Antimicrobial resistance that develops in bacteria is a highly studied aspect of microbiology due to the concerns that it poses for public health. Antibiotics remain our primary care option when dealing with bacterial infections. The concept of tolerance of bacteria to disinfectants is similar and it also poses a significant health risk. Since use of disinfectants for sanitation is a primary manner in which we are able to prevent potential infections from occurring in the first place, it can be a helpful means to preventing development of antimicrobial resistance. However, what has not been explored to the same extent is whether an increase in tolerance to disinfectants due to their misuse can also influence tolerance to antimicrobials as well. Antimicrobial tolerance is different from antimicrobial resistance because the bacteria are still negatively affected when they are only able to tolerate an antimicrobial. The purpose of this study was to attempt to determine if there is an effect on antimicrobial tolerance, specifically an increase in antimicrobial tolerance, in bacteria when they are exposed to sub-lethal concentrations of a disinfectant. Sub-lethal disinfectant concentrations were used as an artificial selection pressure to attempt to force the bacteria to undergo adaptive mutation. If the adaptive response leading to an increased tolerance to the disinfectant is an example of cross-resistance that is linked with antimicrobial resistance, then an increase in antimicrobial tolerance was hypothesized to occur as well. There was no statistically significant effect observed on the tolerance levels to the antimicrobials used for the bacteria that had been exposed to the sub-lethal concentration of disinfectant. However, there were some trends observed that indicate that there is a difference in antimicrobial tolerance levels for tetracycline for both methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) that were promising. These trends suggest that there is an effect on the bacterial response to tetracycline following disinfectant treatment. This could present a significant public health dilemma as antimicrobial resistance is already a major problem. With these results indicating another potential method of adaption and development of antimicrobial resistance, it is concerning and merits future investigation for verification.


Timothy Secott

Committee Member

Allison Land

Committee Member

Yongtao Zhu

Date of Degree




Document Type



Master of Science (MS)

Program of Study



Biological Sciences


Science, Engineering and Technology

Included in

Bacteriology Commons



Rights Statement

In Copyright