Aerococci have often been misidentified as streptococci in microbiology laboratories, leading to an underestimation of these bacteria as causes of human
infections. An increased awareness of aerococci and the introduction of matrix-assisted
laser desorption ionization time-of-flight mass spectrometry, has led to an increased isolation of Aerococcus urinae and Aerococcus sanguinicola from human urine and blood. The two species are found in human urine and can cause
urinary tract infections (UTI). Aerococcus urinae can, in older males with underlying urinary tract conditions, cause invasive
infections such as urosepsis or
infective endocarditis. The prognosis of invasive aerococcal
infections appears to be relatively favourable despite the old age of patients and their many comorbidities. Though clinical breakpoints are still not in place, aerococci seem to be sensitive to
penicillins,
carbapenems and
vancomycin. There is synergy between
penicillin and
aminoglycosides against some A. urinae isolates and this combination is often used in aerococcal
infective endocarditis. The treatment of complicated aerococcal UTI is not obvious as many isolates are resistant to
fluoroquinolones. In addition, A. urinae is resistant to
sulphamethoxazole, and there are methodological problems in the determination of
trimethoprim sensitivity. In complicated UTI,
ampicillin is probably a safe treatment option, whereas
nitrofurantoin is probably effective in uncomplicated UTI. Treatment studies in aerococcal
infections are needed as is a better understanding of the natural niches for aerococci and the pathogenesis and
clinical course of aerococcal
infections.