1.7 Factors that influence growth Legionella Various factors that influence and promote growth have been identified Legionella since its initial identification back in 1976. 1.7.1 Physio-chemical factors can survive extreme ranges of environmental conditions. It can survive Legionella temperatures of 0ºC to 63ºC and has been found in waters at temperatures between 5ºC and 63ºC but significantly more has been isolated from warm waters at Legionella temperatures of 30ºC and above. can also survive a wide pH range of Legionella 8.5 and a dissolved oxygen concentration in water of 0.2 to 15 mg/l. L. pneumophila grows best at a pH of 5.5 to 6.2 with an oxygen concentration of 6.0 to 6.2 mg/l. However, species were found in an extremely acidic, predominantly Legionella eukaryotic algal biofilm community in Yellowstone National Park, US, at a pH as low as 2.7. Small concentrations of salt (NaCl 0.1 to 0.5%) may also enhance the survival of and it has been found in cooling systems using seawater (Fliermans Legionella et 1981, Nguyen 1991, Lee and West, 1991, Newsome, 2001, Sheenan al., et al.,. et al., 2005). Metal plumbing components and associated corrosion products are also important factors as these can provide iron and other metals that support the survival and growth of in plumbing systems (States 1985). Legionella et al., 1.7.2 Microbial factors The growth and survival of is affected by the presence of other organisms. Legionella Studies have demonstrated that were incapable of growing in sterile water Legionella because it required nutrients supplied by other micro-organisms, including bacteria (Wadowsky and Yee, 1983), protozoa (Rowbottom, 1980), and (Tison cyanobacteria 1980). et al., Protozoa play an important role in the increase and spread of in Legionella anthropogenic water systems and therefore in the occurrence of Legionnaires’ disease (DeClerck 2009). can infect and grow, similar as with macrophages, et al., Legionella 13
1.7 Factors that influence Legionella growth Various factors that influence and promote Legionella growth have been identified since its initial identification back in 1976. 1.7.1 Physio-chemical factors Legionella can survive extreme ranges of environmental conditions. It can survive temperatures of 0ºC to 63ºC and has been found in waters at temperatures between 5ºC and 63ºC but significantly more Legionella has been isolated from warm waters at temperatures of 30ºC and above. Legionella can also survive a wide pH range of and a dissolved oxygen concentration in water of 0.2 to 15 mg/l. L. pneumophila grows best at a pH of 5.5 to 6.2 with an oxygen concentration of 6.0 to 6.2 mg/l. However, Legionella species were found in an extremely acidic, predominantly eukaryotic algal biofilm community in Yellowstone National Park, US, at a pH as low as 2.7. Small concentrations of salt (NaCl 0.1 to 0.5%) may also enhance the survival of Legionella and it has been found in cooling systems using seawater (Fliermans et al., 1981, Nguyen et al.,. 1991, Lee and West, 1991, Newsome, 2001, Sheenan et al., 2005). Metal plumbing components and associated corrosion products are also important factors as these can provide iron and other metals that support the survival and growth of Legionella in plumbing systems (States et al., 1985). 1.7.2 Microbial factors The growth and survival of Legionella is affected by the presence of other organisms. Studies have demonstrated that Legionella were incapable of growing in sterile water because it required nutrients supplied by other micro-organisms, including bacteria (Wadowsky and Yee, 1983), protozoa (Rowbottom, 1980), and cyanobacteria (Tison et al., 1980). Protozoa play an important role in the increase and spread of Legionella in anthropogenic water systems and therefore in the occurrence of Legionnaires’ disease (DeClerck et al., 2009). Legionella can infect and grow, similar as with macrophages, 13 8.5
Birgitta-Bedford-Thesis-2012.docx