Comparison and optimization of methods for isolation of Non-Tuberculous mycobacteria from surface water

Aim and Environment is the likely source of most Non-Tuberculous mycobacteria (NTM) involved in human infections, especially pulmonary, skin, and soft tissue infections. In order to measure the prevalence of NTM in different aquatic ecosystems, we tried to standardize the isolation methods used for surface water testing since many procedures have been described previously. Cultivation of mycobacteria requires long-term incubation in rich media and inactivation of rapidly growing microorganisms whose growth impedes observation of mycobacterial colonies. 38 samples were collected from surface waters in Tehran. Water sampling was carried out in a volume of 200-100 ml. water sample was transferred immediately to the laboratory and examined. Three methods (Cetylpyridinium chlori, Petroff, Tacquet-Tison) for the isolation of mycobacteria were compared by applying them in parallel to 38 samples of surface water. Each method was defined by a particular combination of decontamination method. The efficacy of each method was determined by calculating the positivity, negativity, and contamination rates, the mean numbers of mycobacterial colonies grown and number of different mycobacterial strains isolated. The last value was determined by subjecting the isolates to PCR. Decontamination with CPC appeared to be the best decontamination method, on the one hand, it significantly decreased the level of non-target microorganisms and, on the other hand, it was significantly less lethal for the NTM strains studied. Our goal was to measure the effects of various methods known to inhibit the growth of non-target microorganisms, while we also took into consideration the inhibitory effects of these methods on the growth of NTM. We propose that CPC procedure could be used for detection of NTM in aquatic samples.