title: A mechanistical model for the uptake of sulfonamides by bacteria.
abstract: The uptake of sulfonamides into bacterial cells was simulated by a dynamic model to estimate bioavailability and steady-state accumulation of sulfonamides in the cells. Uptake of sulfonamides is modeled as diffusion-like transport of the neutral molecule and the ionic species. Speciation outside and inside the cell depends on the extra- and intracellular pH and the pK(a)-value of the antibiotic active SO(2)NH moiety. The ratio between intra- and extracellular sulfonamide concentration is used as a measure for potential sulfonamide accumulation in bacterial cells. Simulated ratios are in good agreement with experimental data for various sulfonamides with pK(a2) values ranging from 5.0 up to 11.8. Sensitivity analyses indicate that intracellular sulfonamide concentration depend significantly on the degree of ionization in the cytoplasm and the surrounding medium. No accumulation in the cell occurs, if the external pH exceeds the intracellular pH. For sulfonamides with large pK(a)-values the internal activity equals the activity in the extracellular solution. Highest accumulation is reached if the pH gradient from inside to outside the cell is large, which depends on the bacterial pH-regulation mechanisms. The pH-dependent intracellular accumulation of various sulfonamides correlates well with their observed antibiotic effect on selected bacteria.
authors.affiliation: Institute of Environmental Systems Research, University of Osnabrück, Barbarastr. 12, 49076 Osnabrück, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Zarfl
authors.forename: Michael
authors.initials: M
authors.lastname: Matthies
authors.forename: Jörg
authors.initials: J
authors.lastname: Klasmeier
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000494:pharmacology; D001419:Bacteria / Q000378:metabolism*; D001692:Biological Transport; D002463:Cell Membrane Permeability; D004058:Diffusion; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D013449:Sulfonamides / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D013449:Sulfonamides