ObjectivesTuberculosis (TB) is the leading infectious disease in the developing world. Delayed-type hypersensitivity skin test diagnoses TB using tuberculin purified protein derivative (PPD), but this test is incapable of distinguishing Mycobacterium tuberculosis (MTB) infection from bacillus Calmette–Guérin (BCG) vaccination or an infection caused by nontuberculous mycobacteria (NTM). This study was performed to evaluate the use of recombinant early secretory antigenic target 6 (rESAT-6), a secretory protein found only in MTB, Mycobacterium bovis, and few other mycobacterial species, as a skin marker for MTB in guinea pigs.MethodsWe prepared recombinant MTB ESAT-6 and evaluated its use as a specific antigen for MTB in guinea pigs.ResultsOur results show that the purified MTB rESAT-6 antigen is capable of inducing a positive reaction only in guinea pigs sensitized to MTB. No such reaction was observed in the animals sensitized to M. bovis, BCG vaccination, or NTM (Mycobacterium avium).ConclusionOur study results confirm that the ESAT-6 antigen is more specific to MTB infection than PPD and could be used in more specific skin tests for detection of MTB in large animals and in humans.
Paratuberculosis is an important disease of ruminants with a worldwide distribution. In developing countries where funding constraints challenge establishment of control schemes, large losses are incurred on cattle farmers due to paratuberculosis. In this study, faecal specimens from Holstein-Friesian cows with progressed and moderate clinical paratuberculosis (N = 223) from 13 dairy farms in Isfahan, Central Iran, were subjected to bacterial culture. Culture growth diagnostic for M. avium subsp. paratuberculosis was found in cattle from nine of the 13 farms and in 71 of the cattle studied. These results illustrate the emergence of PTb in this region, and they imply that PTb should be given a higher priority for veterinary measures.
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