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Disparate efficacy of tobramycin on Ca(2+)-, Mg(2+)-, and HEPES-treated Pseudomonas aeruginosa biofilms.
Hoyle, B D; Wong, C K; Costerton, J W.
Affiliation
  • Hoyle BD; Department of Biological Sciences, University of Calgary, Alta., Canada.
Can J Microbiol ; 38(11): 1214-8, 1992 Nov.
Article in En | MEDLINE | ID: mdl-1477794
Mucoid exopolysaccharide (MEP) obtained from Pseudomonas aeruginosa 579 was suspended in 10 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) pH 7.2 containing 0.1-10.0 mM of CaCl2.2H2O or MgCl2.4H2O. MEP treated with HEPES or < 5.0 mM of the Ca2+ or Mg2+ salts remained soluble and bound tobramycin in an equilibrium dialysis bioassay. MEP treated with 5.0 or 10.0 mM of the Ca2+ or Mg2+ salts did not bind tobramycin. Five and 10 mM Ca(2+)-treated MEP precipitated but Mg(2+)-treated MEP did not. Pseudomonas aeruginosa 579 biofilms formed using a defined growth medium having < 1 mM Ca2+ or Mg2+ were treated for 1 h with 10 mM HEPES +/- 5.0 mM CaCl2.2H2O or MgCl2.4H2O, prior to an 8-h exposure to HEPES, or the defined growth medium, +/- 125 micrograms/mL of tobramycin. The tobramycin kill kinetics for the HEPES-, Mg(2+)-, and Ca(2+)-treated biofilms were similar and gradual from T = 0-6 h. The viability of the HEPES- and Mg(2+)-treated populations declined sharply (from 6 to 8 h). Bacteria dispersed from the MEP in control biofilms at 0 and 8 h did not grow in the presence of 7.81 micrograms/mL of tobramycin. Thus, binding of tobramycin of P. aeruginosa 579 MEP may not be as influential to the impediment of tobramycin diffusion as is the steric hindrance imposed by the Ca2+ condensation of the polymer.
Subject(s)
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Collection: 01-internacional Database: MEDLINE Main subject: Pseudomonas aeruginosa / Tobramycin Language: En Journal: Can J Microbiol Year: 1992 Document type: Article Affiliation country: Country of publication:
Search on Google
Collection: 01-internacional Database: MEDLINE Main subject: Pseudomonas aeruginosa / Tobramycin Language: En Journal: Can J Microbiol Year: 1992 Document type: Article Affiliation country: Country of publication: