Aerococcus : an increasingly acknowledged human pathogen

Abstract

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.

A rare case of aerococcus urinae infective endocarditis

“…16S ribosomal RNA gene sequencing is the gold standard for accurate identification of Aerococcus , but this technique is costly, time consuming, and impractical for most diagnostic clinical microbiology labs. With improvement in diagnostic methods, especially matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), Aerococcu s has been increasingly recognized as a human pathogen [7–9]. MALDI-TOF MS is rapid, accurate, and has demonstrated good sensitivity and specificity in identifying aerococci.…”

“…With the recent advances in identification and increased recognition of Aerococcus as a cause of IE the incidence statistics is likely to be adjusted upward in the coming years. Other less common clinical conditions associated with A. urinae include lymphadenitis, peritonitis in peritoneal dialysis patients, soft tissue infections in genital area, postpartum infections and joint infection [7]. Cases of septic embolization to kidney, brain and cervical spine have been described.…”

Aerococcus urinae, a cause of cystitis with malodorous urine in a child: clinical and microbiological challenges

“…The underestimation of the clinical impact of this pathogen was mainly due to the fact that these facultative anaerobic, catalase-negative, Gram-positive cocci have a colony morphology on culture similar to that of α-haemolytic streptococci, while on Gram stain they appear in clusters like staphylococci [6]. In addition, aerococci share some features of antibiotic susceptibility with enterococci in that they exhibit intrinsic resistance to SXT [7] and nalidixic acid.…”

Clinical and microbiological features of Actinotignum bacteremia: a retrospective observational study of 57 cases

“…There are many similarities between A. schaalii and Aerococcus urinae [27]. Both species probably colonize the urinary tract and they have been difficult to correctly identify in the past.…”