Development and Application of Bioassays to Quantify the Potency of β -Lactam Antibiotics
Mark Trujillo, Engie Ho, Nada Elshaer, Caitlin Davis
Department of Chemistry & Biochemistry
Faculty Supervisor: George Gassner
β-lactam antibiotics represent one of the most important first line treatments for life threatening gram-positive bacterial infections. Current industrial approaches to synthesis are reliant on toxic reagents and organic solvent systems. To improve accessibility and minimize environmental impact, our lab is developing a green-chemical cell-free biocatalytic pathway for the production of semisynthetic penicillins. In this poster, we report the development of two complimentary bioassays for evaluating the potency of newly developed antibiotic derivatives. The first assay is based on a liquid culture method. Micrococcus luteus cells are cultured in a 96-well plate in the presence of known concentrations of antibiotic. Antibiotic potency is quantified by comparison to standard curve of optical density at 600 nm recorded with microplate reader. The second assay involves growing confluent lawns of M. luteus, in the presence of antibiotic-treated filter-paper discs. Diffusion of the antibiotic into the surrounding media creates an area of inhibition, which is recorded digitally and numerically integrated to calculate the cleared area. IC50 values of semisynthetic penicillins are then computed from standard curves. These complimentary bioassays allow for comparison of lab-synthesized and commercially available antibiotics and provide a standard quantitative approach to report their potency.