Robustness of colony biofilm antibiotic tolerance

The conclusions of Zuroff et al. (2010) is given below.

“Biofilm antibiotic tolerance can vary in unpredictable manners based on modest changes in culturing conditions. Common antimicrobial testing methods, which only consider a single culturing condition, are not desirable since slight culturing variations can lead to very different outcomes. The presented data suggest it is essential to test antimicrobial strategies over a range of culturing perturbations relevant to the targeted application. In addition, the highly dynamic antibiotic tolerance responses observed here may explain why some current antimicrobial strategies occasionally fail.”

The authors found that in vitro colony biofilm antibiotic tolerance can vary considerably depending on perturbations in nutrient availability, temperature, age of biofilm etc. Earlier, other researchers have used only a single culturing condition (i.e. incubated bacterial cultures with a single dose and concentration of antibiotic, for a specified time of incubation using a specific inoculum size. The effect of nutrients and temperature has not been considered) in their experiments and extrapolated those results to derive at certain conclusions. However, the conclusions derived from single culturing conditions may not be reliable. In fact, this is one of the points stressed in my book and the previous blogposts as far as demonstration of persisters and their phenotypic shift is concerned. This highly dynamic antibiotic tolerance response may also explain why it is taking long time for antibiofilm agents to be available in the market (Romero and Kolter 2011).

Zuroff et al. (2010). Robustness analysis of culturing perturbations on Escherichia coli biofilm beta-lactam and aminoglycoside antibiotic tolerance. BMC Microbiology 10:185  

Romero, D. and Kolter, R. (2011). Will biofilm disassembly agents make it to the market? Trends in Microbiology 19(7): 304-306.