Post-Cardiac Surgery Infection Associated with Different Diseases

By LabMedica International staff writers
Posted on 20 Jun 2018

Mycobacterium chimaera infection following cardiac surgery, due to contaminated cardiopulmonary bypass heater-cooler units (HCUs), has been reported worldwide. However, the spectrum of clinical disease remains poorly understood.

M. chimaera is an emerging pathogen causing disastrous infections of heart valve prostheses, vascular grafts, and disseminated infections after open-heart surgery. Growing evidence supports airborne transmission resulting from aerosolization of M. chimaera from contaminated water tanks of HCUs that are used with extracorporeal circulation during surgery.

Image: Mycobacterium chimaera colonies growing on agar; the infections can cause serious injury, including pneumonia and death. Of particular concern is that patients infected with M. chimaera may not develop symptoms and signs of infection for months to years after initial exposure, making the infections difficult to detect and diagnose (Photo courtesy of the CDC).

Scientists working with those at the Birmingham Heartlands Hospital (Birmingham, UK) reviewed 30 UK cases identified retrospectively through outbreak investigations and prospectively through on-going surveillance; and they reported clinical and laboratory features as well as treatment and outcome. Case definition was M. chimaera detected in any clinical specimen, history of cardiothoracic surgery with cardiopulmonary bypass, and compatible clinical presentation.

The team identified 30 patients (28 with prosthetic material) exhibiting a spectrum of disease including prosthetic valve endocarditis (14/30), sternal wound infection (2/30), aortic graft infection (4/30), and disseminated (non-cardiac) disease (10/30). Patients presented a median of 14 months post-surgery (maximum five years) most commonly complaining of fever and weight loss. Investigations frequently revealed lymphopenia, thrombocytopenia, liver cholestasis and non-necrotizing granulomatous inflammation. Diagnostic sensitivity for a single mycobacterial blood culture was 68%, but increased if multiple samples were sent. Survival analysis identified younger age, mitral valve surgery, mechanical valve replacement, higher serum sodium concentration and lower C-reactive protein (CRP) as factors associated with better survival.

The authors concluded that M. chimaera infection following cardiac surgery is associated with a wide spectrum of disease. The diagnosis should be considered in all patients who develop an unexplained illness following cardiac surgery. The study was published on May 24, 2018, in the journal Clinical Microbiology and Infection.

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Birmingham Heartlands Hospital