Resistance of Pseudomonas aeruginosa to isothiazolone.
This investigation was to determine whether Pseudomonas aeruginosa could acquire resistance to the bactericide isothiazolone, and what the nature of such a resistance mechanism would be. The Pseudomonas was cultured in nutrient-limited broth in the presence of sub-inhibitory concentrations of isothiazolone (a mixture of 1.15% 5-chloro-N-methylisothiazolone (CMIT) and 0.35% N-methylisothiazolone (MIT)). Three cultures tested in parallel adapted gradually during exposure for 15 d from an initial minimum inhibitory concentration (MIC) of 300 microliters l-1 to 607 microliters l-1. The three parallel cultures adapted at similar rates, so the adaptation was not ascribed to mutation but to a specific mechanism. Resistant cells did not produce any extracellular isothiazolone-quenching compounds nor undergo detectable alterations in their lipopolysaccharide layer. In wild cells, a 35 kDa outer membrane protein (protein T) was detectable, whereas resistant cells lacked this protein. Production of protein T was suppressed within 24 h of exposure to isothiazolone. It was still suppressed after 72 h of growth in isothiazolone-free medium. It is proposed that Ps. aeruginosa acquires resistance to isothiazolone by a process of adaptation where the outer membrane protein T is suppressed.
Brözel
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Department of Microbiology and Plant Pathology, University of Pretoria, South Africa.
Cloete
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TE
D000596:Amino Acids / Q000032:analysis; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis; D004352:Drug Resistance, Microbial; D008070:Lipopolysaccharides / Q000032:analysis; D008826:Microbial Sensitivity Tests; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000187:drug effects*; D013844:Thiazoles / Q000494:pharmacology*
D000596:Amino Acids; D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D008070:Lipopolysaccharides; D013844:Thiazoles; C011506:2-methyl-4-isothiazolin-3-one; C011421:5-chloro-2-methyl-4-isothiazolin-3-one