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Chapter 131 : Environmental Sampling Data to Determine Risk: a United Kingdom Perspective
This chapter presents the panel responses to questions posed to the round table discussion “Environmental Sampling Data to Determine Risk". A risk assessment (RA) should be carried out in all premises that have public access and should include all healthcare premises, factories and office blocks. An RA should include a thorough site survey for all water systems in use, cooling towers, hot and cold water systems, spa pools, irrigation systems and should take into account the population using the premises. PCR can be used with the following provisos: there are still some issues around the sensitivity and specificity of PCR for legionellae, especially around the target sequences for the genus. The problems associated with thermostatic mixing valves (TMVs) are mainly associated with the fact that the temperature downstream of these is within the ideal range for microbial growth. A period of intensive monitoring should be undertaken including aerobic colony counts (not dipslides) combined with Legionella testing, ideally using both culture and PCR. The ecological determinants of Legionella colonization are common to all systems. Temperature, nutrients, presence of other microorganisms, and stagnation are all major predictors of Legionella growth. As a result, ecological determinants can be readily standardized across a wide range of systems, but risk assessment cannot.