Need for Pathogen Specific Diagnosis Expected to Increase as Antibiotic Use Decreases

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Farmscape for July 26, 2022

Full Interview 13:40 Listen

A Professor with Western College of Veterinary Medicine predicts, as the use of antibiotics decreases over the coming years, there will be a greater need to diagnose specific pathogens. The Brachyspira Diagnostic Service, operated by the Western College of Veterinary Medicine in collaboration with Prairie Diagnostic Services, provides full-service testing for Brachyspira, a genus of bacteria, several species of which cause diarrhea in pigs. Dr. John Harding, a Professor with Western College of Veterinary Medicine, says testing involves either PCR or culture, the selection of which depends on the diagnostic question.

Clip-Dr. John Harding-Western College of Veterinary Medicine:
In the simplest form the diagnostic question could be, is a particular species of Brachyspira present in the sample?
If that’s the case we would run typically a species-specific PCR and that could be hyodysenteriae or hampsonii but sometimes the question is broader in nature. That could be, what Brachyspiras are present in the sample or it could be are any Brachyspiras present in this sample in the case of testing in a negative farm? In those situations, a broader selection of tests which would include specific media or some of the species-specific PCRs or we even have a genus-specific PCR would be followed by sequencing. The other diagnostic question that sometimes is asked is, what antibiotics would be most effective? That’s a difficult ask to determine antibiotic sensitivity with Brachyspira because the organism doesn’t grow particularly well on culture. Our approach to that has been to develop several PCR tests that typically imply some information pertaining to resistance of specific antibiotics that we use commonly on the farm.

Dr. Harding acknowledges the call for antibiotic sensitivity testing has been limited, probably due to the fact that the most commonly used antibiotics on farm are still fairly effective in western Canada compared to other parts of the world where a lot more resistance has developed.

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