Reduced glutaraldehyde susceptibility in Mycobacterium chelonae associatedwith altered cell wall polysaccharides

Glutaraldehyde-resistant Mycobacterium chelonae have been isolated from end oscope washer disinfectors and endoscope rinse water. The mechanism of glut araldehyde resistance is not well understood. Two spontaneous, glutaraldehy de-resistant mutants of the sensitive type strain, NCTC 946, were investiga ted. The colony morphology of the two mutants differed from that of the the type strain: colonies of the former were dry and waxy whereas those of the latter were smooth and shiny. Increased resistance to glutaraldehyde of th e mutants was matched by small increases in the MICs of rifampicin and etha mbutol but not isoniazid. Both mutants showed increased surface hydrophobic ity. No changes were identified in the extractable fatty acids or the mycol ic acid components of the cell wall but a reduction in each of the resistan t strains in the arabinogalactan/arabinomannan portion of the cell wall was detected.