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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

Published online by Cambridge University Press:  28 November 2019

Stephanie Thomas,
David Stevenson,
Akaninyene A. Otu,
Pascalis Vergidis,
Julian Barker,
Alan Ashworth,
Paul Exton,
Malcolm Richardson,
Ryan George and
Ginny Moore
Stephanie Thomas
Affiliation:
Department of Microbiology, Wythenshawe Hospital, Manchester University Foundation NHS Trust, Manchester, United Kingdom
David Stevenson
Affiliation:
Biosafety, Air and Water Microbiology Group, National Infection Service, PHE Porton, Porton Down, Salisbury, United Kingdom
Akaninyene A. Otu*
Affiliation:
The National Aspergillosis Centre, Wythenshawe Hospital, Manchester, University NHS Foundation Trust, Manchester, United KingdomDepartment of Internal Medicine, University of Calabar, Calabar, Cross River State, Nigeria
Pascalis Vergidis
Affiliation:
The National Aspergillosis Centre, Wythenshawe Hospital, Manchester, University NHS Foundation Trust, Manchester, United Kingdom
Julian Barker
Affiliation:
Cardiothoracic Anaesthesia and Intensive Care, Wythenshawe Hospital, Manchester, University NHS Foundation Trust, Manchester, United KingdomManchester University and Manchester Academic Health Science Centre, Manchester, United Kingdom
Alan Ashworth
Affiliation:
Department of Cardiothoracic Surgery, Wythenshawe Hospital, Manchester, University NHS Foundation Trust, Manchester, United Kingdom
Paul Exton
Affiliation:
Extracorporeal Membrane Oxygenation Unit, Wythenshawe Hospital, Manchester University Foundation NHS Trust, Manchester, United Kingdom
Malcolm Richardson
Affiliation:
NHS Mycology Reference Centre Manchester, Manchester University NHS Foundation Trust (Wythenshawe Hospital), Manchester, United KingdomDivision of Infection, Immunity & Respiratory Medicine, School of Biological Sciences, The University of Manchester, Manchester, United Kingdom
Ryan George
Affiliation:
Manchester University NHS Foundation Trust, Manchester, United Kingdom
Ginny Moore
Affiliation:
Biosafety, Air and Water Microbiology Group, National Infection Service, PHE Porton, Porton Down, Salisbury, United Kingdom
*
Author for correspondence: Akaninyene Otu, The National Aspergillosis Centre, Wythenshawe Hospital, Manchester, University NHS Foundation Trust, Manchester M23 9LT, UK. Email: akanotu@yahoo.com
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Abstract

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Information

Type
Research Brief
Information
Infection Control & Hospital Epidemiology , Volume 41 , Issue 2 , February 2020, pp. 242 - 244
Copyright
© 2019 by The Society for Healthcare Epidemiology of America. All rights reserved.

Heater-cooler units (HCUs) used in cardiopulmonary bypass and extracorporeal membrane oxygenation (ECMO) can generate infectious aerosols containing Mycobacterium chimaera, a slow-growing nontuberculous mycobacterium (NTM) associated with disseminated infection. Since the identification of M. chimaera infective endocarditis in 2013, many more cases of deep-seated infections with M. chimaera have been identified and linked to the use of contaminated Stöckert 3TLivaNova (London, United Kingdom) HCUs.Reference Van Ingen, Kohl and Kranzer1 Few studies have analyzed the water contamination of HCUs used in ECMO.Reference Trudzinski, Schlotthauer and Kamp2 In this study, we aimed to ascertain whether HICO-Variotherm units (Chalice Medical, Worksop, UK) used in ECMO were colonized with Mycobacterium spp and to assess the associated risk of aerosolization into the critical care environment.

Methods

Study setting

This investigation was conducted in the cardiothoracic critical care unit (CTCCU) of Wythenshawe hospital (Manchester, UK) which is a conventionally ventilated unit (ie, no HEPA filters). At the time of study (November 2017), 3 HICO-Variotherm HCUs (Chalice Medical) were in use for patients undergoing veno-venous ECMO for 7–15 days for severe respiratory failure (Fig. 1).

