Susceptibility of compound 48/80-sensitized Pseudomonas aeruginosa to the hydrophobic biocide triclosan

Abstract

Pseudomonas aeruginosa is intrinsically resistant to the hydrophobic biocide triclosan, and yet it can be sensitized to low concentrations by permeabilization of the outer membrane using compound 48/80. A selective plating assay revealed that compound 48/80-permeabilized YM64, a triclosan-recognizing efflux pump-deficient variant, was unable to initiate growth on a medium containing triclosan. Macrobroth dilution assay data revealed that treatment with compound 48/80 synergistically decreased minimal inhibitory concentrations of the hydrophobic antibacterial agents rifamycin SV and chloramphenicol for all cell envelope variant strains examined. A low concentration of triclosan exerted a transient bactericidal effect on permeabilized wild-type strain PAO1, after which exponential growth resumed within 4 h. Permeabilized strain YM64 was unable to overcome the inhibition; yet, both strains remained susceptible to chloramphenicol for as long as 6 h, thereby suggesting that the outer membrane remained permeable to nonpolar compounds. These data support the notion that the transitory nature of compound 48/80 sensitization to triclosan in P. aeruginosa does not involve obviation of the hydrophobic diffusion pathway through the outer membrane. The inability of strain YM64 to overcome the synergistic effect of compound 48/80 and triclosan strongly suggests that triclosan-recognizing efflux pumps are involved in maintaining viability in wild-type cells whose outer membranes are otherwise compromised.

Triclosan Resistance of Pseudomonas aeruginosa PAO1 Is Due to FabV, a Triclosan-Resistant Enoyl-Acyl Carrier Protein Reductase

“…It has been reported that inactivation of the MexAB-OprM multidrug efflux pump results in a decrease of P. aeruginosa PAO1 triclosan resistance from 1,000 g/ml to 16 g/ml (4, 5). However, other investigators have reported that inactivation of the MexABOprM efflux pump had either no effect (4, 10) or a minimal effect (10) on triclosan resistance unless the outer membrane was permeabilized by chemical agents (10). The differences among the MexAB-OprM reports may be due to the fact that the workers who reported the dramatic effects of MexAB-OprM inactivation (5) solubilized triclosan with 2-methoxyethanol, and this solvent may have permeabilized the outer membrane.…”

“…The supply sources were as follows: malonyl coenzyme A (malonyl-CoA), acetyl-CoA, fatty acids, triclosan, NADH, NADPH, and antibiotics were from Sigma; Takara Biotechnology Co. provided molecular biology reagents; Novagen provided pET vectors; American Radiolabeled Chemicals, Inc., provided sodium [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]acetate (specific activity, 50 mCi/mM); Invitrogen provided the Ni 2 -agarose column; and Bio-Rad provided the UNOsphere Q strong anion-exchange media and the Quick Start Bradford dye reagent. All other reagents were of the highest available quality.…”

Efflux-Mediated Drug Resistance in Bacteria

“…[271] As predicted from the synergy between the pumps and the OM barrier, an OM-permeabilizing polycationic compound 48/80[272] increased the susceptibility of P. aeruginosa to the hydrophobic biocide triclosan. [273]…”

Toxicogenomic Response of Rhodospirillum rubrum S1H to the Micropollutant Triclosan

“…The most frequently described Gram-negative mechanisms for defense against TCS are active efflux via pumps belonging to the resistance-nodulation-cell division (RND) family (13,43) and, to some extent, exclusion by making the cell envelope impermeable (11,18). Accordingly, the majority of the induced genes in R. rubrum were related to efflux systems.…”