolates, the presence of iuc-D was detected. Application of this method was found useful in identifying the highly pathogenic E. coli isolates from bovine mastitis.