Molecular Characterization of Virulence Genes in E. coli Isolates from Bovine Mastitis Cases
Dinkar Darade
Department of Veterinary Microbiology, Krantisinh Nana Patil, College of Veterinary Science Shirwal-412801, Maharashtra Animal and Fishery Sciences University, Nagpur, India.
Mrunalini Budhe *
Department of Veterinary Microbiology, Krantisinh Nana Patil, College of Veterinary Science Shirwal-412801, Maharashtra Animal and Fishery Sciences University, Nagpur, India.
Uma Tumlam
Department of Veterinary Microbiology, Krantisinh Nana Patil, College of Veterinary Science Shirwal-412801, Maharashtra Animal and Fishery Sciences University, Nagpur, India.
Dushyant Muglikar
Department of Veterinary Microbiology, Krantisinh Nana Patil, College of Veterinary Science Shirwal-412801, Maharashtra Animal and Fishery Sciences University, Nagpur, India.
Prashant Mhase
Department of Veterinary Microbiology, Krantisinh Nana Patil, College of Veterinary Science Shirwal-412801, Maharashtra Animal and Fishery Sciences University, Nagpur, India.
Chandrashekhar Mote
Department of Veterinary Pathology, Krantisinh Nana Patil, College of Veterinary Science Shirwal-412801, Maharashtra Animal and Fishery Sciences University, Nagpur, India.
Rahul Kolhe
Department of Public Health, Krantisinh Nana Patil, College of Veterinary Science Shirwal-412801, Maharashtra Animal and Fishery Sciences University, Nagpur, India.
Prajwalini Mehere
Department of Physiology, Krantisinh Nana Patil, College of Veterinary Science Shirwal-412801, Maharashtra Animal and Fishery Sciences University, Nagpur, India.
*Author to whom correspondence should be addressed.
Abstract
The pathogenicity of Escherichia coli associated with bovine mastitis is primarily governed by the presence of specific virulence genes. The present study investigated the distribution and combinations of virulence determinants in E. coli isolates recovered from mastitic milk samples. A total of 36 E. coli isolates, confirmed by 16S rRNA gene amplification, were analysed for the presence of six virulence-associated genes (Stx1, Stx2, TraT, eaeA, aer, and hly) using polymerase chain reaction (PCR). Among the tested genes, three virulence determinants (Stx2, TraT, and eaeA) were detected, whereas Stx1, aer, and hly were absent. The Stx2 gene was the most prevalent, being detected in 58.33% of isolates, followed by TraT (41.66%) and eaeA (19.44%). The absence of Stx1, together with the higher frequency of Stx2, indicated a predominance of Stx2 among the Shiga toxin genes examined. Analysis of virulence-gene combinations revealed that Stx2–TraT was the most frequent profile (22.22%), followed by Stx2–eaeA and TraT–eaeA. The findings indicated that E. coli isolates from bovine mastitis harboured multiple virulence determinants associated with adhesion, toxin production, and immune evasion. The predominance of Stx2 and its association with other virulence genes highlighted the potential pathogenic relevance of these isolates. This study provides insights into the virulence-gene profiles of mastitis-associated E. coli, which may contribute to understanding disease pathogenesis and informing targeted control strategies. Further phylogenetic analysis of the selected virulent isolate revealed genetic divergence among the E. coli sequences, with isolate SQ4647 forming a distinct lineage.
Keywords: Escherichia coli, bovine mastitis, virulence genes, polymerase chain reaction, Stx2, TraT, eaeA, molecular characterisation, phylogenetic analysis, dairy cattle