Prevalence and Concentration of Non-tuberculous Mycobacteria in Cooling Towers by Means of Quantitative PCR: A Prospective Study
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There is an increasing level of interest in non-tuberculous mycobacteria (NTM) due to the increasing reported rates of diseases caused by them. Although it is well known that NTM are widely distributed in the environment it is necessary to identify its reservoirs to prevent possible infections. In this study, we aimed to investigate the occurrence and levels of NTM in cooling towers to provide evidences for considering these settings as possible sources of respiratory infections. In the current study, we detected and quantified the presence of NTM by means of a rapid method in water samples taken from 53 cooling towers of an urban area (Barcelona, Spain). A genus-specific quantitative PCR (Q-PCR) assay with a quantification limit (QL) of 500 cells l−1 was used. 56% (30) of samples were positive with a concentration range from 4.6 × 103 to 1.79 × 106 cells l−1. In some cases (9/30), samples were positive but with levels below the QL. The colonization rate confirmed that cooling towers could be considered as a potential reservoir for NTM. This study also evaluated Q-PCR as a useful method to detect and quantify NTM in samples coming from environmental sources.
We thank Dr. Enrico Tortoli (Regional Mycobacteria Reference Centre, Florence, Italy) and Dr. Núria Martin-Casabona (Vall d’Hebrón Hospital, Barcelona, Spain) for providing M. palustre and M. xenopi clinical isolates, respectively. We also thank Dr. Laura Villanueva (NIOZ Royal Netherlands Institute for Sea Research, The Netherlands) for critical revision of the manuscript. This work was supported by the Ministerio de Ciencia e Innovación with grant CTM2005-06457-C05-05/TECNO to JM, PI081062 grant to ET, SAF2006-05868 grant to EJ, and by 2009SGR-00108 grant to EJ and ML. ET and BA were supported by Ramon y Cajal and by FPI program (Ministerio de Ciencia e Innovación), respectively.
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