First study in Qatar to reveal high Legionella counts in cooling towers.

Legionella spp. is transmitted from water to humans by aerosol-generating devices, including cooling towers (CTs). There have not been published reports about Legionella in these systems in Qatar. Ten CTs in Qatar University were sampled on a monthly basis. Bacteria were recovered from 90 water samples by filtration and concentration. Legionella DNA copy number (CN) was assessed by quantitative RT-PCR. Legionella DNA was detected in 100% of the samples. The bacterial counts ranged from 0.006 to 199.56 CFU/mL, and critical counts were found in 51 (56.7 %) samples. Moreover, 7 (7.8%) samples showed a count of more than 100 CFU/mL. The highest counts were found in the months of May and June. These results suggest that this organism is found in high number in tested CTs, presenting a potential health risk to the local population.