Retrospective review of the clinical approach to the treatment and management of Aerococcus species bloodstream infections

Background: With the development and implementation of advanced microbiologic identification technologies, Aerococcus species, previously misinterpreted as α-hemolytic streptococci, is becoming increasingly recognized as a common human pathogen. In 2015, our institution identified over 500 unique A. species isolates from inpatient and outpatient cultures. Given the challenges surrounding the treatment of A. species infections, including the lack of interpretive clinical breakpoints and significant variation in antibiotic susceptibilities, we evaluated the clinical approach and management of Aerococcus species isolated from the blood at our institution.

Methods:  This was a retrospective chart review of adult inpatients (≥ 18 years) in which Aerococcus species was isolated from blood in 2015. The primary objective was to characterize the clinical approach to the treatment and management of Aerococcus species bloodstream infections (BSI). The secondary objective was to describe the clinical outcomes in patients treated for an Aerococcus species BSI.

Results: A total of 9 unique patients were identified for review with an average age of 74.6 years, 4 male patients. A history of diabetes mellitus was documented in 4 patients. A.urinae was found in 3 patients, A.viridans in 5 and no further speciation in 1. The predominant suspected source was urinary (4 patients), followed by intraabdominal (1), skin/soft tissue (1), and respiratory (1). Antibiotic therapy included a penicillin based regimen in 3 patients, a cephalosporin in 2, a combination of antibiotic classes in 2, and vancomycin in 1. Contamination was suspected in 1 patient. The average antibiotic duration and hospital length of stay was 13 and 18 days, respectively. There was no documentation of BSI complications or metastatic disease. Readmission within 30 days was observed in 5 patients; 2 of which were thought to be secondary to an infectious cause; there were no deaths reported in 30 days.

Conclusion: Aerococcus species infections are becoming increasingly more recognized as a human pathogen at our institution. There is a wide variation to the clinical management of these infections which further emphasizes the need for provider education and approved susceptibility breakpoints for clinical use.