The Battle against Legionella. Disinfection in Manmade Water Systems: A Systematic Review

Author(s): Venia Stavrou, Ioanna Chatziprodromidou, Apostolos Vantarakis

Legionella constitutes the main cause of Legionnaires’ disease (LD), a severe multisystem illness and life-threatening pulmonary infection. Manmade water systems are the main source of infection. Finding the most effective method is a matter of utmost importance. We conducted a systematic review to evaluate the effectiveness of disinfection methods against Legionella and the frequency of use of these methods. We recorded Legionella species and serogroups that are usually detected in manmade water systems, the building types and water systems where Legionella constitutes a problem. Literature search was conducted in two databases. Data were extracted from 141 studies that finally met the inclusion criteria. According to these studies, disinfection methods in manmade water systems were applied 259 times and the corresponding registrations were conducted in the data extraction form. Legionella pneumophila was the most common species detected in manmade water systems and Legionella pneumophila serogroup 1 the most common serogroup. The majority of studies dealt with Legionella in hospitals and in hot and cold water systems. Chemical disinfection methods had longer duration, while the combination of physical and chemical disinfection methods was more effective. Point – of – use filters, Cooper silver ionization and Hydrogen peroxide proved to be the most effective methods. Cooper silver ionization had the lowest percentage of Legionella concentration increase, while ultraviolet light had a temporary duration of effectiveness against Legionella in the water system. No disinfection method has a 100% reduction of Legionella concentration, 100% decrease of colonized sites and duration of effectiveness all at the same time.