Musculoskeletal infections caused by Aerococcus urinae: a case-based review

Aerococcus are Gram-positive bacteria that have been historically misidentified using standard techniques. We report a case of a 63-year-old man with septic oligoarthritis caused by Aerococcus urinae (isolated in two ankle synovial fluid cultures and in two blood cultures). Due to the lack of evidence found in a search performed to identify similar cases, a systematic review was conducted with the objective to identify and analyze all documented cases of musculoskeletal infections caused by Aerococcus urinae. A total of 8 cases were selected: 6 spondylodiscitis, 1 periarticular hip abscess, and 1 prosthetic hip infection. Similarly, as in other Aerococcus urinae invasive infections, these were presented predominantly in older males with history of urinary tract disease, being identified mostly by sequencing of the 16S rRNA or by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), with an increasing incidence in the last years and generally with good sensitivity to beta-lactams (aminoglycosides were associated in some cases due to its synergistic effect). Additionally, 4 cases of musculoskeletal infections caused by Aerococcus viridans and 4 cases of Aerococcus urinae with ammoniacal and pervasive malodorous urine were identified; the last was a symptom also present in our case. In this review, we identify a recent increase of musculoskeletal infections caused by Aerococcus urinae, which as well as in series of other invasive infections could be well correlated with an increasing use of more sensible diagnosis methods in clinical laboratories. Therefore, we suggest that these probably will be more frequently diagnosed in the future.