CCMS Medicine Winter 2017 - 9

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genome sequencing (WGS) tests strongly suggest a point-source
contamination of LivaNova 3-T HCDs with M. chimera."
Mycobacterium chimera is a recently identified member of the
M. avium (MAC) complex, very similar to M. intracellulare. These
are slow-growing, environmental organisms which are usually
described as causing respiratory infections and disseminated
infections in immunocompromised patients. So perhaps the
current situation should not be too surprising, and indeed might
well have been predictable if only someone had had the prescience
to give it the proper amount of thought early on. Several outbreaks
of surgical site infections with nontuberculous mycobacteria
following heart surgery had previously been documented, some
reports going back to the late '70s and '80s. Many of those
identified other non-tuberculosis mycobacteria (NTM) species,
such as M. fortuitum, M. chelonae, and M. wolinsky, as well as M.
chimera.
On 10/13/16, the Associated Press (AP) reported that "health
officials are warning that small outbreaks of infections spread
by contaminated operating room machinery during open heart
surgery could be more widespread than first thought." According
to the CDC notice sent to alert doctors and hospitals then,
"contamination has been tied to 28 cases in the U.S., including at
least four who died." The manufacturer of the devices identified
the contamination in its factory in Germany in 2014 and
reportedly cleaned it up. However, bacteria traced to the devices
were linked to "clusters of illness in Switzerland, Pennsylvania,
Iowa, and Michigan."

The AP reports that 21 PA cases were reported by three
hospitals: WellSpan York Hospital, Penn State Hershey Hospital,
and Penn Presbyterian in Philadelphia. Five cases were reported
by the University of Iowa and Mercy Medical Center, and 2 cases
were reported by Spectrum Health Medical Center in western
Michigan. Canadian health officials are also sending letters to
thousands of former patients who "may have been exposed to this
rare infection" (www.cbc.ca/beta/news/canada/nova-scotia) and the
CDC is advising hospitals here similarly to notify patients at risk
(https//emergency.cdc.gov/han/han00397.asp).
Officials think the suspect Stockert 3-T machines, made by
London-based LivaNova, are used in roughly half of the 250,000
cardiopulmonary bypass operations performed in the U.S. each
year. In hospitals where at least one such infection has been
identified, the CDC estimates the risk of a patient getting an
infection from the bacteria was between 1 per 100 and 1 per 1000,
but there seems to be a higher risk for patients who had valves or
other products implanted, health officials say.
According to the IC&HE journal (vide supra), "this is now
considered an ongoing international outbreak" in which NTM
organisms are spread from the HCDs to the external air of the
operative area by airborne transmission. Further, experiments
with both smoke dispersal patterns and particle counts have
demonstrated that airborne M. chimera can only be detected
if both the HCD water was contaminated and the HCD was
turned on. The combined experiments helped demonstrate the
importance of the OR setup and the HCD orientation in the
room (Emerging Infectious Diseases, June, 2016)

Figure 1: Schematic representation of heater-cooler circuits tested for transmission of Mycobacterium chimaera during cardiac surgery despite an ultraclean air ventilation system. Blue arrows indicate cold water flow, and
red arrows indicate hot water flow and patient blood flow.
As indicated above in Figure 1, the:
* Blue arrows identify the cardioplegia circuit and show cardioplegia solution entering
the "heart lung machine." Cardioplegia is
used to stop the heart during surgery.
* Rectangles with zigzag lines are heat
exchange coils. They separate heater-cooler
fluid flow from patient fluid or blood flow.
* Red arrows identify the patient blood
circuit and show hot water flow and patient
blood flow.
Additionally, the water in the heater-cooler
device is isolated from the patient, cardioplegia solution and blood circuits.
Source: FDA website

Continued on page 10
WINTER 2017 | CHESTER COUNTY MEDICINE 9


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