Johnes PCR
While we have passed the check test for Johnes culture
by the National Veterinary Services Laboratory (NVSL) for
the past three years with high marks, we still want to improve
the turnaround time for diagnosing
Johnes disease. A PCR test has been developed and
validated. It will be applied to the bacterial culture tubes
for fecal specimens at two to six weeks after incubation.
Please note that we do not recommend eliminating the culture
but, if you need a faster presumptive diagnosis, the PCR can
help identify the positive shedders more quickly. Based on
our experience, we can detect bacterial colonies at the 8
week culture tubes; however, we can detect positive results
for Johnes disease by PCR from the same tube at 2-3
weeks after incubation before any colonies become visible.
For low shedders, it generally takes 12-16 weeks for the bacterial
colonies to be visible in the culture tubes; a swab taken
from the same tube at 4-6 weeks after incubation would give
positive PCR results for Johnes. If you need a quicker
presumptive diagnosis, it would be beneficial to request PCR
in addition to the routine culture request. There will be
an additional charge of $15.00 for each PCR requested.
Information needed
We would like to take this opportunity to thank
our users for their efforts in completing submission forms
in detail and providing us with differentials whenever possible.
This enables us to use the most appropriate reagents/media
for bacterial isolation and identification. Please continue
to provide with as much history, treatment and other relevant
information as possible.
-by Ching Ching Wu, Head of Bacteriology
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