Year: 2022 | Month: June | Volume 12 | Issue 3

Association Between Virulence Genes and Serogroups of Escherichia coli Isolates from Calves

M. Srivani Y. Narasimha Reddy K.V. Subramanyam M. Lakshman


Escherichia coli associated calf diarrhoea is a major economic concern for the dairy producers in this geographic area. The aim of this study is to investigate various pathotypes, virulence genes and their association with serogroups of E. coli isolated from diarrhoeic and healthy calves. A total of 194 rectal swabs were collected from diarrhoeic (129) and healthy (65) calves of different age groups from various districts of Andhra Pradesh and Telangana States. The E. coli were isolated and confirmed by cultural, biochemical and molecular testes. The virulence genes of E. coli pathotypes were detected using PCR with specific primers. Serogrouping was carried out at National Salmonella and Escherichia Centre, Central Research Institute, Kasauli, Himachal Pradesh. Out of 129 and 65 faecal samples (194) collected 60 (46.51%) and 21 (32.31%) samples were found positive for E. coli in diarrhoeic and healthy calves, respectively. Among different age groups, high rate of E. coli was isolated from 1-7 day old calves. Among the virulence genes of STEC, eaeA & hlyA genes were most prevalent in diarrhoeic (20%) and healthy calves (14.28%) and only stx1 was detected in diarrhoeic (6.66%) and healthy (4.76%) calves. The cnf2 (5%) and EAST1(3.33%) genes were detected only in diarrhoeic calves. The serogroup O157 which is having zoonotic significance was detected in STEC isolates from diarrhoeic and healthy calves. This study concluded that E. coli isolates from diarrhoeic calves are potential source of virulence genes and both diarrhoeic and healthy calves are the reservoirs of O157 serogroup in this geographic area.


  • E. coli isolation rate was high in calves of below one week age.
  • eaeA & hlyA genes were most prevalent among the STEC isolates from diarrhoeic and healthy calves.
  • Calves are reservoirs of O157 serogroup in this geographic region.

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