Bacteriology
Clinical significance and antimicrobial susceptibilities of Aerococcus sanguinicola and Aerococcus urinae

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Abstract

A retrospective chart review was performed on 92 patients from whom 118 isolates of Aerococcus sanguinicola (n = 52) or Aerococcus urinae (n = 66) were obtained from urine cultures between October 2007 and June 2008 to assess clinical presentation and antimicrobial susceptibilities. The mean patient age was 82 (range 24–101) years. The majority was female (76% and 87% for A. sanguinicola and A. urinae, respectively) and institutionalized (61% and 60%, respectively). The majority of male patients had underlying prostatic disease (55% and 63%, respectively). Thirty-one of 46 patients with A. sanguinicola and 45 of 57 patients with A. urinae isolated from the urine had a clinical diagnosis of urinary tract infection. One subject had A. sanguinicola isolated from blood cultures. A. sanguinicola and A. urinae had low ceftriaxone, penicillin, and vancomycin MICs. MICs to erythromycin and levofloxacin were ≥0.5 and >4 μg/mL in 41% and 78% of A. sanguinicola and 17% and 23% of A. urinae isolates, respectively. In conclusion, A. sanguinicola and A. urinae are not infrequent causes of urinary tract infection and most A. sanguinicola isolates have elevated MICs to levofloxacin.

Introduction

Aerococci are Gram-positive organisms that have characteristics of both staphylococci and streptococci. They are catalase-negative, α-hemolytic, facultatively anaerobic, and form tetrads and clusters. The genus was initially described by Williams in 1953 as a single species, Aerococcus viridans (Williams et al., 1953). Since then, 6 additional members of the genus have been described: Aerococcus urinae (Aguirre and Collins, 1992), Aerococcus christensenii (Collins et al., 1999), Aerococcus sanguinicola (Lawson et al., 2001b), Aerococcus urinaehominis (Lawson et al., 2001a), Aerococcus suis (Vela et al., 2007), and Aerococcus urinaeequi (Felis et al., 2005).

A. viridans, A. urinae, A. christensenii, A. sanguinicola, and A. urinaehominis have been isolated from humans. A. sanguinicola is an apparently rare cause of urinary tract infection (UTI) and can cause bacteremia and endocarditis (Ibler et al., 2008). A. urinae has been isolated from urine and blood and is an apparently infrequent cause of UTI, bacteremia, endocarditis (Bruegger et al., 2009, de Jong et al., 2010, Ho et al., 2010, Kass et al., 2008), lymphadenitis (Santos et al., 2003), and spondylodiscitis (Astudillo et al., 2003). A. viridans is found in soil and is a rare cause of human infection with cases of bacteremia, endocarditis, and meningitis reported (Ruoff, 2007). A. christensenii has been isolated from the vagina (Collins et al., 1999), and A. urinaehominis from urine (Lawson et al., 2001a).

In this study, we elucidated demographics and antimicrobial susceptibilities of A. sanguinicola and A. urinae isolated from the urinary tract.

Section snippets

Materials and methods

A retrospective chart review was performed on 92 patients from whom A. sanguinicola (n = 52) or A. urinae (n = 66) were isolated from urine cultures between October 2007 and June 2008. Eleven patients had urine cultures positive for both organisms within this period. Two patients had 2 positive urine cultures, while 2 patients had 3 positive urine cultures for A. sanguinicola. Five patients had 2 positive urine cultures, while 2 patients had 3 positive urine cultures for A. urinae. The

Results

The Clinical Microbiology Laboratory at Mayo Clinic received 34 691 specimens for urine culture during the study period. A. sanguinicola was isolated from 0.15% and A. urinae from 0.19%. Thirty-one of 46 (67%) patients with A. sanguinicola isolated from urine were diagnosed with a UTI. Forty-five of 57 (79%) patients with A. urinae isolated from urine had a clinical diagnosis of UTI (Table 1). The mean age of patients was 82 years (range 24–101 years). The majority was female (76% and 87% for

Discussion

We recovered 52 A. sanguinicola and 66 A. urinae isolates from urine between October 2007 and June 2008. The majority of patients was older than 80 years, female, had a history of institutionalization, and was clinically diagnosed as having a UTI. We noted one serious complication; an 85-year-old man with a history of institutionalization and prostate disease developed A. sanguinicola urosepsis with bacteremia. A. sanguinicola (Ibler et al., 2008) and A. urinae (de Jong et al., 2010) have been

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Presented in part at the American Society of Microbiology General Meeting in Philadelphia, PA, on May 19, 2009.

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