Correlation Between Microscopic Examination and Culture for Detection and Differentiation of Mycobacterial Isolates from Cattle in the Sudan

Abstract

One hundred and sixty seven caseated lymph nodes and tuberculous lungs were collected from cattle slaughtered in various locations in Khartoum State (Sudan) and examined bacteriologically. Microscopic examination using Zeilh-Neelsen stain and culture on Lowenstein-Jensen (L-J) medium were carried out to detect and differentiate between the mycobacterial species in the specimens. Thirty-five, 35 (20.96%) samples were found to harbor acid-fast bacteria when examined microscopically. Out of the 35 acid-fast bacteria, 22 (62.86%) showed branching filaments and were identified as Mycobacterium farcinogenes. The remaining 13 (37.14%) were bacilli and identified as Mycobacterium bovis. The 35 specimens that proved to harbor acid fast bacteria were cultured on L-J medium. None of the 22 specimens with branching filaments (Mycobacterium farcinogenes) grew on L-J medium when in. cubated aerobically at 37°C between four and eight weeks. 12 (92.31%) of the 13 bacilli (Mycobacterium bovis) showed visible growth using the above growth conditions. In conclusion, microscopic examination can only detect acid fast organisms in the clinical samples whereas culture on L-J medium can differentiate between acid-fast mycobacterial species.