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. 2020 Nov 23;9(11):978.
doi: 10.3390/pathogens9110978.

Persistence of Legionella in Routinely Disinfected Heater-Cooler Units and Heater Units assessed by Propidium Monoazide qPCR

Savina Ditommaso  1 , Monica Giacomuzzi  1 , Gabriele Memoli  1 , Jacopo Garlasco  1 , Carla M Zotti  1
Affiliations

Persistence of Legionella in Routinely Disinfected Heater-Cooler Units and Heater Units assessed by Propidium Monoazide qPCR

Savina Ditommaso et al. Pathogens. .

Abstract

Background: Evidence to date indicates that heater-cooler units (HCUs) and heater units (HUs) can generate potentially infectious aerosols containing a range of opportunistic pathogens such as Mycobacterium chimaera, other non-tuberculous mycobacterial (NTM) species, Pseudomonas aeruginosa and Legionella spp. Our purpose was to determine the extent of Legionella contamination and total viable count (TVC) in HCUs and HUs and to analyze the relationship by water system design of devices of two different brands (LivaNova vs. Maquet).

Methods: Legionella spp. were detected and quantified by our optimized PMA-qPCR protocol; TVCs were assessed according to ISO protocol 6222. Analyses were performed in the first sampling round and after six months of surveillance.

Results: Overall, Legionella spp. was detected in 65.7% of devices. In the second sampling round, Legionella positivity rates were significantly lower in water samples from the Maquet devices compared to the LivaNova ones (27.3% vs. 61.5%). LivaNova HCUs also yielded more Legionella, and aquatic bacteria counts than Maquet in both first and second-round samples.

Conclusions: We recommend that all surgical patients and staff exposed to aerosols from thermoregulatory devices should be followed up for Legionella infection and that microbiological surveillance on such devices should be conducted regularly as precautionary principle.

Keywords: Legionella; NTM; heater–cooler unit; propidium monoazide qPCR.

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Conflict of interest statement

None of the authors declares to have a conflict of interest that could influence or bias the content of the paper.

Figures

Figure 1
Figure 1
Detailed description of heater–cooler units (HCU) devices: common features and differences (ventilators in red, water tank in blue, red dotted arrows representing airflow direction, blue dotted arrows representing potential direction of aerosol leakage) (source: Kuhel et al. 2018) [39].
Figure 2
Figure 2
Detailed description of HU35 devices. (Provided by Getinge).
Figure 3
Figure 3
Legionella spp. concentration in thermoregulatory devices water samples collected at the first sampling round. (a) and after six months of monthly disinfection at the second sampling round (b).
Figure 3
Figure 3
Legionella spp. concentration in thermoregulatory devices water samples collected at the first sampling round. (a) and after six months of monthly disinfection at the second sampling round (b).
Figure 4
Figure 4
TVC concentration in thermoregulatory devices water samples collected at the first sampling round. (a) and after six months of monthly disinfection at the second sampling round (b).
Figure 5
Figure 5
(a) Correlation between Legionella counts and TVC at 22 °C in the first sampling round. (b) Correlation between Legionella counts and TVC at 22 °C in the second sampling round.
See this image and copyright information in PMC

References

    1. Fields B.S., Benson R.F., Besser R.E. Legionella and Legionnaires’ disease: 25 years of investigation. Clin. Microbiol. Rev. 2002;15:506–526. doi: 10.1128/CMR.15.3.506-526.2002. - DOI - PMC - PubMed
    1. Hammami N., Laisnez V., Wybo I., Uvijn D., Broucke C., Van Damme A., Van Zandweghe L., Bultynck W., Temmerman W., Van De Ginste L., et al. A cluster of Legionnaires’ disease in Belgium linked to a cooling tower, August-September 2016: Practical approach and challenges. Epidemiol. Infect. 2019;147:e326. doi: 10.1017/S0950268819001821. - DOI - PMC - PubMed
    1. Paranjape K., Bédard É., Whyte L.G., Ronholm J., Prévost M., Faucher S.P. Presence of Legionella spp. in cooling towers: The role of microbial diversity, Pseudomonas, and continuous chlorine application. Water Res. 2020;169:115252. doi: 10.1016/j.watres.2019.115252. - DOI - PubMed
    1. Wüthrich D., Gautsch S., Spieler-Denz R., Dubuis O., Gaia V., Moran-Gilad J., Hinic V., Seth-Smith H.M., Nickel C.H., Tschudin-Sutter S., et al. Air-conditioner cooling towers as complex reservoirs and continuous source of Legionella pneumophila infection evidenced by a genomic analysis study in 2017, Switzerland. Euro Surveill. 2019;24 doi: 10.2807/1560-7917.ES.2019.24.4.1800192. - DOI - PMC - PubMed
    1. Cunha B.A., Burillo A., Bouza E. Legionnaires’ disease. Lancet. 2016;387:376–385. doi: 10.1016/S0140-6736(15)60078-2. - DOI - PubMed