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. 2021 Sep 15;62(3):E751-E758.
doi: 10.15167/2421-4248/jpmh2021.62.3.1944. eCollection 2021 Sep.

Legionella contamination of a cold-water supplying system in a German university hospital - assessment of the superheat and flush method for disinfection

Matthias Unterberg  1 , Tim Rahmel  1 , Thomas Kissinger  2 , Christian Petermichl  1   3 , Michael Bosmanns  3 , Martin Niebius  3 , Christina Schulze  3 , Hans-Peter Jochum  4 , Nina Parohl  5 , Michael Adamzik  1 , Hartmuth Nowak  1
Affiliations

Legionella contamination of a cold-water supplying system in a German university hospital - assessment of the superheat and flush method for disinfection

Matthias Unterberg et al. J Prev Med Hyg. .

Abstract

Introduction: In case of a contamination of water-supplying systems in hospitals with legionella, usually chemical disinfection measures are used for remediation. Unfortunately, it is reported, that these methods may not be sustainable, have an impact on water quality, and can even fail. As an alternative, the superheat and flush method does not need any special equipment, can be initiated in a short lead of time and does not affect the water quality. However, evidence on this disinfection measurement against legionella is lacking. We therefore investigated and report on the effectiveness and long-term results of the superheat and flush disinfection method.

Methods: During routine periodical examinations, a rising count of legionella was detected in the cold-water supplying system at a German university hospital. Adapted to an analysis of risks, effort and benefit, the superheat and flush procedure was applied twice within 6 months.

Results: While 33 out of 70 samples had a higher legionella count than the legal threshold of 100 CFU/100 mL (CFU - Colony Forming Units) before the first disinfection was carried out, this number could be reduced to 1 out of 202 samples after the first intervention. Additionally, in contrast to previously published studies, the effect was long-lasting, as no relevant limit exceedance occurred during the following observation period of more than two years.

Conclusion: The superheat and flush disinfection can provide an economic and highly effective measure in case of legionella contamination and should be shortlisted for an eradication attempt of affected water-supplying systems in hospitals.

Keywords: Hospital-acquired Legionnaires’; Legionella; Superheat and flush; Water-supplying system; disease.

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Conflict of interest statement

Conflict of interest statement The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Schematic representation of the cold-water supplying system at the study hospital (IOI: Interdisciplinary, operative ICU; MNI: Medical, neurological ICU meta-analysis).
Fig. 2.
Fig. 2.
Visualization of the sampling technique for determination of legionella colony forming units per 100 mL (MCE: mixed cellulose ester; BCYE: buffered charcoal yeast extract; GVPC: glycine, vancomycin, polymyxin and cycloheximide).
Fig. 3.
Fig. 3.
Distribution of Colony Forming Units (CFU) per 100 mL of Legionella spp. within the cold-water supplying system for a) all sampling points or b) only matched, identical sampling points, before/after superheat and flush disinfection. Horizontal line indicating the limit value of 100 CFU / 100 mL (IOI: interdisciplinary, operative ICU; MNI: medical, neurological ICU; PS2: pressure stage 2; PS3: pressure stage 3; #14+15: building no. 14 and 15; #12: building no. 12; * p-value < 0.05.; ** p-value < 0.001.
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