A method for counting acid-fast bacteria.

A reliable, convenient, and accurate method for counting ac id-fast hacteria ( AFB) is essential for much work with Mycobacterium leprae. The procedure used , previously in the laboratory (~, 4 ) had two technical difficulties: (a) In order for the drops to spread satisfactorily the microscope slides had to have a uniform wetability of the correct degree; sometimes this requirement was difficult to sa tisfy and a satisfactory procedure for one batch of slides was sometimes unsatisfactory for the next batch. (b) There was a tendency for bacteria in suspensions devoid of tissue to concentrate in the periphery of the drop during drying. Consequently a new method was developed, and, after the tes ts described below, it was substituted for the previous method.