Childhood delayed septic arthritis of the knee caused by Serratia fonticola.

We report a first documented case of Serratia fonticola infection in a child with septic arthritis, after falling off his bicycle and an infection with hawthorn thorns. The aetiologic agent was found to be a S. fonticola strain which was first isolated from two synovial fluid samples, only after culture enrichment, with failure of DNA amplification. Accurate diagnostic was done, despite S. fonticola is often considered as an opportunistic pathogenic bacterium. Alone ciprofloxacin treatment was not sufficient to counteract the infection, which was eradicated only after surgical drainage performed twice successively, with secondary removal of a remaining thorn, and treatment with third generation cephalosporin combined with ciprofloxacin for another three months.