A Unique Isolation of a Lytic Bacteriophage Infected <i>Bacillus anthracis</i> Isolate from Pafuri, South Africa

<i>Bacillus anthracis</i> is a soil-borne, Gram-positive endospore-forming bacterium and the causative agent of anthrax. It is enzootic in Pafuri, Kruger National Park in South Africa. The bacterium is amplified in a wild ungulate host, which then becomes a source of infection to the next host upon its death. The exact mechanisms involving the onset (index case) and termination of an outbreak are poorly understood, in part due to a paucity of information about the soil-based component of the bacterium’s lifecycle. In this study, we present the unique isolation of a dsDNA bacteriophage from a wildebeest carcass site suspected of having succumbed to anthrax. The aggressively lytic bacteriophage hampered the initial isolation of <i>B. anthracis</i> from samples collected at the carcass site. Classic bacteriologic methods were used to test the isolated phage on <i>B. anthracis</i> under different conditions to simulate deteriorating carcass conditions. Whole genome sequencing was employed to determine the relationship between the bacterium isolated on site and the bacteriophage-dubbed <i>Bacillus</i> phage Crookii. The 154,012 bp phage belongs to <i>Myoviridae</i> and groups closely with another African anthrax carcass-associated <i>Bacillus</i> phage WPh. <i>Bacillus</i> phage Crookii was lytic against <i>B. cereus sensu lato</i> group members but demonstrated a greater affinity for encapsulated <i>B. anthracis</i> at lower concentrations (<1 × 10⁸ pfu) of bacteriophage. The unusual isolation of this bacteriophage demonstrates the phage’s role in decreasing the inoculum in the environment and impact on the life cycle of <i>B. anthracis</i> at a carcass site.