A fluorigenic substrate for the rapid differentiation of Mycobacterium fortuitum from Mycobacterium chelonei on the basis of heat stable esterase activity.

A fluorigenic substrate, 4-methylumbelliferyl butyrate, enables mycobacterial esterase activity to be easily and rapidly detected and quantitated. By use of this substrate, the esterase activity of Mycobacterium fortuitum was found to be significantly more heat resistant than that of M. chelonei. On this basis, a rapid, simple and inexpensive test for the differentiation of these two species has been developed.