Methods to determine fitness in bacteria.

Acquisition of antibiotic resistance may be associated with a physiological cost for the bacterium. Determination of growth rate and generation time is often used to measure fitness costs associated with antibiotic resistance. However, fitness costs may be small and difficult to quantify and multiple models are required. Available in vitro models that can be used to measure fitness include quantification of biofilm growth, survival in water, resistance to drying, and measurement of planktonic growth rates. The use of growth curve techniques to determine generation time is laborious, time-consuming, and can introduce sampling error. We have described the use of a semi-automated liquid culture system to estimate generation time in Burkholderia cepacia complex bacteria. We have also used the BacT/ALERT system to determine generation time and enumerate bacterial numbers in Mycobacterium tuberculosis. We describe methods for measuring biofilm growth and environmental survival in Burkholderia cepacia complex bacteria. These methods can be adapted for use with other organisms.