Rapid identification of Bacillus anthracis by microscopical observation of bacteriophage lysis

SUMMARY: When young growing filaments or microcolonies of Bacillus a n t h r d were treated with specific bacteriophage, fragmentation of the filaments followed by complete disintegration of the microcolony were visible microscopically within 2-3 hr. Other Bacillus species were unaffected by the phage. This technique is a simple one for accelerating the identification of Bacillus anthracis. Bacillus anthracis may be distinguished from the closely related B. cereus by its susceptibility to a specific bacteriophage (McCloy, 1951). The usual tech-nique for testing a suspected strain with phage consists in spotting the un-diluted phage on a bacterial lawn on agar, and observing for lysis after incuba-tion overnight (McCloy, 1951; Brown & Cherry, 1955). It seemed that identi-fication could be accelerated by applying the phage to the bacteria a t an earlier stage of their growth, and observing lysis microscopically. The experiments reported in this paper confirmed this prediction. METHODS AND RESU,L'I'S Bacteriophage. The bacteriophage used was a virulent mutant a ofsa tem