The occurrence of Mycobacterium kansasii in tapwater.

M. kansasii was demonstrated in tapwater in the city of Rotterdam. Out of 78 taps examined 6 times during 1 year, 49 per cent yielded M. kansasii at least once. Examination of over 100 samples of the mains water supply yielded only 1 positive sample. The data suggest colonization of the water systems within buildings by M. kansasii in particular places. Phage typing demonstrated human and tapwater isolates to belong to the same phage types.