Introduction. Recent reports implied heater-cooler units (HCU), which are used for warming of infusions, blood or in ECMO devices, as possible origin of healthcare-associated infections (HAIs) with potentially pathogenic bacteria like nontuberculous mycobacteria [1]. This represents a source of contamination in a usually sterile setting. Aim of this study is to analyse water from infusion heating devices (IHDs) for bacterial contamination and to raise the question if IHDs act as a possible source in the transmission of HAIs. Methods. 300-500 ml of thermal transfer fluid (TTF) derived from the reservoirs of 22 independent IHDs were collected and processed on different selective and non-selective media for colony count and identification of bacteria. Strains of Mycobacterium species (spp.) were further analysed by whole genome sequencing. Results. Bacterial growth was observed in each of the 22 collected TTFs after cultivation at 22°C and 36°C. Pseudomonas aeruginosa was the most frequent pathogen identified, being present in 13.64% (3/22) at >100 CFU/100mL. Colonization with Mycobacterium chimaera, Ralstonia pickettii and Ralstonia mannitolilytica was detectable in 9.09% (2/22) of the isolates. Primary sequencing of the detected M. chimaera suggests a close relationship to a M. chimaera strain detected in an outbreak in Switzerland, which led to the death of two patients. Discussion. A contamination of the TTF represents a germ reservoir in a sensitive setting. Handling errors of the IHD may lead to distribution of opportunistic or facultative bacterial pathogens, increasing the risk of nosocomial infection transmission.
Schnetzinger M, Heger F, Indra A, Kimberger O. J Hosp Infect 2023:S0195-6701(23)00203-7. Doi : 10.1016/j.jhin.2023.06.018.