Canadian company releases Legionella sampling study results

A Canadian company, Spartan Bioscience, recently released results of a Canadian study into on site Legionella testing.

It made some interesting findings:

  • 8% of cooling towers tested positive for Legionella DNA levels
  • On-site Legionella DNA testing was significantly more accurate than shipping water samples to a laboratory for Legionella culture testing. This finding was consistent with previous research. For example, the USA Centers for Disease Control and Prevention (CDC) found that Legionella culture underestimated actual levels by a factor of 10 or more.
  • The CDC also found culture incorrectly reported that water samples were negative for Legionella when in fact they were positive an average of 11.5 percent of the time.
  • Weekly on-site Legionella DNA testing was able to rapidly detect when Legionella bacteria grew to a higher action level. The doubling time of Legionella bacteria is typically between 22–72 hours in water systems and the natural environment. However, the doubling time at an “amplifier site” (such as a cooling tower) can be as few as 2.5 hours.
  • Overall, weekly testing is important because Legionella can reach high levels within days.

These results show the importance of being in control of your cooling system and that your control measures are always in place. A quality Written Scheme can help you manage these identify and control these measures as well as being a requirement of L8 and HSG 274 Part 1.

If you need help with your cooling system Collaton Consultancy can offer help and advice in managing your water treatment company and your control systems and processes.

Contact us on or phone on +44 (0)7958 124563.


Tests sponsored by PSPC showing high legionella levels may be unreliable, says PSPC

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