Abstract
Mycobacterium chimaera is a non-tuberculous mycobacterium, member of the Mycobacterium avium complex (MAC), which has become a global public health concern due to infection following cardiac surgery performed with contaminated heater-cooler units. M. chimaera infection is characterized by a long latency, non-specific signs and symptoms and high mortality rates. Thus, the diagnosis is still challenging both for forensic pathologists and for clinicians. Clinical manifestations of M. chimaera infection include endocarditis, hepatitis, nephritis, encephalitis and chorioretinitis. A constant histopathologic finding is the presence of non-caseating granulomas, with multinucleated giant cells and histiocytes. Hereby, we present two cases of fatal disseminated M. chimaera infection following aortic valve surgery reporting clinical history and post-mortem findings. Further, we provide a brief overview of the literature with a special focus on histopathological characteristics of M. chimaera infection. The aim of this article is to provide a complete synopsis of histopathological characteristics useful for forensic pathologists.
Highlights
Mycobacterium chimaera is a non-tuberculous mycobacterium first identified in 2004 [1], which is part of the Mycobacterium Avium complex (MAC)
In 2013, Achermann et al described the first cases of prosthetic valve endocarditis and bloodstream infection due to M. chimaera [5], while an outbreak of M. chimaera infections has been reported in 2015 among European patients who underwent open-chest surgery performed using a specific brand of heater-cooler devices (HCD) [6,7,8]
The first case of M. chimaera infection in Italy was described in December 2016, in a woman with a history of cardiac surgery who developed disseminated infection and vertebral osteomyelitis [9]
Summary
Mycobacterium chimaera is a non-tuberculous mycobacterium first identified in 2004 [1], which is part of the Mycobacterium Avium complex (MAC) It is an opportunistic pathogen responsible for respiratory infection mainly in immunocompromised subjects and in patients with underlying respiratory diseases such as cystic fibrosis [2]. M. chimaera has become a global public health concern due to infection following cardiac surgery because of contaminated devices, called heater-cooler units (HCU), used to regulate blood temperature during extracorporeal circulation [3]. It seems that M. chimaera forms biofilms in heater-cooler unit water tanks of contaminated devices and spreads through airborne transmission [4]. The first case of M. chimaera infection in Italy was described in December 2016, in a woman with a history of cardiac surgery who developed disseminated infection and vertebral osteomyelitis [9]
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