Spiral Biotech, Inc.

Leon G Hunt

Samuel Schalkowsky

A method for measuring the combined bactericidal and bacteriostatic effects of an antimicrobial agent on the number of viable cells in a bacterial population exposed to an application-relevant concentration of the agent, with the rate of change of the number of viable cells as a function of different exposure intervals expressed on a per-drug-free division interval g.sub.0 (generation time) basis, so as to facilitate the assessment of projected therapeutic efficacy independent of the particular generation time used in the test environment. (2) A method for measuring the combined bactericidal and bacteriostatic effects of an antimicrobial agent on the acceleration of viable population change at a concentration corresponding to the Discrete Minimal Inhibitory Concentration (DMIC), when the size of the initial viable population remains essentially unchanged in the presence of the agent. (3) A method for measuring the bactericidal component of the effect of an antimicrobial agent from measurements of the initial viable population deposited on nutrient agar media and the number of visible colonies which formed from this deposit in the presence of a selected concentration of the antimicrobial agent. (4) A method for determining the value of the DMIC, and the rate of change of bactericidal activity with changing concentrations of the antimicrobial agent, by applying the method of (3) above at different concentrations of the antimicrobial agent; computing the probability of successful cell division from colony count data at the selected concentrations of the antimicrobial agent; evaluating the functional relationship between the probabilities of division and concentration of the agent; and obtaining from this function the value of the DMIC, the Minimum Cidal Concentration (MCC) where bactericidal activity begins and the rate of change of bactericidal activity with drug concentration.

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Arlington, VA, United States of America

Leon G Hunt