2. Methods and Measurements Reducing SSI risk from water heater/coolers units in cardiothoracic surgery Moya Alexander, Anan Ghazy, Kathleen Bamford, Eimear Brannigan, Hugo Donaldson, Henry Bishop, Jonathan Otter Imperial College Healthcare NHS Trust, London  jon.otter@imperial.nhs.uk @jonotter 1. Improvement issue and context A small number of patients undergoing cardiac surgery where cardiopulmonary bypass machines were used have developed a surgical site infection (SSI) with Mycobacterium sp.1 The Trust has experienced a case of SSI caused by Mycobacterium species following a cardiothoracic procedure. We report the measures implemented to reduce the risk of contaminated aerosols from heater cooler units (HCU) used in cardiothoracic surgery, guided by PHE, the MHRA, and the manufacturer.1-3 2. Methods and Measurements Water and air sampling commenced in June 2015. The frequency of disinfecting was increased in September 2015. The Trust has purchased a new HCU (increased from 5 to 6) to allow HCUs to be returned for manufacturer decontamination on a rotational basis, commencing September 2015. A dedicated tap with a point of use filter has been installed at Hammersmith for filling the machines. The HCUs have been located as far from the patient as possible, and surveillance for water-related organisms in SSIs has been enhanced. 3. Evidence of improvement All HCUs have grown Mycobacterium sp. in water and air. The proportion of air samples growing Mycobacterium sp. or overgrown with fungi was significantly lower after September 2015 (40% of 50 vs. 16% of 50, p=0.01). Use of disposable warming mattresses was maintained and decontamination of connectors included in disinfection routines. 4. Future steps We are looking at ways of capturing aerosols from the machines, and potentially moving HCUs out of theatres. Air and water testing for fungi has commenced to evaluate a potential further risk of aerosolising fungi in the theatre. The levels of Mycobacterium sp. are decreased and remain at a static level for both water and air. References Public Health England: Mycobacterial Infections Associated with Heater Cooler Units Used in Cardiothoracic Surgery. June 2015 v1. Sorin Group, Heater-Cooler System 3T, Operating Instructions. 2015 v 2. A Medical Device Alert from the MHRA on testing all types of heater/cooler devices for potential mycobacterium contamination. 11th June 15. Disclosures: JO is a consultant to Gama