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Microbial contamination of heater cooler units used in extracorporeal membrane oxygenation is not aerosolized into the environment: A single-center experience

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Abstract

Microbial contamination of heater cooler units used in extracorporeal membrane oxygenation is not aerosolized into the environment: A single-center experience - Stephanie Thomas, David Stevenson, Akaninyene A. Otu, Pascalis Vergidis, Julian Barker, Alan Ashworth, Paul Exton, Malcolm Richardson, Ryan George, Ginny Moore

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... The isolation of Legionella spp. from several HCUs [28,34,35] has raised concern that also these pathogens may be transmitted to the surgical staff through aerosolization of the water contained in these devices. While it is unlikely that respiratory exposure to Legionella from HCUs occurs in patients undergoing cardiothoracic surgery due to the closed-circuit ventilation of these units, there is also a theoretical risk of exposure to Legionella-containing aerosols for same-unit patients that are not being kept on closed circuit ventilation. ...
... This study is the first to quantify Legionella in HCUs and HU35 devices using the PMA-qPCR method. Previous reports assessed the extent of Legionella contamination in thermoregulatory devices using either bacterial culture [28] or PCR [35], with the latter method being used to examine three devices only. In our study, besides analyzing a much larger number of devices from numerous regional hospitals, we were able to inhibit PCR amplification of DNA from dead cells by including PMA treatment in our protocol, which allowed us to obtain a Legionella recovery rate of 65.2%. ...
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Culture remains the gold-standard for the enumeration of environmental Legionella. However, it has several drawbacks including long incubation and poor sensitivity, causing delays in response times to outbreaks of Legionnaires' disease. This study aimed to validate real-time PCR assays to quantify Legionella species (ssrA gene), Legionella pneumophila (mip gene) and L. pneumophila serogroup-1 (wzm gene) to support culture-based detection in a frontline public health laboratory. Each qPCR assay had 100% specificity, excellent sensitivity (5 GU/reaction) and reproducibility. Comparison of the assays to culture-based enumeration of Legionella from 200 environmental samples showed that they had a negative predictive value of 100%. Thirty eight samples were positive for Legionella species by culture and qPCR. One hundred samples were negative by both methods whereas 62 samples were negative by culture but positive by qPCR. The average log10 increase between culture and qPCR for Legionella spp. and L. pneumophila was 0.72 (p = 0.0002) and 0.51 (p = 0.006) respectively. The qPCR assays can be conducted on the same 1L water sample as culture thus can be used as a supplementary technique to screen out negative samples and allow more rapid indication of positive samples. The assay could prove informative in public health investigations to identify or rule out sources of Legionella as well as to specifically identify L. pneumophila serogroup 1 in a timely manner not possible with culture. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.