Heater-cooler devices used in cardiac surgery continue to be implicated in patient infections, and the take-home lesson from one recently reported outbreak is use only sterile water in the units.
Use of municipal tap water emerged as a risk factor in an investigation of Mycobacterium abscessus outbreak in nine cardiac surgery patients, said Arthur W Baker, MD, MPH, of the Duke Center for Antimicrobial Stewardship and Infection Prevention in Durham, NC. Four (44%) patients died of M. abscessus infections, Baker said recently in San Diego at the IDWeek conference.
The outbreak was somewhat different in that the majority of infections linked to heater-coolers have been caused by Mycobacterium chimaera.
“M. abscessus has a tendency to form biofilms and for this reason can be persistent in the environment,” Baker said. “It can be found in municipal water supplies, and therefore it can be found in hospitals that use municipal water.”
Heater-cooler units used in cardiac surgery have exhaust fans that can aerosolize bacteria over the sterile operating field if biofilms form within the unit. After a case was identified, a retrospective review was conducted to find all patients who underwent cardiac surgery and had positive cultures for M. abscessus from 2013 to 2016. Of the nine patients who met the case definition, seven (78%) were infected after valve replacement.
“Median time from suspected inoculation in the operating room to first positive culture was 49 days (range 38-115 days),” Baker and colleagues reported.1 “Seven (78%) patients had bloodstream infections, and six (67%) patients had sternal wound infections. Six (67%) patients developed disseminated disease with infection at multiple sites.”
In addition to switching to sterile water, the hospital decided to purchase new heating-cooling units because the devices are notoriously difficult to completely disinfect once they have been implicated in an infection. The hospital now is using an enhanced disinfection protocol and has seen no more infections linked to the devices since the intervention.
Treatment cured five patients, but the infections were difficult to clear. In addition to antibiotics, the patients had to undergo multiple surgeries.
“Five patients required multiple sternal debridements,” Baker said.
Though other patient deaths were not directly caused by M. abscessus, only one patient still survived when Baker reported the case at IDWeek.
- Baker AW, Maziarz EK, Lewis SS, et al. Invasive Mycobacterium abscessus Infection after Cardiac Surgery: Epidemiology and Clinical Outcomes. Abstract 999. IDWeek 2017. Oct. 4-8, 2017. San Diego.