Mycobacterium chimaera Infection Following Cardiopulmonary Bypass Surgery Clinical Practice Guidelines (2019).

The International Society for Cardiovascular Infectious Diseases (ISCVID) issued guidelines in November 2019 for the diagnosis, treatment, and prevention of disseminated Mycobacterium chimaera infection following cardiac surgery with cardiopulmonary bypass.^[1]

Multidisciplinary Hospital Patient Management

Patients who develop Mycobacterium chimaera infection following cardiopulmonary bypass surgery should be managed by a multidisciplinary "Endocarditis Team."

Diagnosis

Imaging techniques

Transesophageal echocardiography is recommended for detection of cardiac vegetations and aortic root collections and for evaluation of valvular function.

Positron-emission tomography (PET)/CT imaging should be considered in patients with suspected aortic graft infection or fever of unknown origin (FUO).

Microbiological diagnostic algorithm for suspected M chimaera infection

Conventional blood cultures off antibiotics are recommended in patients with prosthetic rings/valves, aortic grafts, and mechanical circulatory devices who develop undefined febrile illness for which antimicrobials are being considered.

If the above conventional blood culture results are negative and cardiovascular infection is still considered among the differential diagnoses based on when the patient was exposed to a Stockert 3T heater-cooler device (3T-HCD) during cardiopulmonary bypass, multiple mycobacterial blood cultures are recommended. Mycobacterium genus–specific polymerase chain reaction (PCR) from whole blood should also be considered.

Acid-fast bacilli (AFB) staining and culture of cardiac or other affected tissues are recommended. Species-specific PCR or Mycobacterium genus–specific PCR followed by next-generation sequencing (NGS) from plasma should also be considered.

In patients with cytopenias, bone marrow biopsy for histology, staining, and mycobacterial culture should be considered.

In patients with FUO in whom initial mycobacteria blood cultures are unrevealing, consider repeat mycobacterial blood cultures and Mycobacterium genus–specific PCR from whole blood or NGS from plasma.

Histopathological diagnosis of M chimaera infection

Evaluate resected cardiac valve or other infected tissue and embolic fragments for possible mycobacterial infection.

Mycobacterium genus–specific PCR should be considered if histopathology findings show noncaseating granulomas and foamy swollen macrophages with or without acid-fast bacilli.

Antimicrobial Therapy

One- or two-drug therapy (especially macrolide monotherapy) is strongly discouraged owing to subsequent rapid development of macrolide resistance due to a 23S rRNA gene mutation and of amikacin resistance due to a 16S rRNA gene mutation.

Suggested regimens for wild-type M chimaera infection include the following:

First-line therapy: Azithromycin, rifampin (rifabutin), ethambutol, amikacin
Second-line therapy: Clarithromycin, rifabutin (rifampin), ethambutol, amikacin

Suggested regimens for drug-resistant M chimaera infection include the following:

Resistant to clarithromycin: Rifabutin/rifampin, ethambutol, amikacin, clofazimine
Resistant to amikacin: Clarithromycin, rifabutin/rifampin, ethambutol, clofazimine

Amikacin is recommended and should be continued as long as tolerated via peripherally inserted central catheter (PICC) as outpatient parenteral antibiotic therapy (OPAT).

Adverse drug reactions of antimicrobial agents and therapeutic drug monitoring

Vestibular function and audiograms should be monitored monthly in patients receiving amikacin and every second month in patients receiving macrolides.

Patients receiving ethambutol, linezolid, and/or rifabutin should undergo periodic ophthalmologic examinations (visual acuity, red-green color discrimination, confrontation visual field testing, and dilated fundus examination).

Patients receiving macrolides, quinolones, clofazimine, linezolid, and bedaquiline should undergo monthly electrocardiography.

Patients receiving amikacin should undergo weekly therapeutic drug monitoring (TDM). Patients with renal insufficiency receiving ethambutol should undergo TDM at baseline and until therapeutic levels reach a steady state.

Consider monitoring macrolide blood levels, especially in patients receiving rifampin combined with clarithromycin.

Susceptibility to antimicrobial agents

Experienced reference laboratories should conduct antimicrobial susceptibility testing of M chimaera isolates.

M chimaera isolates that have not been tested for antimicrobial susceptibility at baseline should be saved for future testing.

Clarithromycin and amikacin minimum inhibitory concentration (MIC) testing is recommended.

Surgical Approach

Consider revision surgery to remove all cardiovascular prosthetic material. All extracardiac foci in addition to cardiovascular sites should be included for source control.

Patient Notification, Screening, and Investigation

Consider notifying patients and providers regarding risks and signs and symptoms of infection.

Additional case finding through investigation and testing of patients with a history of exposure to 3T-HCD should be restricted to symptomatic patients.

For more information, please go to Coronary Artery Bypass Grafting.

For more Clinical Practice Guidelines, please go to Guidelines.

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