A preferential isolation procedure for asporogenous Gram-positive bacteria.

A preferential isolation procedure was devised for asporogenous (Asp), Gram-positive (Gp), aerobic or facultative anaerobic bacteria which included the genera Arthrobacter, Corynebacterium, Brevibacterium, Microbacterium, Mycobacterium, and Micrococcus (Asp-Gp bacteria). An antibiotics-mixture agar which contained 5 to 10 micrograms per ml of colistin, 10 to 20 micrograms per ml of nalidixic acid and 30 micrograms per ml of cycloheximide was used in the isolation. Using this technique 47 Asp-Gp bacteria representing 26 subgroups of coryneform bacteria and Micrococcus were isolated from 3 soil samples. The method was far more efficient than the standard dilution-plate technique. This preferential method is available to isolate Asp-Gp bacteria from a sample containing about 500-fold more of other Gram-positive and negative bacteria.