Chloromethyl-methylisothiazolone (CMIT/MIT) is a broad spectrum biocide which has been used
successfully for microbial control and preventing biofouling in industrial water treatment. This paper
presents a review of the various reports over the past 20 years on the efficacy of CMIT/MIT biocide
versus Legionella bacteria and the protozoa associated with their growth. These studies included a wide
range of conditions, including single organisms in cooling water and complex model systems with
bacteria, biofilms, and protozoa. Overall, low levels of CMIT/MIT (1-10 ppm active) provided
significant reduction in viable counts of various strains and species of Legionella bacteria in planktonic
and biofilm studies and also against the amoebae and ciliated protozoa associated with their growth.