Detection of tuberculous and non-tuberculous mycobacterial species in trans-tracheal washes of cattle and buffaloes with respiratory distress.

Bovine tuberculosis (bTB) is a zoonotic disease that affects domestic and wild animals, including livestock. The purpose of the study was to detect tuberculous and non-tuberculous mycobacterial species from buffaloes and cattle with respiratory signs and positive intradermal tuberculin test. Eighteen trans-tracheal washes (TTW) were obtained from buffaloes (n = 5) and cattle (n = 13) with respiratory distress. All the collected samples were subjected to microscopic examination, direct PCR screening, and bacteriological culture in Middlebrook7H10 media followed by PCR. One sample revealed the presence of acid-fast bacilli on microscopic examination. Six out of eighteen TTW samples tested positive for the hsp65 gene indicative of the Mycobacterium genus. Two samples were positive through direct PCR and were further identified as Mycobacterium orygis and Mycobacterium kansasii. However, out of the 18 TTW samples, two samples yielded Mycobacterium kansasii isolates on culturing, which were confirmed using species-specific PCR. Our study indicates PCR is a better screening test of the TTW samples for the detection of both tuberculous and non-tuberculous mycobacteria compared to microscopic examination and culturing. The presence of non-tuberculous mycobacteria may affect the results of tuberculinization in cattle and PCR screening of the tested animals will assist in validating the tuberculin test results.