Efficacy of Slightly Acidic Electrolyzed Water (SAEW) Comparing to Chlorine on Inactivation of Legionella Pneumophila Isolated from Drinking Water Tanks

Legionella is an opportunistic waterborne pathogen which is transmitted to humans via inhalation of contaminated water droplets. In addition, Legionella pneumophila is considered ubiquitous bacterium which inherently resistant to chlorine in tap water. On the other side, recent researches revealed that SAEW is considered a novel sanitizer against a broad spectrum of bacteria and possesses nonselective antimicrobial properties. A total of 300 drinking water samples were collected from water tanks (100 samples from hotels, 100 samples from plants and 100 samples from residential units) at Alexandria and Cairo governments from January till July 2023. Results revealed that the incidence of Legionella species in drinking water samples from hotels, plants and residential units water tanks were 0 % (0/100) , 3 % (3/100) and 1% (1/100), respectively. Two isolates from plants water tanks were identified as Legionella pneumophila by RT PCR. The efficacy of slightly acidic electrolyzed water (SAEW) was assessed comparing to chlorine on inactivation and biofilm adherence strength of Legionella pneumophila isolates. The obtained results showed that SAEW was more effective on inactivation of the two Legionella pneumophila isolates than chlorine within shorter treatment duration, where 100 % inactivation of Legionella pneumophila achieved after 3 hrs and 48 hrs from SAEW and chlorine treatment, respectively. In addition, SAEW showed significant effect on the biofilm adherence strength of the two Legionella pneumophila isolates. This study underlines the highly antimicrobial effect of SAEW on inactivation of Legionella within short duration without any undesirable residual agents in water which may cause further water pollution.