Disparate properties of Burkholderia multivorans and Pseudomonas aeruginosa regarding outer membrane chemical permeabilization to the hydrophobic substances novobiocin and triclosan.

Burkholderia multivorans causes opportunistic pulmonary infections and is intrinsically resistant to many antibacterial compounds including the hydrophobic biocide triclosan. Chemical permeabilization of the Pseudomonas aeruginosa outer membrane affects sensitization to hydrophobic substances. The purpose of the present study was to determine if B. multivorans is similarly susceptive suggesting that outer membrane impermeability properties underlie triclosan resistance. Antibiograms and conventional macrobroth dilution bioassays were employed to establish baseline susceptibility levels to hydrophobic antibacterial compounds. Outer membrane permeabilizers compound 48/80, polymyxin B, polymyxin B-nonapeptide, and ethylenediaminetetraacetic acid were used in attempts to sensitize disparate B. multivorans isolates to the hydrophobic agents novobiocin and triclosan, and to potentiate partitioning of the hydrophobic fluorescent probe 1-N-phenylnapthylamine (NPN). The lipophilic agent resistance profiles for all B. multivorans strains were essentially the same as that of P. aeruginosa except that they were resistant to polymyxin B. Moreover, they resisted sensitization to hydrophobic compounds and remained inaccessible to NPN when treated with outer membrane permeabilizers. These data support the notion that while both phylogenetically-related organisms exhibit general intrinsic resistance properties to hydrophobic substances, the outer membrane of B. multivorans either resists permeabilization by chemical modification or sensitization is mitigated by a supplemental mechanism not present in P. aeruginosa.

Cell surface physiology and outer cell envelope impermeability for hydrophobic substances in Burkholderia multivorans.

PURPOSE: The purpose of the present study was to obtain a better understanding of the relationship between cell surface physiology and outer cellular envelope permeability for hydrophobic substances in mucoid and non-mucoid B. multivorans strains, as well as in two capsule-deficient derivatives of a mucoid parental strain. METHODOLOGY: Cell surface hydrophobicity properties were determined using the hydrocarbon adherence method, while outer cell envelope accessibility and permeability for non-polar compounds were measured using hydrophobic antimicrobial agent susceptibility and fluorescent probe assays. Extracellular polysaccharide (EPS) production was assessed by cultivating strains of disparate origin on yeast extract agar (YEA) containing different sugars, while the resultant colonial and cellular morphological parameters were assessed macro- and microscopically, respectively.Results/Key findings. The cell surfaces of all the strains were hydrophilic, impermeable to mechanistically disparate hydrophobic antibacterial agents and inaccessible to the hydrophobic probe N-phenyl-1-napthylamine, regardless of EPS phenotype. Supplementation of basal YEA with eight different sugars enhanced macroscopic EPS expression for all but one non-mucoid strain, with mannose potentiating the greatest effect. Despite acquisition of the mucoid phenotype, non-mucoid strains remained non-capsulated and capsulation of a hyper-mucoid strain and its two non-mucoid derivative strains was unaffected, as judged by microscopic observation. CONCLUSION: These data support the conclusion that EPS expression and the consistent mucoid phenotype are not necessarily associated with the ability of the outer cell surface to associate with non-polar substances or cellular capsulation.

Cell envelope phospholipid composition of Burkholderia multivorans.

Burkholderia multivorans causes opportunistic pulmonary infections in cystic fibrosis and immunocompromised patients. The purpose of the present study was to determine the nature of the phospholipids and their fatty acid constituents comprising the cell envelope membranes of strains isolated from three disparate sources. A conventional method for obtaining the readily extractable lipids fraction from bacteria was employed to obtain membrane lipids for thin-layer chromatographic and gas chromatography-mass spectrophotometric analyses. Major fatty acid components of the B. multivorans readily extractable lipid fractions included C(16:0) (palmitic acid), C(16:1) (palmitoleic acid), and C(18:1) (oleic acid), while C(14:0) (myristic acid), ΔC(17:0) (methylene hexadecanoic acid), C(18:0) (stearic acid), and ΔC(19:0) (methylene octadecanoic acid) were present in lesser amounts. Fatty acid composition differed quantitatively among strains with regard to C(16:0), C(16:1), ΔC(17:0), C(18:1), and ΔC(19:0) with the unsaturated:saturated fatty acid ratios being significantly less in a cystic fibrosis type strain than either environmental or chronic granulomatous disease strains. Phospholipids identified in all B. multivorans strains included lyso-phosphatidylethanolamine, phosphatidylglycerol, phosphatidylethanolamine, and diphosphatidylglycerol in similar ratios. These data support the conclusion that the cell envelope phospholipid profiles of disparate B. multivorans strains are similar, while their respective fatty acyl substituent profiles differ quantitatively under identical cultivation conditions.