Legionella contamination of a cold-water supplying system in a German university hospital – assessment of the superheat and flush method for disinfection: Heat and flush disinfection for legionella contamination
Introduction: Legionella spp. is a potential pneumonia causing pathogen, which can be transmitted to humans from water-supplying systems. Immunocompromised but also healthy individuals can be vitally threatened. Both, hot and cold-water supplying systems must be considered as transmission sources and therefore a periodic surveillance has to be performed in public buildings according to local legislations. During a routine surveillance, a hazardous colonization was detected within the cold-water supplying system at University Hospital Knappschaftskrankenhaus Bochum, Germany. Applied architectural measures remained unsatisfying in the reduction of legionella contamination of the cold-water distributing system. Methods: Adapted to an analysis of risks, effort and benefit, the superheat and flush procedure was applied twice with a time interval of 6 months. Results were evaluated concerning the efficiency and the sustainability and statistically analyzed. 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.