Fig. 1.

A heater cooler device.

Water samples

In the CTCCU, filtered tap water is used for the HCUs and water testing is not routinely performed. A serological pipette was used to transfer a sample (100 mL) of the water circulating through each HCU to a sterile sample container. Each water sample was cultured on tryptone soya agar (TSA; Oxoid, Basingstoke, UK), and potential marker organisms were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS). To culture for Mycobacterium spp, a 50-mL aliquot of each water sample was decontaminated and neutralized (BBL Mycoprep system, Becton Dickinson, Oxford, UK) before being passed through a 0.2-µm membrane filter. Each filter was transferred to a Middlebrooks 7H11 agar plate and incubated at 37°C for up to 6 weeks. To provide a more rapid indication of the presence or absence of Mycobacterium spp, each water sample was also assayed using an in-house quantitative polymerase chain reaction (qPCR) assay incorporating previously published primers.Reference Bruijnesteijn van Coopenraet, Lindeboom and Prins3 A qPCR assay was also used to detect the presence of Legionella spp using a method validated in a previous study.Reference Collins, Jorgensen and Willis4

Air samples

Air samples were collected immediately adjacent to each HCU and at the bedside (∼1 m from the unit). We used two types of air samplers. First, we used an impaction sampler (AirIdeal, bioMérieux UK Limited, Basingstoke, UK), in which airborne microorganisms are impacted on the surface of an agar plate. At each position, 3 consecutive samples were taken, each incorporating a different culture media: TSA, cetrimide agar (for Pseudomonas aeruginosa), or Middlebrooks 7H11. On each occasion, the sampler was operated at 100 L per minute for 5 minutes (sample volume, 0.5 m3 of air).

Second, we used a liquid impinger (Coriolis µ, Bertin Instruments, France), in which airborne microorganisms are concentrated in a collecting fluid. The sampler was operated once (300 L per minute for 10 minutes or 3 m3 of air) at each position, and the collecting fluid (phosphate buffered saline + 0.01% Tween 20) was cultured (in duplicate) on TSA, cetrimide agar, and Middlebrook 7H11 agar plates. Each plate was assayed for the presence or absence of Mycobacterium spp and Legionella spp using qPCR.

Water and air samples were obtained on the same day. The presence of organisms in both would imply contamination of the HCU with associated aerosolization into the surrounding clinical environment.

Results

Water samples

A single water sample was taken from each of the 3 ECMO units. The number of bacteria cultured (on TSA) ranged from 5.7 × 106 CFU/L to 3.8 × 107 CFU/L (n = 3). In all cases, the predominant organism was identified as Ralstonia spp (ie, picketti or insidiosa). No NTM were cultured from the water samples. However, when analyzed via qPCR Mycobacterium spp were detected in water taken from 2 of the 3 ECMO units at a level of 10.2 GU/L (the theoretical equivalent of 3.4 × 103 GU/L water) and 14.6 GU/3mL (∼4.8 × 103 GU/L water) (Table 1). A Legionella spp was detected in water taken from 2 of the 3 ECMO units at a mean concentration of 80.9 GU/3mL (∼3.4 × 104 GU/L water; n = 2) and 1,029 GU/3mL (∼3.4 × 105 GU/L water; n = 2). Legionella pneumophila was not detected.

Table 1.

Organisms Cultured From Water Collected From All 3 ECMO Units

Note. ECMO, extracorporeal membrane oxygenation; qPCR, quantitative polymerase chain reaction.

Air samples

Neither Ralstonia spp nor Mycobacterium spp were cultured from any of the 12 air samples (Table 1). Mycobacterium spp was not detected in any of the 6 air samples analyzed via PCR. Legionella pneumophila was detected in 1 air sample (86 GU/m3). The organism could not be cultured from the sample, so viability (or source) could not be confirmed.

