CDC Study Looked at Mycobacterium Chimaera Outbreak at Wellspan York Hospital

A new study from the CDC found a link between an outbreak of  Mycobacterium chimaera and 3 heater-cooler devices used for cardiac surgery at Wellspan York Hospital in York, Pennsylvania. Laboratory testing suggested transmission occurred by aerosolization of Mycobacterium chimaera from 3T heater-cooler devices. The specific pathogen was Mycobacterium chimaera, a subspecies of Mycobacterium avium, a nontuberculous mycobacteria (NTM).

The findings of the new study are in this month’s Emerging Infectious Diseases, a publication of the Centers for Disease Control and Prevention (CDC).

The FDA and CDC (in this new study and elsewhere) have indicated that the design of certain heater-cooler devices appears to allow Mycobacteria to move from the device to the air to a patient’s open chest.

For additional information, please see the following:

Outbreak Investigation

The Pennsylvania Department of Health (PADOH) and the Centers for Disease Control and Prevention (CDC) did the following during a field investigation of the M. chimaera outbreak at Wellspan York Hospital in York, Pennsylvania:

  1. Conducted interviews with healthcare personnel at the hospital;
  2. Observed operating room practices during cardiac (heart) surgery;
  3. Reviewed the heater-cooler device manufacturers instructions for use;
  4. Collected water samples from the three HCDs used during the time outbreak patients had surgery, all three of which were no longer in use;
  5. Collected water from a scrub sink and 2 ice machines;
  6. Collected swab samples from the internal water reservoirs of the three HCDs;
  7. Operated an HCD in an empty cardiothoracic operating room and then collected water and air samples, including samples 18 inches from the HCD exhaust vent;
  8. Tested isolates of M. chimaera from 3 of the outbreak patients, the only isolates still available for testing, which included culture isolation, acid-fast bacillus staining, identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and 16S and rpoB sequencing, as well as molecular typing by pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing;
  9. Reviewed hospital infection-control practices and did not identify any breaches related to operating room ventilation, water use, storage, operating practices, or patient care.

In addition to the above, investigators dissembled one of the three HCDs and found biofilm on tubing and surfaces that would have been submerged in an internal water reservoir.

Mycobacterium chimaera was found in water samples from all three of the HCDs and in the swab of the biofilm found on the dissembled HCD. In addition, “air samples collected 18 inches from the HCD exhaust vent during the operating room simulations were found to be positive for M. chimaera after 2, 3, and 4 hours of HCD operation” (Lyman), which suggests airborne transmission occurred through aerosolization when the device was operating during surgery.

All 3 available case-patient M. chimaera isolates genetically matched isolates found in the HCDs and the air samples. According to the CDC they were found “highly related” by pulsed-field gel electrophoresis (PFGE), which was confirmed by whole-genome sequencing (WGS).

What are the Symptoms of Mycobacterium Chimaera?

The most common symptoms prior to severe illness are persistent fever, shortness of breath and unexplained weight loss.  However, most patients end up in the hospital with severe complications.

Untreated, this infection can be fatal.

It can take up to 6 years after surgery for symptoms to appear.

Source: Lyman, M. M., Grigg, C., Kinsey, C., Keckler, M., Moulton-Meissner, H., Cooper, E….Perkins, K. M. (2017). Invasive Nontuberculous Mycobacterial Infections among Cardiothoracic Surgical Patients Exposed to Heater–Cooler Devices. Emerging Infectious Diseases, 23(5), 796-805.