Decontamination of heater-cooler units associated with contamination by atypical mycobacteria

Background: Non-tuberculosis mycobacteria such as Mycobacterium chimaera are found widely in hospital water systems. Invasive M. chimaera infections have recently been attributed to heater-cooler units (HCUs) of cardiopulmonary bypass equipment.

Aim: To assess the extent of microbiological contamination within the HCUs and to inform decontamination strategies for reducing the microbial load.

Methods: Water samples taken from HCUs used at University Hospitals Birmingham for cardiopulmonary bypass surgery were sampled to determine the number of micro-organisms by membrane filtration. Various decontamination processes were used throughout the study, all based on the manufacturer's guidance.

Findings: Total viable counts >300cfu per 100mL containing a wide variety of micro-organisms were obtained from water inside the HCUs. Working with the manufacturers, we significantly reduced the microbial load of the water within the HCUs by removing the internal tubing soiled with biofilm followed by a weekly decontamination regimen with peracetic acid.

Conclusion: A decontamination cycle including an initial replacement of internal tubing with weekly microbiological water samples is required to maintain the water quality within HCUs at an acceptable level.