First Study in Qatar to Reveal High Legionella Count in Cooling Towers

Abstract

Legionella is an intracellular bacterium that can cause a severe communityacquired and nosocomial pneumonia, known as legionnaire disease (LD). The bacterium thrives in freshwater environments, including manmade water systems. Transmission from water to the human host is mediated by aerosols produced by devices such as cooling towers (CTs) and air conditioners. Hypothesis: CTs in Qatar contain significant counts of the organism, making it a potential waterborne pathogen to the local population. Objectives: Despite the abundance of central cooling systems in Qatar, there is no published report examining the presence of Legionella in them. The goal of this study is to investigate the presence of this organism in a number of CTs in Qatar. Methods: Ten CTs located at Qatar University were selected as a representative model for CTs in Qatar. A total of 94 water samples were collected from these CTs from November 2013 to July 2014. Suspected growth was recovered from water by filtration and concentration. DNA was extracted from the water concentrates and Legionella count was assessed by quantitative realtime PCR (qRTPCR). Results: Legionella species were found in 100% of the samples collected. The lowest count was .006 CFU/mL and the highest was 199.56 CFU/mL. As recommended by the CDC, the critical count of more than 10 CFU/mL represents a potential hazard. The count was found in 55.3 % of the samples. High counts were mainly seen in May and July in the old and new CT units, respectively. Conclusion: This is the first study of its kind in Qatar and it suggests that Legionella could be a potential health risk. Findings of the study call for the urgent need to investigate the Legionella count in potable water systems, develop a standard for count evaluation, and set up monitoring programs.