Reusable terminal tap water filters for nosocomial legionellosis prevention

Hospital water supplies often contain Legionella spp. and therefore represent a source of nosocomial infection especially for immunocompromised patients in intensive care or organ transplant units. Therefore, pathogen-free water should be provided for the care of these patients. Approaches of long-term Legionella spp. eradication from the plumbing system are rarely successful. Exposition prophylaxis might be another reasonable approach in high-risk patient care. To investigate the ability to provide water free of Legionella spp. with reusable water filters, a surveillance of splash water samples was performed. After determining the burden of Legionella spp. in the plumbing system of a paediatric oncological ward by ten unfiltered splash water samples, ten designated water taps were provided with terminal tap water filters that could be reprocessed by thermal disinfection. A further 129 samples were taken after a usage interval of 7 days and 10 more samples after a usage interval of 21 days before reprocessing the filters. All samples were checked for growth of Legionella spp. as well as other pathogenic bacteria. A total germ count of all samples was also performed. Half of the unfiltered splash water samples revealed growth of Legionella spp. All filtered water samples remained free of Legionella. Total germ count did not increase before a usage interval of 7 days. We believe the water filters tested are suitable for prevention of nosocomial legionellosis when reprocessed after 7 days as recommended by the manufacturer. To avoid retrograde contamination of filters, education of staff and patients in handling these devices is mandatory.