A case of unusual Gram-negative bacilli septic arthritis in an immunocompetent patient.

The Gram-negative bacilli Acinetobacter baumannii, Burkholderia cepacia, Ochrobactrum anthropi, Pseudomonas mendocina, Ralstonia spp., Serratia marcescens and Stenotrophomonas maltophilia are ubiquitous environmental organisms of low virulence, and do not usually cause illness in immunocompetent hosts. We report a case of multiple concurrent opportunistic Gram-negative bacilli causing septic arthritis in a healthy patient following trauma to the knee. Repeated operations, including arthroscopy, arthrotomy and debridement, were required before tissue cultures became negative. The patient also required an extended duration of intravenous and oral antibiotic treatment before he was discharged. Gram-negative bacillary septic arthritis is an uncommon but significant condition that requires repeated debridement and washouts in order to achieve bacterial eradication. This case report highlights the importance of an awareness of the external environment at the time of injury, as it impacts the type of organisms causing the infection, and consequently, the choice of empiric antibiotics required for successful treatment.