Surgical wound infection following open humeral fracture caused by Mycobacterium houstonense: a case report

Historically Mycobacterium houstonense belongs to the unnamed third biovariant complex of the Mycobacterium fortuitum group, which are sorbitol positive. To date, there have been few reports of human infection induced by M. houstonense worldwide. We describe the case of a 68-year-old man with surgical wound infection, following an open humeral fracture, caused by M. houstonense and Escherichia coli. An implant bone plate had been embedded for internal fixation during surgery on the humeral fracture previously. A week later E. coli was isolated from the skin wound secretions. Cefoperazone-sulbactam was used for treatment for two weeks but the infection was not controlled, with a subsequent risk of deep wound infection. External fixation of the fracture was then performed instead of internal fixation. Ten days later, M. houstonense was isolated from new wound secretions. M. houstonense was identified by the molecular sequencing method. The TREK Diagnostic System was used to test the susceptibility to antibiotics by the microbroth dilution method. Levofloxacin and amikacin were used for treatment according to the results of the susceptibility test and the patient's condition obviously improved. To the best of our knowledge, this is the first case in China of human surgical wound infection caused by M. houstonense following open humeral fracture. The combination of levofloxacin and amikacin was effective in the treatment of M. houstonense infection.