Actinomyces gerencseriae hip prosthesis infection: a case report

INTRODUCTION Actinomyces bacteria are part of the human oropharyngeal microbiota. They have been associated with abdominal, cervicofacial and thoracic infections and a few cases of joint infections have also been described. In particular, Actinomyces gerencseriae, formerly described as Actinomyces israelii serovar II, has rarely been associated with human infections, mostly involving cervicofacial lesions and periodontal diseases. Here, we report one case of hip prosthesis infection due to A. gerencseriae. CASE PRESENTATION A 72-year-old Caucasian male developed an inflammatory collection on the outside of the right thigh where a hip prosthesis had been implanted for 11 years. Culturing a fluid sample from the collection puncture found Staphylococcus hominis and a Gram-positive bacillus unidentified by matrix-assisted laser desorption ionization time-of-flight mass-spectrometry (MALDI-TOF). Sequencing the 16S rRNA gene amplified from both the specimen and the isolate identified A. gerencseriae. Treatment adjusted with amoxicillin and trimethropim-sulfamethoxazole cured the infection. CONCLUSION The recently described A. gerencseriae has rarely been involved in human infections. We report the first case of A. gerencseriae joint infection in a hip prosthesis.