Discussion

Mycobacteria chimaera produces biofilm that enables it to persist in water systems and its hydrophobicity favors aerosolization.Reference Walker, Moore and Collins5 In our study, we detected Mycobacteria spp in 2 of 3 ECMO water samples. However, unlike previous studies on HCUs used for cardiothoracic bypass, aerosolization into the environment was not demonstrated.

The Ralstonia genus is a group of gram-negative nonfermenters that are well adapted to surviving in low nutrient conditions, which allows them to persist in various water supplies.Reference Safni, Cleenwerck and De Vos6 We found high numbers of Ralstonia spp in the water circulating the ECMO units but none in associated air samples.

The ECMO machines are air-tight and closed systems in contrast to the HCUs used in cardiothoracic surgery, which may have precluded the release of aerosols.Reference Struelens and Plachouras7Mycobacteria chimaera contamination of ECMO devices was reported by Trudzinki et al.Reference Trudzinski, Schlotthauer and Kamp2 As in our study, they did not find any mycobacteria in the 9 room air samples or other environmental samples. Although transmission of M. chimaera from an ECMO device to a patient is yet to be described, the theoretical risk of aerosolization remains when machines are decontaminated or emptied or when circuits are broken during use. Regular and effective decontamination of the HCUs and microbiological surveillance are vital steps in mitigating the risk of infection due to M. chimera and other opportunistic pathogens.

Acknowledgments

We are grateful to the staff of the Extracorporeal Membrane Oxygenation (ECMO) unit of Wythenshawe Hospital for supporting this research.

Financial support

No financial support was provided relevant to this article.

Conflicts of interest

All authors report no conflicts of interest relevant to this article.

References

Van Ingen, J, Kohl, TA, Kranzer, K, et al.Global outbreak of severe Mycobacterium chimaera disease after cardiac surgery: a molecular epidemiological study. Lancet Infect Dis 2017;17:1033–1041.CrossRefGoogle ScholarPubMed
Trudzinski, FC, Schlotthauer, U, Kamp, A, et al.Clinical implications of Mycobacterium chimaera detection in thermoregulatory devices used for extracorporeal membrane oxygenation (ECMO), Germany, 2015 to 2016. Euro Surveill 2016;21:1–8.CrossRefGoogle Scholar
Bruijnesteijn van Coopenraet, ES, Lindeboom, JA, Prins, JM, et al.Real-time PCR assay using fine-needle aspirates and tissue biopsy specimen for rapid diagnosis of mycobacterial lymphadenitis in children. J Clin Micro 2004;42:2644–2650.CrossRefGoogle Scholar
Collins, S, Jorgensen, F, Willis, C, et al.Real-time PCR to supplement gold-standard culture-based detection of Legionella in environmental samples J Appl Microbiol 2015;119:1158–1169.CrossRefGoogle ScholarPubMed
Walker, J, Moore, G, Collins, S, et al.Microbiological problems and biofilms associated with Mycobacterium chimaera in heater-cooler units used for cardiopulmonary bypass. J Hosp Infect 2017;96:209–220.CrossRefGoogle ScholarPubMed
Safni, I, Cleenwerck, I, De Vos, P, et al.Polyphasic taxonomic revision of the Ralstonia solanacearum species complex: proposal to emend the descriptions of Ralstonia solanacearum and Ralstonia syzygii and reclassify current R. syzygii strains as Ralstonia syzygii subsp. syzygii subsp. nov., R. solanacearum phylotype IV strains as Ralstonia syzygii subsp. indonesiensis subsp. nov., banana blood disease bacterium strains as Ralstonia syzygii subsp. celebesensis subsp. nov., and R. solanacearum phylotype I and III strains as Ralstonia pseudosolanacearum sp. nov. Int J Syst Evol Microbiol 2014;64:3087–3103.CrossRefGoogle Scholar
Struelens, MJ, Plachouras, D.Mycobacterium chimaera infections associated with heater-cooler units (HCU): closing another loophole in patient safety. Euro Surveill 2016;21:30397.CrossRefGoogle ScholarPubMed
Figure 0

Fig. 1.A heater cooler device.

Figure 1

Table 1.Organisms Cultured From Water Collected From All 3 ECMO Units