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SCVP Unknown Case 20

  This is a bioprosthetic valve removed from the aortic valve position, originally placed 10 years earlier. The patient presented with fevers, night sweats, and cutaneous lesions.

 

 

 

 

 

 

 

 

 

 

 

Mycobacterium chimaera


  • Below is an image of a Ziehl-Neelsen stain for acid-fast bacilli, with numerous small acid-fast organisms consistent with Mycobacterium species.  Mycobacterial infection of prosthetic valves are rare and can present years after the original surgical procedure. The vast majority are nontuberculous mycobacteria (NTM), such as M. chelonae, M. fortuitum, and M. abscessus. The diagnosis of this rare entity can be challenging, however, due to frequently negative blood cultures and sometimes minimal features of “classic” infectious vegetations, as would have been more likely for a Group A streptococcus infection.
  • In this case, the organism was typed as Mycobacterium chimaera. M. chimaera infection has been associated with open heart surgery beginning in January 2012 through approximately the end of 2014. The infection was linked to heater-cooler devices used during surgery, and which were thought to be contaminated and aerosolizing the agent into the surgical field. Symptoms of infected individuals are insidious and non-specific, meaning that the microorganism can have time to disseminate and establish itself prior to detection. Most commonly, the histology is associated with granulomatous inflammation (as might be expected in a mycobacterial infection), with positive stains for acid-fast bacilli. Overall, the risk of infection in patients undergoing open heart surgery during this time period is extremely low, but nevertheless this entity should remain on the differential diagnosis in the right clinical circumstances. 
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  • The CDC website contains additional information.
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    - Melanie Bois

     

     

     

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