PENETRATION OF HOST-CELL LINES BY BACTERIA - CHARACTERISTICS OF THE PROCESS OF INTRACELLULAR BACTERIAL-INFECTION

A model which describes the characteristics of the penetration of the cells by bacteria is presented. Since the process of invasion is prece ded necessarily by the step in which the bacteria adhere to the cells, the proposed model is based on the expressions previously derived for the process of adhesion, which allow us to determine the number of at tached bacteria under different conditions. Thus, the model considers that invasion occurs irreversibly from attached bacteria to specific r eceptors located on the cell surface with a rate coefficient = k(i) so that the invasive capacity in a given bacterium-host cell system is m ainly determined by the value of this coefficient. Once internalized, the bacteria can follow three different time courses, namely: 1) intra cellular growth is hindered so that the bacteria remain in stationary phase, 2) there is a lag phase during which the bacteria stay in stati onary phase before they are able to grow exponentially with a rate coe fficient = k(c), and 3) the bacteria exhibit a growth exponential phas e as they enter the cells. In turn, the time course followed by extrac ellular bacteria also has a decisive influence on the process of invas ion and, in this regard, unbound bacteria are considered either in sta tionary or in exponential phase. Expressions for these different situa tions have been derived, and from them, procedures to determine the le vels of bacterial infection and for quantitative invasive data analysi s are presented. (C) 1997 Society for Mathematical Biology.