An Uncommon Bug Causing a (sort of) Common Problem

On Monday Dr Li shared an exciting case of infectious endocarditis secondary to aerococcus urinae complicated by severe aortic valve insufficiency, eventually requiring valve replacement. What is aerococcus urinae, you ask? Great question.

Aerococcus Urinae:

  • Rare, gram +, alpha hemolytic, catalase negative cocci found in clusters or pairs
  • The Aerococcus genus was discovered in 1953 (the same year as the double helix!)
  • Historically underrecognized due to inability to culture
  • Risk factors: elderly (age 75), male and female affects, underlying urologic issues (e.g. BPH, prostate CA), catheterization
  • Presents as typical UTI, however UA negative for nitrites while positive esterase and protein
  • Management Pearl: typically RESISTANT to TMP-SMX, ciprofloxacin, but SUSCEPTIBLE to penicillins, cephalosporins. Notably some reports of VARIABLE SUSCEPTIBILITY to vancomycin

o Some sources cite the “drug of choice” to be pencillins

  • It is not uncommonly associated with the complications of bacteremia and endocarditis

With increasing ability to identify this organism we may begin to see it more in our clinical experiences and it will be prudent to keep our radars up, especially considering both its potential for complication and also resistance to some of our common empiric antibiotic choices.

In the event that aerococcus misbehaves, as was the case for Dr Li’s patient, let’s explore the indications for when to replace a left sided native valve endocarditis. Our experts at the AHA and IDSA list the following indications (level of evidence in parenthesis):

  • Signs or symptoms of heart failure due to valve dysfunction (1B)
  • IE complicated by annular abscess, heart block, or destructive perforating lesions (1B)
  • IE due to fungal infection or highly resistant organisms (1B)
  • Persistent infection (bacteremia or fever; >5-7 days) after appropriate antibiotic initiation, if other sources of fever or infection have been ruled out (1B)
  • Recurrent emboli or persistent/growing vegetations despite appropriate antimicrobial therapy (2a,B)
  • Severe regurgitation and mobile vegetation >10mm (2a,B)
  • Mobile vegetation >10mm (2b,C)

If you're visual like I am, please find below this ridiculous picture that captures these indications. Consider it a work in progress... I've been trying to spend more time on my creative expression.

Valve Replacement.jpg

Citations:

Christensen and Nielsen. Aerococcus urinae. Antimicrobe http://www.antimicrobe.org/b75.asp

Higgins and Garg. Aerococcus urinae: An Emerging Cause of Urinary Tract Infection in Older Adults with Multimorbidity and Urologic Cancer. Urol Case Rep. 2017 Jul; 13: 24–25. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5393163/

Zhang et al Aerococcus urinae in Urinary Tract Infections. J. Clin. Microbiol. April 2000 vol. 38 no. 4 1703-1705 http://jcm.asm.org/content/38/4/1703.full

Baddour et al. Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Compliations. AHA Scientific Statement Endorsed by Infectious Disease Society of America. Circulation. Oct 13 2015 http://circ.ahajournals.org/content/circulationaha/early/2015/09/15/CIR.0000000000000296.full.pdf