Recovery of mycobacteria from heavily contaminated environmental matrices

Abstract

For epidemiology studies, a decontamination method using a solution containing 4.0% NaOH and 0.5% tetradecyltrimethylammonium bromide (TDAB) represents a rela-tively simple and universal procedure for processing heavily microbially contaminated matrices together with increase of mycobacteria yield and elimination of gross contami-nation. A contamination rate only averaging 7.3% (2.4% in Cluster S; 6.9%% in Cluster R and 12.6%% in Cluster E) was found in 787 examined environmental samples. Mycobac-teria were cultured from 28.5% of 274 soil and water sediments samples (Cluster S), 60.2% of 251 samples of raw and processed peat and other horticultural substrates (Cluster R), and 29.4% of 262 faecal samples along with other samples of animal origin (Cluster E). A total of 38 species of slow and rapidly growing mycobacteria were isolated. M. avium ssp. hominissuis, M. fortuitum, and M. malmoense were the species most often isolated. The pa-rameters for the quantitative detection of mycobacteria by PCR can be significantly re-fined by treating the sample suspension before DNA isolation with PMA (propidium monoazide) solution. This effectively eliminates DNA residue from both dead mycobac-terial cells and potentially interfering DNA segments present from other microbial flora. In terms of human exposure risk assessment, the potential exposure to live non‐tubercu-lous mycobacteria can be more accurately determined.