Dubai-based Advanced Biotechnology Centre (ABC) is the first private lab in the GCC region to employ DNA technique for Legionella detection
Dubai-based Advanced Biotechnology Centre (ABC) has become the only laboratory in the Gulf Co-operation Council (GCC) region certified to provide DNA technique for Legionella detection, following its ISO 17025 accreditation by the Dubai Accreditation Centre (DAC).
Legionella species which occur naturally in soil, rivers and lakes have the ability to successfully colonise man-made water handling and storage systems and HVAC systems. This colonisation, proliferation and subsequent circulation of the bacterium under ideal environmental conditions have raised concerns among Facility Management (FM) companies, the hotel industry and also common people aware of the potential health issues Legionella engenders. The potential for Legionella to become a health hazard to the point of being fatal to a large number of people is greatly enhanced by conventional water and air conditioning engineering methods used in re-circulating cooling towers, evaporative condensers, showers, fountains, artificial lakes, water storage and hot & cold water distribution systems. The risk is also present in health care systems such as dental chair units.
Dr Sanjeet Mishra, Technical Manager, ABC, said DNA-based testing for Legionella gives quicker and more accurate results than the conventional method, which takes 13-15 days compared to 48 hours for the DNA technique. He continued, "When you get a positive result at the end of 14 days, you realise that your system has been affected. However, for that period, you have exposed people staying or working in the premises to Legionella."
Both conventional and DNA based Legionella testing are recommended and performed in line with the American Public Health Association (APHA) method along with the ISO 11731 procedure. In the conventional method, the plate has to be incubated for at least seven days to produce a colony and under the right conditions too. Further, appropriate methods are utilised to try and ensure that except for Legionella, the growth of other organisms is prevented. At the end of 7-10 days, presumptive colonies are counted. The presumptive colonies are again subjected to confirmatory tests to determine whether it is a case of Legionella.
Dr Mishra explained that the principle behind the DNA based technique is simple: the DNA carries genetic information which is a characteristic of and specific to any organism, from a microbe to a human being and therefore, can be used as a signature for detection. Legionella has a unique DNA sequence which can be detected using conserved regions that can be targeted as markers or the target DNA.
The DNA-based PCR (Polymerase Chain Reaction) technique detection follows the same initial processing; the difference being that post-filtration, instead of putting the sample in the plate, DNA is directly extracted. When the extraction is done, the total DNA of all the organisms present in the sample is obtained. But the primers employed in the subsequent PCR are very specific in that it will amplify and detect only Legionella. "The PCR technique has revolutionised the concept of molecular diagnostic since as low as approximately 5-6 Legionella bacterial cells can be detected," said Dr Mishra.
Aided by suitable temperatures and relative humidity, the numerous residential and public buildings, district cooling plants, artificial water bodies, water features and irrigation systems can harbour and spread Legionella. Recognising the seriousness of the issue, Dubai Municipality has begun enforcing a three-month testing regime for Legionella. The Public Health & Safety Department of Dubai Municipality has also a strict regulation for testing Legionella in dental chairs.
However, while the authorities in Dubai accept the results obtained by DNA testing, customer acceptance in general has been a 'work in progress.' Existing guidelines are inclined towards the conventional technique because the remedial measures required to be taken depends on the count. But Dr Mishra feels that the bottom line should be zero-tolerance towards this potential health hazard. "If you have detected Legionella, it means that at some point of time, your system is infected. If the DNA test result is positive, you can start taking remedial measures from the 49th hour itself," he noted.
With regard to pricing, Dr Mishra claimed that for Legionella testing, the cost of DNA technique is at par with the conventional method. At present, ABC offers DNA testing for Legionella directly to customers in the hospitality industry and to Facility Management (FM) companies, District Cooling companies, government organisations, health care facilities etc and also to private home owners.
© H2O 2010
