S4: Emerging issues in Legionella control

Since its identification, as the cause of Legionnaires disease, control of Legionella in cooling waters has acquired increasing significance.  Recent research focuses have been in areas pertaining to its mode of infection and ability to survive within human alveolar macrophages. The availability of superior monitoring techniques, including molecular probes, have shown the problem to be far more prevalent than originally perceived and extends to many more manmade microbe harboring niches such as shower heads, spas, water fountains, domestic plumbing, garden soil and extends to wherever aerosolization of water can take place. Many organizations, around the world, including CDC and WHO, have recommendations for controlling the spread of Legionella pneumophila and affected industry bodies have come up with guidelines for best practices. While research efforts have implicated the usual culprits such as under-dosing, protective effects of multi-species biofilms, there is clear evidence that the current practices used for Legionella control need further refinements.  The amplification of Legionella by amoeba predators renders this family of organisms relatively recalcitrant to conventional doses of biocides. This talk will summarize the impact of emerging guidelines and alternatives that are currently being evaluated by the cooling tower industry and speculate on areas for future developments.