Assessing the Impact of Media on Antibiotic

Student Classification


Faculty Mentor

Dr. Misty Thomas



Document Type


Publication Date

Fall 2018


Background: The antibiotic crisis has come about due to the overuse and abuse of antibiotics in human and animal welfare. Due to this, it is predicted that soon, antibiotics that will no longer work to treat even common bacterial infections due to resistance; and the ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter species, and Mycobacterium tuberculosis) are at the forefront of the antibiotic resistance crisis. Soil bacteria have commonly been exploited in the past for their ability to produce antibiotics. Here we describe our work successfully isolating 32 antibiotic producing bacteria from the soil and assessing the effect that culture medium has on the production of their antimicrobial compounds. Hypothesis: We hypothesize that if the antibiotic-producing soil bacteria are placed on different types of media, then it will affect their production of antibiotics as different media offers different nutrients and therefore different stressors which may influence the necessity for antibiotic production. Methods: The ability of soil bacteria to produce antibiotics against ESKAPE pathogen safe relatives on different types of agar was tested. Bacteria were isolated via serial dilutions of soil samples from various locations. Each isolate was picked and patched onto swab plates of the ESKAPE relative on one of Luria-Bertani Agar (LBA), Reasoner’s 2A Agar (R2A), Trypticase Soy Agar (TSA) and Potato Dextrose Agar (PDA) and their ability to produce an antibiotic was assessed by characterization of zones of inhibitions. After analysis, 32 producing isolates were selected for their ability to produce an antimicrobial agent on one type of agar and subsequently plated on all 4 types of media to assess the changes in zones of inhibition on each media type. Results/Conclusions: 32 antibiotic producing soil isolates were identified and after screening these isolates and their antibiotic production on 4 different types of media, we found that media does have a significant impact on an isolates ability to produce an antibiotic. Significance: In understanding how culture medium affects antibiotic production by soil isolated bacteria, this allows us to create better screening methods for the detection and isolation of new antibiotics to fight the antibiotic crisis.

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