Aerococcus urinae: An under-recognized cause of UTI

Received: 09-Jul-2018 Accepted Date: Jul 18, 2018; Published: 30-Jul-2018, DOI: 10.4172/2529-797X.1000034

Citation: Schempf TBS, Beg HMD, Tenner CMD. Aerococcus urinae: An under-recognized cause of UTI in internal medicine. Curr Res Integr Med 2018;3(S1):11-12.

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We present a case of an 84-year-old man with a history of advanced Alzheimer’s disease who was brought in after an episode of syncope in the setting of having a bowel movement. Evaluation was remarkable only for a positive urinalysis and a urine culture that ultimately grew >100,000 CFU/mL pan-sensitive Aerococcus urinae species. The patient was discharged on oral cefpodoxime with a diagnosis of vasovagal syncope and a urinary tract infection related to a relatively under-recognized organism.

Aerococci urinae is a Gram-positive, catalase-negative, bacterium that grows in clusters, often appearing in colonies that resemble Streptococci viridans [1]. Its genus was first described in 1953, with the first reported case of A. urinae in a human described in 1992 [1,2]. Several other species in the Aerococcus genus have been identified, including the pathogenic A. sanguinicola and the less-pathogenic A. christensenii and A. urinaehominus [3-5]. While rarely recognized in the past, A. urinae has become more commonly isolated in bacterial cultures, as bacterial detection has improved [6]. It has noted to be often confused with several other bacterial genii, including Streptococci, Staphylococci, and Enterococci [7]. In fact, one study showed that in a series of 820 isolates thought to be Streptococci species, 1% was found to be Aerococcus species on further evaluation [8]. Preliminary studies by Rasmussen et al. showed that the true incidence of Aerococci infections could be seven times that than previously described [7]. Genomic sequencing and mass spectrometry are the most sensitive modalities for detection of A. urinae, although many lower-resource clinical settings may not have access to this technology [9].

The organism has been implicated most commonly as a cause of urinary tract infection but cases of endocarditis and sepsis have been reported [6,10,11]. The incidence of Aerococci species isolated from urinary cultures is generally believed to range from 0.2%-0.8%; of these patients, it is unclear the proportion of which present symptomatically, with reported figures ranging from 50%-100% [12-16]. Of urine cultures positive for Aerococcus species, A. urinae was shown to represent 55%-65% [14,16,17]. As with most UTIs, A. urinae is seen more commonly in elderly patients [12-16]. One study showed that 67.5% of infected patients had underlying systemic diseases, most commonly diabetes mellitus, malignancy, and dementia [18]. Notably, several other types of infection due to A. urinae, as well as other Aerococcus species, have been described, including peritonitis, osteomyelitis, dental, joint, and soft-tissue infections [6,19-26]. While these cases are less common than UTI and endocarditis due to A. urinae, providers need to be aware of this pathogenic organism.

A. urinae is a pathogen that is much more common than previously described. Fortunately, it is generally sensitive to a number of antibiotics including beta-lactams, cephaloporins and carbapenems [27]. Rasmussen suggests ampicillin as a drug option of choice for sepsis from a urinary source, noting that cephalosporins and carbapenems are unnecessarily broad spectrum [7]. Unfortunately, there has been little investigation of treatment options in clinical trials, but in vitro studies have offered insight into treatment options for patients with A. urinae infections. Our patient exhibited a typical presentation for A. urinae infection, and in an ever-growing elderly population, knowledge and recognition of this potential pathogen is of increasing importance.

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