Abstract
Misuse of antibiotics, coupled with a lack of new antibiotics being discovered, has threatened our ability to treat bacterial infections. Confounding our ability to effectively combat antibiotic resistance is the myriad of ways in which bacteria can resist antibiotic treatment. One mechanism is the inoculum effect, a phenomenon in which the inhibitory concentration of an antibiotic increases with initial cell density. Previously acquired data has indicated a mutation exclusive mechanism by which resistance arises. However, it is currently unknown as to whether or not the generation of antibiotic resistant bacteria due to spontaneous mutation plays a role in the inoculum effect. The purpose of this study was to examine the role, if any, that spontaneous mutation plays in resistance due to the inoculum effect. To assess this, we grew Escherichia coli in the presence of increasing concentrations of the antibiotic kanamycin. Here, we observed the presence of spontaneous mutation that led to antibiotic resistant bacteria. Furthermore, by perturbing the cellular network responsible for the inoculum effect, we were able to alter the mutation frequency. To examine if spontaneous mutations could also arise in a dynamic setting, we built a microfluidic flow system that allowed antibiotics to be delivered at defined intervals to a population. We observed that under these dynamic conditions, spontaneous mutants could still arise but not completely account for the total bacterial growth observed. Overall, our results indicate that the inoculum effect may provide an extended window in which antibiotic resistance due to genetic mutations can arise.
Faculty Sponsors
Louis Nemzer, Ph.D., Robert Smith, Ph.D.
Project Type
Event
Location
Alvin Sherman Library
Start Date
4-10-2015 1:00 PM
End Date
4-10-2015 5:30 PM
Invegstigating the Causes of Antibiotic Resistance in a Periodic Environment
Alvin Sherman Library
Misuse of antibiotics, coupled with a lack of new antibiotics being discovered, has threatened our ability to treat bacterial infections. Confounding our ability to effectively combat antibiotic resistance is the myriad of ways in which bacteria can resist antibiotic treatment. One mechanism is the inoculum effect, a phenomenon in which the inhibitory concentration of an antibiotic increases with initial cell density. Previously acquired data has indicated a mutation exclusive mechanism by which resistance arises. However, it is currently unknown as to whether or not the generation of antibiotic resistant bacteria due to spontaneous mutation plays a role in the inoculum effect. The purpose of this study was to examine the role, if any, that spontaneous mutation plays in resistance due to the inoculum effect. To assess this, we grew Escherichia coli in the presence of increasing concentrations of the antibiotic kanamycin. Here, we observed the presence of spontaneous mutation that led to antibiotic resistant bacteria. Furthermore, by perturbing the cellular network responsible for the inoculum effect, we were able to alter the mutation frequency. To examine if spontaneous mutations could also arise in a dynamic setting, we built a microfluidic flow system that allowed antibiotics to be delivered at defined intervals to a population. We observed that under these dynamic conditions, spontaneous mutants could still arise but not completely account for the total bacterial growth observed. Overall, our results indicate that the inoculum effect may provide an extended window in which antibiotic resistance due to genetic mutations can arise.
