ABSTRACT
Sometimes it is important to know exactly how many cells are present in a liquid culture or adherent monolayer. Sometimes only the number of cells relative to a control culture or an earlier time point is what is required. The usual method for quantifying bacterial concentration in a solution is by using ultraviolet-visible absorbance spectroscopy to measure the absorbance of the solution at a particular wavelength, usually 600 nm. Bacteria may be counted on a hemocytometer, which is a gridded slide containing a well of calibrated volume specifically designed for counting cells. A method of obtaining the count of viable bacteria in a culture is by plating and counting colonies, a method called plate count. The addition of antibiotic agents can affect the growth curve in multiple nonlinear ways. The minimum inhibitory concentration (MIC) is defined as the concentration of an agent that kills 99.9" of a specific microorganism in a specific growth medium within a certain time point.
