Clinical Characteristics and Laboratory Identification of Aerococcus Infections: An Australian Tertiary Centre Perspective

Aerococci uncommonly cause urinary tract (UTI) and bloodstream infections (BSI). The clinical characteristics and laboratory identification rates of Aerococcus in the Australian context are unknown. A retrospective observational cohort study of patients with positive Aerococcus cultures between 2010 and 2015 was performed. Patients were analysed according to predefined "asymptomatic bacteriuria," "UTI," and "BSI" groups. Forty-seven [40 (85%) for urine and 7 (15%) for blood] isolates were identified [38% male, median age of 79 (IQR 62-85) years], with corresponding identification rates of 24.2/100,000/year for urine (0.02%) and 7.3/100,000/year for blood cultures (0.007%). Since the use of matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) identification rate in urine has increased from 14.7/100,000/year to 32/100,000/year (p=0.02). For urine isolates, 14 (35%) met the definition for UTI whilst 26 (65%) were "asymptomatic bacteriuria." Underlying urological abnormalities, catheterisation, and polymicrobial growth were common. Seventy percent of bacteriuria was treated regardless of colonisation or active infection status. Symptomatic patients were more likely to receive treatment (OR 7.2, 95% CI 1.4-35.3). In patients with BSI, 1 (14.2%) had endocarditis and 1 (14.2%) died. The majority of isolates were susceptible to penicillin (11/12 tested, 92%).