Non Tuberculosis Mycobacterium, E. coli and E. faecalis from Biofilm in Drinking Water Distribution Systems from Selected Sites of Addis Ababa

The decline in microbial quality of drinking water may be attributed to many factors among which the presence of biofilm within the distribution system is the major cause of contamination. Drinking water distribution systems provide an oligotrophic environment, for post-treatment recovery and regrowth of microorganisms including the opportunistic Nontuberculosis Mycobacterium (NTM).

The aim was to look for opportunistic non tuberculosis mycobacterium and indicator organisms of fecal contamination from biofilm in drinking water distribution pipeline from selected sites of Addis Ababa.

A total of 40 biofilm samples were collected from two sub-cities of Addis Ababa. Biofilm samples were taken from the inner surfaces of the get valve and water meter. For the detection of E. coli and E. faecalis, diluted biofilm samples were filtered, then it was incubated on respective culture media. For non-tuberculosis mycobacterium, the homogenized biofilm sediment was processed using the standard SD bio line method, whereby, The processed sediment was inoculated to appropriate solid and liquid culture media. The DNA extraction was conducted by chemical lysis followed by PCR amplification, from the grown colonies on LJ media (Löwenstein–Jensen). The identification of Mycobacterium species was performed by reverse hybridization using a membrane strip and an enzymatic color reaction.

From the total biofilm samples, 14 out of 40 (35%) were positive for mycobacteria species. M. gordonea was the most prevalent specie of Mycobacterium, whereby 8/14 (57.1%) of the isolates were from this species followed by M. fortuitum 1/14 (7.14%). About (35.7%) 5/14 of the genus Mycobaterium were unidentified species. Indicator organisms of fecal contamination (E. coli and E. faecalis) were found in 3/40(7.5%) and 6/40(15%) respectively. There was no statistically significant association between nontuberculosis mycobacterium and the indicator organisms at p value of 0.01.

The study has highlighted that the occurrence of NTM in drinking water distribution in a significant proportion. M. gordonae was found to be the most dominant species of nontuberculosis mycobacterium found in the distribution line biofilm samples.