Bacillus Species Infective Arthritis after Knee Arthroscopy

BACKGROUND: Bacillus species infection of the joints is a very rare occurrence, with sporadic reports in the medical literature. CASE REPORT: A 67-year-old woman with osteoarthritis developed infection in the knee joint after arthroscopy. Percutaneous needle aspiration of articular fluid performed post-operatively showed a positive culture for Bacillus species. The diagnosis of septic arthritis was, however, not confirmed as the results were considered contamination. Failure of treatment with beta-lactam antibiotics on two occasions and successful cure of infective arthritis by long-term administration of a fluoroquinolone confirmed iatrogenic clinical joint infection with Bacillus species. CONCLUSION: Any clinically suspected joint infection must be treated as septic arthritis until proved otherwise.