Using a multiplex PCR to differentiate between M. bovis BCG-vaccinated and pathogenic M. bovis-infected goats

Abstract

the ability of the Multiplex PCR diagnostic test to differentiate animals vaccinated with BCG from those infected with pathogenic Mycobacterium bovis. Nasal mucus, blood and organ tissue samples obtained from goats at necropsy, that had been either challenged with pathogenic M. bovis (Group 1, n=10), vaccinated with M. bovis-BCG/challenged with pathogenic M. bovis (Group 2, n=10), or vaccinated with M. bovis-BCG only (Group 3, n=4). All samples were analyzed using both the Multiplex PCR, and bacteriological culture. Blood and nasal mucus cultures were negative at all times, but the challenge strain was isolated from organ samples obtained post-mortem from Groups 1 and 2 (19/20). Negative results were obtained from the Multiplex PCR of nasal mucus samples obtained prior to challenge. A 150 bp amplification product -characteristic of pathogenic M. bovis- was obtained from 4 group-1 animals on d 60, and from 6 Group-1 animals on d 90. With the DNA from the cultures of Groups 1 and 2, amplification of pathogenic M. bovis was observed. None of the amplification products corresponded to M. bovis-BCG, confirming that the vaccine strain does not spread by either blood or nasal mucus. The use of Multiplex PCR in biologic samples (i.e. nasal mucus]) allowed distinguishing BCG-vaccinated animals from infected animals.