Bacillus mycoides bacteremia after dog bite trauma in a patient on chronic suppressive antibiotics

<i>Bacillus mycoides (B. mycoides)</i> is a Gram-positive bacillus belonging to the Bacillaceae family, found in soil and plant rhizospheres. Infection of humans by <i>B. mycoides</i> is exceedingly rare, previously reported only twice in the literature. Here, we present a third case of <i>B. mycoides</i> infection, specifically a bloodstream infection in a patient following a dog bite to the hand. The patient, who had a chronic Left Ventricular Assist Device (LVAD) in place and was on a chronic suppressive regimen of doxycycline and cefadroxil for a preexisting driveline infection, developed <i>B. mycoides</i> bacteremia despite ongoing antibiotic therapy. She was successfully treated with intravenous ampicillin-sulbactam plus vancomycin, followed by oral ciprofloxacin upon discharge. The patient's recovery was uncomplicated and the final susceptibility testing confirmed pan-susceptibility to all tested agents. This case highlights the potential pathogenicity of <i>B. mycoides</i> in humans and raises questions on the risk factors for infection and optimal management of <i>B. mycoides</i> infections in the setting of relatively limited clinical data.