Mycobactericidal activity of selected disinfectants using a quantitative suspension test

In this study, a quantitative suspension test carried out under both clean and dirty conditions was used to assess the activity of various instrument and environmental disinfectants against the type strain NCTC 946 and an end oscope washer disinfector isolate of Mycobacterium chelonae, Mycobacterium fortuitum NCTC 10394, Mycobacterium tuberculosis H37 Rv NCTC 7416 and a cli nical isolate of Mycobacterium avium-intracellulare (MAI). The disinfectant s tested were; a chlorine releasing agent, sodium dichloroisocyanurate (NaD CC) at 1000 ppm and 10 000 pm av Cl; chlorine dioxide at 1100 ppm av ClO2 ( Tristel, MediChem International Limited); 70% industrial methylated spirits (IMS); 2% alkaline glutaraldehyde (Asep, Galan); 10% succinedialdehyde and formaldehyde mixture (Gigasept, Schulke & Mayr); 0.35% peracetic acid (NuC idex, Johnson & Johnson); and a peroxygen compound at 1% and 3% (Virkon, An tec International). Results showed that the clinical isolate of MAI was muc h more resistant than M. tuberculosis to all the disinfectants, while the t ype strains of M. chelonae and M. fortuitum were far more sensitive. The wa sher disinfector isolate of M. chelonae was extremely resistant to 2% alkal ine activated glutaraldehyde and appeared to be slightly more resistant tha n the type strain to Nu-Cidex(R), Gigasept(R), Virkon(R) and the lower conc entration of NaDCC. This study has shown peracetic acid (Nu-Cidex), chlorin e dioxide (Tristel(R)), alcohol (IMS) and high concentrations of a chlorine releasing agent (NaDCC) are rapidly mycobactericidal. Glutaraldehyde, alth ough effective, is a slow mycobactericide. Gigasept and Virkon are poor myc obactericidal agents and are not therefore recommended for instruments or s pillage if mycobacteria are likely to be present.