Whole Genome Sequence Analysis of a B. cereus Strain Causing a Fatal Anthrax‐Like Pulmonary Infection

Abstract

A 39‐year‐old male presented with a rapidly progressive hemorrhagic anthrax‐like pneumonia. Within 3 days, the overwhelming systemic infection proved fatal. Microbial culture of antemortem and postmortem specimens grew pure cultures of Gram‐positive rods that were provisionally identified as Bacillus species. An autopsy was performed, and we characterized the genome of a strain isolated from the patient's blood within days using next‐generation sequencing technology. In addition, the genomes of sixteen strains recovered from different anatomic sites and time points were fully sequenced to assess intra‐host genetic variation. Whole genome analysis demonstrated that the fatal infection was caused by a previously unknown strain of B. cereus that was closely related to, but genetically distinct from, B anthracis. The exceptional virulence of this B. cereus strain was due in part to carriage of a pXO1‐like plasmid that encodes the tripartite anthrax toxin. The sequence data revealed the molecular determinants leading to the exceptional virulence of this organism, helped guide the institutional infection control response, and provided new insight to host‐pathogen interactions. This case exemplifies the value of autopsy and whole genome sequencing technologies to laboratory medicine.