Faster Legionella testing on horizon

To date, however, a lack of consensus on how to interpret such results in relation to those from culture has been a stumbling block, although, as Susan Pearson, a freelance journalist and public relations consultant specialising in medicine and the environment, reports, the positive results of a recent multi-centre European study mean this could soon all change.
 Around 300-400 cases of Legionnaires’ disease are reported every year in England and Wales, and, while the incidence is low in hospitals, those affected will be the most susceptible – the immuno-compromised, ICU patients, transplant and oncology patients, diabetics, smokers, and alcoholics – and the most likely to die. While the mortality rate for the general population is around 13%, the nosocomial rate has reached 32%. Legionnaires’ disease is the severest form of infection caused by Legionella bacteria, opportunistic waterborne pathogens which occur naturally in the environment. Of the 50-plus species, only 20 appear to be associated with disease in humans, with Legionella pneumophila by far and away the most significant. Victims are infected by inhaling organisms suspended in air from an aerosol, or sometimes by aspiration, particularly in the case of hospital patients. Although less than 5% of exposed individuals will develop Legionnaires’ disease, up to 95% may contract a milder form of legionellosis known as Pontiac Fever, a short, influenza-like illness that does not require treatment. However, some exposed individuals will remain completely symptomless.

Dormant at low temperatures

Dormant at low temperatures, Legionella multiplies to large numbers in water between temperatures of 20°C and 45°C, and cannot survive at temperatures above 50°C. Other risk factors for outbreaks are water stagnation, for example in pipework “dead legs”, leading to build-up of biofilm which harbours pathogenic bacteria, and lack of appropriate biocide concentrations. Although 27% of Legionnaires’ disease outbreaks are associated with cooling towers, hot and cold water systems are also major culprits, with spa pools the third most significant source. In new buildings, warmer weather and energy conservation requirements are also making cold water systems more vulnerable to microbial contamination. Heat is now better retained in buildings, and is transferred to the cooler parts of the building – normally the cold water system. Even well-insulated pipes may be inappropriately “warmed” by hot pipes running alongside cold pipes in service ducts, or above ceiling-mounted radiant heat panels. In the UK, there is a legal requirement to follow the “L8” guidelines1 to prevent Legionnaires’ disease, which includes sampling for Legionella species to monitor the effectiveness of control measures against the organism.