MATHEMATICAL-MODELING OF ADHESION OF BACTERIA TO HOST-CELL LINES

A mathematical model which describes adhesion of bacteria to host cell lines is presented. The model is flexible enough to account for the f ollowing situations: extracellular bacteria are either in exponential or in stationary phase. Adhesion is described as a reversible binding process in which the bacteria attach to or detach from specific recept ors uniformly distributed on the cell surface. In turn, attached bacte ria can either replicate or, conversely, they are restrained to remain in stationary phase. In the first case, however, we must consider the problem of whether the decrease of unoccupied receptors as adhesion p rogresses imposes a limit to the replicating capacity of the attached bacteria. The effect exerted by the multiplicity of infection (MOI), i .e. the ratio of the number of bacteria to the number of host cells, o n the process of adhesion is also contemplated by the model. This has revealed that experiments performed at the same values of MOI can show completely different levels of adhered bacteria, depending on the num ber of host cells in the assays. This finding demonstrates that the re port of the MOI values is insufficient to characterize comparative stu dies of bacterial adhesion since it could lead to a misunderstanding o f the corresponding data. Simplified models based on the steady-state approximation and in equilibrium analysis by means of a Lagmuir adsorp tion isotherm for the attached bacteria are also discussed. This allow s us to define the adhesion coefficient (beta) in a given bacterium-ce ll system so that, with the exception of those systems where these coe fficients cannot be defined, larger values of beta are related to a gr eater adhesion capacity. An overview of the procedures to perform quan titative adhesion data analysis is outlined. Finally, theoretical pred ictions are compared with experimental results from the literature. (C ) 1997 Society for Mathematical Biology.