Legionella sampling

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Legionella sampling

  1. 1. LegionellaSamplingCulture v PCR - By Nemco Utilities(www.nemco-utilities.co.uk)
  2. 2. Nemco Utilities LimitedLegionella SamplingCulture v PCRThe gold standard for Legionella testing has alwaysbeen the culture method (often referred to as thestandard reference method) whereby the bacteria arefiltered from a water sample, grown and then thenumber of colony forming units (cfu) estimated.However, this is a labour intensive process with a 12 dayturnaround. Given the penalties for non-complianceand costs associated with taking water services out ofuse for 12 days, the culture method is rapidly becomingoutdated. For more information about Legionella sampling or managing the risks associated with Legionella, please contact Nemco Utilities at www.nemco-utilities.co.uk
  3. 3. Nemco Utilities LimitedLegionella SamplingCulture v PCRA number of recent scientific advances haverevolutionised the face of Legionella analysis and now,with a decent courier, samples can be turned around in24 hours (4 in an emergency). Progress has been madepossible due to the use of Polymerase Chain Reaction(PCR) technology. Rather than actually growing theLegionella bacteria, PCR works by isolating fragments ofDNA from the water sample and amplifying them to adetectable level. This process is a lot quicker, moreefficient and can largely be automated. For more information about Legionella sampling or managing the risks associated with Legionella, please contact Nemco Utilities at www.nemco-utilities.co.uk
  4. 4. Nemco Utilities LimitedLegionella SamplingCulture v PCRPCR has been of inestimable value especially for trendanalysis and when investigating outbreaks. It is notwithout its problems. The initial stumbling block was thatof detecting ‘dead’ or ‘non viable’ cells, that would notshow up on culture. This has since been largelyovercome, but PCR in general terms still returns far morepositive results than the culture method. This leads on tothe next problem of reporting units and their correlationwith action levels. For more information about Legionella sampling or managing the risks associated with Legionella, please contact Nemco Utilities at www.nemco-utilities.co.uk
  5. 5. Nemco Utilities LimitedLegionella SamplingCulture v PCRThe current Legionella guidance ACOP L8 containsrecommendations for ‘Action in the event of a positivesample’ as below (for domestic water systems):Legionella bacteria (cfu/ ACTION REQUIRED (L8)litre)More than 100 but less than Details >>1000More Than 1000 Details >> For more information about Legionella sampling or managing the risks associated with Legionella, please contact Nemco Utilities at www.nemco-utilities.co.uk
  6. 6. Nemco Utilities LimitedLegionella SamplingCulture v PCRLegionella bacteria (cfu/ litre) ACTION REQUIRED (L8)More than 100 but less than Either:1000 (a) If only one or two samples are positive, system should be re-sampled. If a similar count is found again, a review of the control measures and risk assessment should be carried out to identify any remedial actions. For more information about Legionella sampling or managing the risks associated with Legionella, please contact Nemco Utilities at www.nemco-utilities.co.uk
  7. 7. Nemco Utilities LimitedLegionella SamplingCulture v PCRLegionella bacteria (cfu/ litre) ACTION REQUIRED (L8)More than 100 but less than (b) If the majority of samples1000 are positive, the system may be colonised, albeit at a low level, with legionella. Disinfection of the system should be considered but an immediate review of control measures and risk assessment should be carried out to identify any other remedial action required. For more information about Legionella sampling or managing the risks associated with Legionella, please contact Nemco Utilities at www.nemco-utilities.co.uk
  8. 8. Nemco Utilities LimitedLegionella SamplingCulture v PCRLegionella bacteria (cfu/ litre) ACTION REQUIRED (L8)More than 1000 The system should be re- sampled and an immediate review of the control measures and risk assessment carried out to identify any remedial actions, including possible disinfection of the system. For more information about Legionella sampling or managing the risks associated with Legionella, please contact Nemco Utilities at www.nemco-utilities.co.uk
  9. 9. Nemco Utilities LimitedLegionella SamplingCulture v PCRThe reporting units in this table refer entirely to colonyforming units (cfu), whereas PCR sample results arereturned in genomic units (GU). Therefore, if we get anegative culture test but a positive PCR test – whataction to take? Or similarly, if PCR is used in isolation atwhat point do you start spending large amounts ofmoney disinfecting water systems and taking servicesout of action? There is no way of correlating the twounits and no set levels for genomic units. For more information about Legionella sampling or managing the risks associated with Legionella, please contact Nemco Utilities at www.nemco-utilities.co.uk
  10. 10. Nemco Utilities LimitedLegionella SamplingCulture v PCRCurrently a large number of companies offering PCR,back up the results with a culture test (at extra cost). It iscertainly in no doubt that future analysis will movetowards PCR (molecular photocopying as it issometimes known). In the meantime, we will be lookingto the HSE for guidance on the newly UKAS accreditedPCR testing method. For more information about Legionella sampling or managing the risks associated with Legionella, please contact Nemco Utilities at www.nemco-utilities.co.uk
  11. 11. Nemco Utilities LimitedContact DetailsAddress Email:Nemco Utilities Ltd  info@nemco-12 Kempson Way utilities.co.ukHillside Business Park  sales@nemco-Bury St Edmunds utilities.co.ukSuffolk  accounts@nemco-IP32 7EA utilities.co.uk Website:Telephone: 01284 724503 http://www.nemco-Fax No.: 01284 724826 utilities.co.uk/ For more information about Legionella sampling or managing the risks associated with Legionella, please contact Nemco Utilities at www.nemco-utilities.co.uk

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