Emilee Kay Zoog



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Antibiotic resistance in bacterial pathogens has been a growing concern in recent years as infections that were once easily treated are becoming bigger threats. In agriculture and healthcare, the importance of antibiotic stewardship has been emphasized in an effort to decrease the overuse of antibiotics. Development of novel antibiotics and improvement in current antibiotic testing protocols are two additional avenues being pursued to solve the issue. In this study, I tested the effects of hypoxia on the antibiotic susceptibility in two human pathogens, Listeria monocytogenes and five different strains of Staphylococcus aureus (USA 300, Romero, COL, Newman, and SH1000), using a standard disc diffusion assay. However, in addition to the standard aerobic incubation, anaerobic incubation was also performed to understand whether hypoxia affects antibiotic susceptibility in these pathogens. My results showed that susceptibility to rifampin, ciprofloxacin, chloramphenicol, and tetracycline increased in an anaerobic environment while susceptibility to erythromycin and bacitracin decreased in an anaerobic environment. Listeria was resistant to streptomycin and penicillin in both environments. Similarly, all five strains of S. aureus exhibited changes in antibiotic susceptibility during hypoxia. For example, the methicillin-resistant S. aureus strain USA300 became more susceptible to rifampin, ciprofloxacin, and penicillin in an anaerobic environment. These results suggest that oxygen levels play a key role in bacteria susceptibility to antibiotics. Therefore, we need to consider the effectiveness of antibiotics under relevant environmental conditions to help antibiotic usage become more efficient.

Publication Date


Project Designation

Independent Research

Primary Advisor

Yvonne Y. Sun

Primary Advisor's Department



Stander Symposium project

The role of oxygen in antibiotic resistance in Listeria monocytogenes and Staphylococcus aureus