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Edinburgh Legionnaires’ outbreak: Cooling towers ‘likely’ source

Well, investigations of Legionella outbreaks always seem to involve a combination of microbiology and building science so I thought I would post this link here: BBC News – Edinburgh Legionnaires’ outbreak: Cooling towers ‘likely’ source.  I wonder how much Legionella is showing up in other buildings – especially in DNA based surveys – even when people are not getting sick.  Where does it lurk?  How does it get around?

5 thoughts on “Edinburgh Legionnaires’ outbreak: Cooling towers ‘likely’ source

  1. Legionella has been shown to be a common isolate from potable water distribution systems, including hospital shower heads and water taps in patient rooms, particularly in rooms which have been unoccupied recently. In addition, Legionella have been isolated in a European study from roadside puddles after a rainstorm. They are likely more widely distributed then first thought. Both the EU and Australia mandate regular testing of cooling towers for Legionella, and specify trigger limits for a disinfection response. No such mandate exists in the USA, although the CDC, ASHRAE (American Society of Heating, Refrigeration, and Air Conditioning Engineers), and the CTI (Cooling Tower Institut e)do have suggested guidelines.

    1. If you read the ASHRAE standards’, testing for Legionella is not mandated; rather the stress is placed on prevention and proper maintenance of your plumbing systems and cooling towers. Testing for legionella is difficult can easily be missed. In the event that legionella was found in a cooling tower, it still does not mean anything as these bacteria could be dead already from the biocides being used to kill them. The only way to truly test for them is to culture them and that takes 30 days minimum and leaves the public at risk.

      1. Jon: you are correct in that the ASHRAE standards do not mandate testing; neither does the CTI or CDC documents because a mandate can only come from legislative/lawmaking bodies. Testing is suggested, though, otherwise how to know if you have a problem? Viable testing at contract labs (for example, Biosan) has a turnarond time of less then three weeks, and there are both PCR and antibody-based tests available for rapid determination for the presence of pathogenic (serotype 1) Legionella, although, as you point out, they are not indicative of viable pathogens. However, if you have a presumptive positive (rapid) test and a heavily-fouled tower with abundant biofilm, a reasonable person should be thinking about treating that tower as if it had Legionella.

  2. I believe one of the problems with Legionella in particular is that there are many species and serotypes of Legionella, only some of which have pathogenic potential. So it’s very likely that the genus is indeed widespread but in rRNA and metagenomic surveys we aren’t getting enough information to know anything about risk. I believe that the screening in Europe is PCR-based and therefore focuses on the known pathogenic serotypes.

  3. Cooling tower condenser systems are designed to throw out the heat from the medium (usually water) used to condense refrigerant gas in either an open-circuit or closed-circuit configuration. Condencers and cooling towers are the most common kinds of heat rejection equipment. Condensers remove heat from the refrigeration system, like the evaporator, the condenser is a heat trasfer device.We are prominent global cooling tower manufacturerthat uses the finest quality raw material and advanced technology in production process, to ensure that the products manufactured at our end are durable and are in adherence with the international quality standards. Our organization has collaboration with engineers, skilled and semi-skilled professionals in order to provide the best quality products and services as per client’s need that truly reflects our dedication towards our job. We are trying to maintain long term relationship with our clients and thus we offer them quality services.

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