Environmental Mycobacteria in Drinking Water Before and After Replacement of the Water Distribution Network

Environmental mycobacteria (M. chelonae (8), M.flavescens (6), M. gordonae (6), M. fortuitum (5), M. kansasii (4), M. phlei (2) and M. terrae (2)) were isolated from21.3% of drinking water samples before replacement of thedistribution network of Patras. After replacement of the networkonly 1.8% of the samples contained environmental mycobacteria(M. chelonae (2)). The identification of environmentalmycobacteria was performed by Restriction EnzymeAnalysis-Polymerase Chain Reaction. Our results showed no statistically significant correlationbetween the presence of mycobacteria and the bacteriologicalfecal indicators (p >0.05). Moreover, we determined thatconcentrations of free residual chlorine equal to or greaterthan 0.5 mg L super(-1) in the water supply network were needed toeliminate environmental mycobacteria.We conclude that the presence of a biofilm in the old Patrasdrinking water network significantly increased the number ofenvironmental mycobacteria in the drinking water. This problemwas resorted after the replacement of the network pipes.