Microbial community of cooling towers in Quebec, Canada

Legionnaires' Disease is a severe pneumonia caused by the bacterium Legionella pneumophila. The disease is acquired through the inhalation of aerosols contaminated with the bacterium. Consequently, urban water systems are the main reservoir and vector for the spread of the disease. Cooling towers are by far the major source of large outbreaks, as they contain high amounts of water and produce vast quantities of aerosols. For this to happen, the cooling tower must present proper condition for L. pneumophila to colonize it and to grow to high level. The required conditions are poorly understood; However, several biological factors have been experimentally identified, such as the presence of free-living amoeba (FLA). Thus, we hypothesize that the microbial community of a cooling tower plays a crucial role in L. pneumophila outbreaks. A total of 18 cooling towers were sampled in Montreal, Quebec City, and in surrounding regions. These cooling towers were chosen as some of them had been known to harbour L. pneumophila in the past. One-litre water triplicates were sampled for each tower and the biomass was collected using filtration. DNA was extracted from the biomass and different chemical and physical parameters were measured on the filtered water. Bacterial contamination levels were measured using heterotrophic plate counts on R2A and nutrient agar. L. pneumophila levels were also measured using the iQ-Check Quanti L. pneumophila Kit. Finally, 16S rDNA amplicon sequencing was performed using the Illumina MiSeq platform.