Aerococcus urinae

Background:

Aerococci are:

• Gram-positive cocci (GPC) that are arranged in tetrads and clusters
• Not in chains
• Catalase NEGATIVE.
  • Other genera that are GPC and catalase-negative that formclusters or tetrads:
    • Alloiococcus
    • Dolosigranulum
    • Gemella
    • Helcococcus
    • Pediococcus
    • Tetragenococcus
• Before 1992: a single species, Aerococcus viridans [PYR+, LAP+]
• Since 1992: four more species have been described:
  • Aerococcus urinae [PYR-, LAP-]
  • Aerococcus sanguinicola
  • Aerococcus christensenii
  • Aerococcus urinaehominis
    • Last 3 differentiated on the basis of 16-S

Laboratory Identification:

The Aerococcus sp. are sensitive to vancomycin, do not form gas from glucose, and are generally PYR positive but are LAP negative. All strains grow in broth containing 6.5% NaCl but do not grow at 10^oC or 45^oC. Strains are non motile and are strongly α-haemolytic. The strains grow well on blood agar media and form colonies somewhat smaller than the enterococci but larger than the viridans streptococci after overnight incubation.

Clinical Features:

• Aerococci occur in air, dust, vegetation, hospital environments, and meat-curing brines.
• Predisposing and associated features with A. urinae infection include:
  • male sex
  • age >65 years
  • preexisting urinary tract pathologies (prostatic hyperplasia, urethral stricture, and prior urinary tract surgery).
• A. sanguinicola is found in human infections and is frequently identified in clinical samples from elderly female patients with urinary tract infections.
• A. sanguinicola is similar to A. urinae in clinical implication, as both were first described as causes of urinary tract infections and then later found to be associated with bacteremia, sepsis, and endocarditis.
• A. sanguinicola has been isolated from blood cultures of patients with sepsis and endocarditis. A. viridans, the first Aerococcus species described, has been isolated from patients with meningitis, endocarditis, and bacteremia in neutropaenia and from HIV patients.

Treatment:

• Most of the reported cases have been treated with a betalactam as well as an aminoglycoside.
• Susceptibilities¹ were performed. Studies suggest an fairly constant antibiogram with susceptibility to penicillin and resistance to sulphonamides and aminoglycosides.
• Treatment options for A. urinae include:
  • Penicillins for less severe cases
  • Other cases: penicillin or vancomycin with gentamicin.

AMH.