Prevalence and characterization of the Shiga toxin producing Escherichia coli isolated from bovine mastitis
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Date
2020
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Department of Veterinary Microbiology, OUAT, Bhubaneswar
Abstract
The Shiga toxin producing E. coli is a main food-borne human pathogen threatening
public health worldwide. The significance of the STEC associated diseases outbreak
continuously increasing over the year and the STEC O157 serogroup is considered as an
important animal origin pathogen. It is also recognized as an important etiology of the bovine
mastitis which negatively impacts the animal health and dairy industry. As the “one health”
approach became more important in recent years. It’s mainly focuses on the zoonotic
diseases, environmental contamination and spread of antimicrobial resistance due to the
interaction between human, animal and their environment. The current research work was
done to determine prevalence and to characterize E. coli and Shiga toxin producing E. coli
isolated from bovine mastitis milk. A total of 250 bovine mastitis milk samples i.e., 172 cattle
and 78 buffalo samples were tested. On routine microbial examination and biochemical
characterization of the bacteria isolated from bovine mastitis milk, 27.20% (n= 68) were
positive for E. coli, out of which 10.27% (n= 7) are positive for the STEC O157 using sorbitol
MacConkey agar. On virulence factors such as serum resistance, Congo red dye uptake and
haemolysin activity showed 60.29%, 30.88% and 10.29% for total E. coli isolates and
85.71%, 71.43% and 42.86% for STEC O157 isolates respectively. Serum resistance was the
most common virulence activity shown by the bovine mastitis associated E. coli and STEC
O157 isolates. The biofilm production was determined by Congo red agar method, 75 % and
71.43% isolates of total E. coli and STEC O157 showed positive results respectively. By
microtiter plate assay E. coli showed 77.94% and 52.94% results, whereas STEC O157
showed 71.43 % and 57.16% results at 20 ˚C and 37 ˚C respectively. Microtiter plate assay
method showed more sensitivity for screening of biofilm production compared to Congo red
agar method. The antibiotic susceptibility test showed Gentamicin as most effective and
Ampicillin as most resistant by planktonic and sessile E. coli. Whereas Gentamicin,
Enrofloxacin, Ceftriaxone and Doxycycline were the most effective and Ofloxacin was the
least effective antibiotic by planktonic and sessile STEC O157. The multidrug resistance was
also evident in the E. coli and STEC O157 isolated from bovine mastitis milk samples. The
multidrug resistance is much higher in sessile form of E. coli compared to their planktonic
forms.
Description
TH - 6097