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legionella. The authors concluded that the elevated water age inherent to achieving the sustainability goals of plumbing systems in green buildings raised concerns with respect to the chemicals and microbiological stability of the water quality.
• Donohue et al.( 2014) used two qPCR assays to evaluate incidence of L. pneumophila serogroup 1 in 272 water samples collected in 2009 and 2010 from 68 public and private cold drinking water taps across the United States. L. pneumophila serogroup 1 was detected in 47 % of the taps.
• Stout et al.( 2007) isolated L. pneumophila and L. anisa from 14 hospital water systems. They observed high-level colonisation of the premise plumbing system( defined as 30 % or more of the distal outlets being positive for L. pneumophila) for six of the 14 hospitals with positive findings.
• Borella et al.( 2005b) studied legionella in hot water samples of 40 hotels in five Italian cities. They detected legionella in 30 hotels and 60.5 % of samples. L. pneumophila was found in 87 % of positive samples, and L. pneumophila serogroup 1 was in 45.8 % of positive samples. Of the samples positive for L. pneumophila serogroup 1, 75.8 % had concentrations of 1 000CFU / l( colony-forming units per litre) or more. The authors found that L. pneumophila serogroup 1 presence correlated with soft water and higher chlorine levels(> 0.1 milligrams per litre( mg / l)). They also noted that P. aeruginosa was less likely to occur at these chlorine levels and more likely to occur in hard water.
• Patterson et al.( 1997) sampled hot and cold-water outlets in 69 organ transplant units in the United Kingdom for legionella and protozoa. They found legionella in 55 % of units and L. pneumophila in 45 %. Other legionella( the blue – white fluorescent group, which includes L. gormanii, L. bozemanii and others) were detected in 26 % of organ transplant units. Protozoa of genera known to support growth of legionella were found in 58 % of units. The authors found a significant association between the detection of legionella and the presence of these protozoan genera in the cold-water outlets sampled.
• Wadowsky et al.( 1985), using tap water from their laboratory, found that naturally occurring L. pneumophila multiplied at a temperature between 25 and 37 ° C at pH levels of 5.5 – 9.2, and at concentrations of dissolved oxygen of 6.0 – 6.7mg / l. They also noted that legionella growth did not occur in tap water when the dissolved oxygen level was less than 2.2mg / l. They also observed an association between the multiplication of L. pneumophila and non-legionellaceae bacteria, which were also present in the water culture.
• Wadowsky et al.( 1982) sampled showerheads, shower pipes, and water and sediment collected from the bottom of hot water tanks in 11 buildings, including five homes and three hospitals. L. pneumophila serogroups 1, 5 and 6 were isolated from the drinking water fixtures in seven buildings, including one of the five homes. Legionella species were also present in water and sediment in hot water tanks maintained at temperatures from 39 to 54 ° C, but not found in tanks maintained between 71 and 77 ° C. The authors hypothesised that hot water tanks are the major source and seed of L. pneumophila in premise plumbing systems.
• Tobin et al.( 1981b) conducted a premise plumbing system survey of 31 buildings including hospitals and hotels, six of which were associated with sporadic cases or outbreaks of legionnaires’ disease. For the six buildings( hospitals and hotels) associated with cases of legionnaires’ disease, the study found L. pneumophila in all of the premise plumbing systems and in the cooling water for each of the three buildings with cooling towers. For buildings that had not previously experienced an outbreak, the study found L. pneumophila in four out of 24 taps or showers, three out of nine cooling towers, and one out of 15 storage tanks.
The growth of legionella within a premise plumbing system may be a function of the system’ s pipe or other plumbing materials, water temperature, water quality and other system-specific factors. Tai et al.( 2012) found that copper inhibited biofilm growth at temperatures typically found in hot water systems( 20, 37 and 44 ° C), whereas stainless steel and polyethylene promoted the development of biofilm and growth of L. pneumophila. Biofilm formation by L. pneumophila was found to be inhibited in iron-rich conditions( Hindré et al., 2008). Moritz et al.( 2010) found that L. pneumophila and P. aeruginosa penetrated biofilms grown in cold water on different plumbing materials in the laboratory: ethylene-propylene diene-monomer( EPDM) rubber, silane cross-linked polyethylene, electron ray crosslinked polyethylene, and copper. The pathogens, added to biofilms after 14 days, became part of the biofilms in EPDM and the polyethylenes; however, only L. pneumophila grew in the copper biofilm, and only in low numbers. In a study of eight different plumbing materials, latex and synthetic rubbers( ethylene-propylene) grew the most extensive biofilm, probably because these materials leach the most nutrients( Rogers et al., 1994).
Regulatory context EPA regulates legionella under the Surface Water Treatment Rule( SWTR). The SWTR has treatment technique requirements to control for Giardia and viruses. The SWTR’ s treatment technique requirements
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www. plumbingafrica. co. za February 2017 Volume 22 I Number 12