Characterization and identification of Mycobacterium smegmatis in bovine mastitis

Twenty morphologically similar strains of a Mycobacterium sp isolated from milk of cows with bovine mastitis in the US Department of Agriculture dairy herd were identified as M smegmatis. Mastitis isolates submitted from Vermont and Washington also were identified as M smegmatis. A scheme for presumptive identification of rapidly growing mycobacteria was developed, using culture media and bacteriologic techniques commonly used in mastitis diagnostic laboratories. Important tests used were acid-fast staining, rapidity of growth, pigmentation, nitrate reduction, arylsulfatase activity, mucic acid utilization, acid production from galactose, rhamnose, and inositol, and growth at 45 C and 52 C.