Effect of outer membrane permeabilisation on intrinsic resistance to low triclosan levels in Pseudomonas aeruginosa

Influence of methylation on the antibacterial properties of triclosan in Pasteurella multocida and Pseudomonas aeruginosa variant strains

“…Triclosan has also been incorporated into products such as gloves (Mixon, 1999) the presence of triclosan in lakes and a river in Switzerland and reported that triclosan and its methyl derivative were only found in the lakes studied which had anthropogenic sources, while both were absent in a remote mountain lake. This finding supports the notion that environmental triclosan accumulation is due to frequent incorporation into products for human use and that The triclosan minimal inhibitory concentration for P. aeruginosa far exceeds its solubility in aqueous media (Champlin et al, 2005). It was therefore necessary to determine the effect of methylation on triclosan efficacy using susceptible organisms such as P. multocida for bioassay purposes.…”

“…Triclosan is not soluble in aqueous media at concentrations greater than 32 µg/ml, a value far less than its minimal inhibitory concentration for P. aeruginosa (Champlin et al, 2005;. Therefore, the effect of triclosan and methyl triclosan on the ability to initiate growth was determined using a modification of a standardized disk agar diffusion bioassay (Hart and Champlin, 1988 …”

“…Previous work in this laboratory has shown the opportunistic pathogen Pasteurella multocida to be highly susceptible to triclosan despite its ultrastructurally typical gram-negative cell envelope (Champlin et al, 2005). Subsequent research determined such growth inhibition to be either bacteriostatic or bactericidal in a dose-dependent manner.…”

“…Enhanced uptake of the hydrophobic probe 1-N-phenylnaphthylamine relative to the refractory control organisms P. aeruginosa and Escherichia coli suggested the presence of regions of surface-exposed phospholipid bilayer in the P. multocida outer membrane. It was concluded that the extreme susceptibility of P. multocida to triclosan (Champlin et al, 2005) as well as other nonpolar antimicrobial agents (Hart and Champlin, 1988) is due to the general inability of the outer membrane to exclude hydrophobic molecules. Low triclosan concentrations which inhibited growth of untreated P. multocida cultures were only effective for P. aeruginosa when rendered susceptible using outer membrane-permeabilizing concentrations of polymyxin Bnonapeptide, compound 48/80, or ethylenediaminetetraacetate (Champlin et al, 2005).…”

“…It was therefore necessary to determine the effect of methylation on triclosan efficacy using susceptible organisms such as P. multocida for bioassay purposes. Wild-type P. aeruginosa K799, mutant P. aeruginosa Z61 (a genetic variant possessing a permeable outer membrane phenotype) (Nikaido and Vaara, 1985;Zimmermann, 1979), and outer membrane permeabilized wild-type P. aeruginosa PA01 were also examined in order to assess the possible involvement of outer membrane exclusion (Champlin et al, 2005) …”