Assessing the effectiveness of low-pressure ultraviolet light for inactivating Mycobacterium avium complex (MAC)...

To assess low-pressure ultraviolet light (LP-UV) inactivation kinetics of Mycobacterium avium complex (MAC) strains in a water matrix using collimated beam apparatus.

Strains of M. avium (n = 3) and Mycobacterium intracellulare (n = 2) were exposed to LP-UV, and log(10) inactivation and inactivation kinetics were evaluated. All strains exhibited greater than 4 log(10) inactivation at fluences of less than 20 mJ cm(-2). Repair potential was evaluated using one M. avium strain. Light repair was evaluated by simultaneous exposure using visible and LP-UV irradiation. Dark repair was evaluated by incubating UV-exposed organisms in the dark for 4 h. The isolate did not exhibit light or dark repair activity.

Results indicate that MAC organisms are readily inactivated at UV fluences typically used in drinking water treatment. Differences in activation kinetics were small but statistically significant between some tested isolates.

Results provide LP-UV inactivation kinetics for isolates from the relatively resistant MAC. Although UV inactivation of Mycobacterium species have been reported previously, data collected in this effort are comparable with recent UV inactivation research efforts performed in a similar manner. Data were assessed using a rigorous statistical approach and were useful towards modelling efforts.