Mathematical modelling of growth of Escherichia coli at subinhibitory levels of chloramphenicol or tetracyclines.

A mathematical model is suggested to describe the subinhibitory effects of chloramphenicol upon growth of Escherichia coli. It represents a generalization of Monod's equation. Our model was constructed entirely on the basis of biochemical factors, such as the reversibility of the interaction between the drug and its ribosomal target or intracellular uptake. The subinhibitory effects of chloramphenicol were satisfactorily described by this law within the range of 0.4-2.4 micrograms/ml. After simplifying the equation, this model was extrapolated to provide an accurate description of the mode of action of other bacteriostatic antibiotics which also inhibit the 50-S ribosomal subunit (tetracycline and doxycycline). The expanded model seems to accurately typify the effect of these antibiotics, whereas bactericidal aminoglycosides follow a completely different growth law.