Contamination of public whirlpool spas: factors associated with the presence of Legionella spp., Pseudomonas aeruginosa and Escherichia coli

This work explores the factors associated with contamination of public spas by Legionella spp., Pseudomonas aeruginosa and Escherichia coli. Physicochemical and microbiological parameters were measured in water samples from 95 spas in Quebec, Canada. Spa maintenance was documented by a questionnaire. Legionella spp. were detected in 23% of spas, P. aeruginosa in 41% and E. coli in 2%. Bacteria were found in concerning concentrations (Legionella spp. >= 500 CFU/l, P. aeruginosa > 51 CFU/100 ml or E. coli > 1 CFU/100 ml) in 26% of spas. Observed physicochemical parameters frequently differed from recommended guidelines. The following factors decreased the prevalence of concerning microbial contamination: a free chlorine concentration >= 2 mg/l or total bromine >= 3 mg/l (p = 0.001), an oxidation-reduction potential (ORP) > 650mV (p = 0.001), emptying and cleaning the spa at least monthly (p = 0.019) and a turbidity <= 1 NTU (p = 0.013). Proper regulations and training of spa operators are critical for better maintenance of these increasingly popular facilities.