2023 40 B2

Antibiotic Resistance and Plasmids

By: MaryGracy Antony, Marisol Fermin Flores, Jacqueline Valentino

Department: Biology

Faculty Advisor: Dr. Pleuni Pennings

The mechanism by which a patient acquires a resistant infection is not well understood.A patient can acquire a resistant infection through either de novo evolution of resistance or transmitted resistance. Knowing the role of transmission and within-host evolution is important in designing effective prevention programs to prevent further occurrences of antibiotic resistance. Phylogenetic trees of bacterial genomes will be used to understand the roles of transmission and within-host or de-novo evolution of resistance. A phylogenetic model is created describing patient-to-patient transmission and de novo evolution in which the model looks into the clustering of antibiotic-resistant isolates in phylogenetic trees. Preliminary findings show that resistance to the antibiotic Gentamicin, was observed in isolated places on the phylogenetic tree, while, Amoxicillin resistance was observed in larger clades, which suggests transmission playing a bigger role. These results conclude that there is a difference in how easily antibiotic resistance is transmitted between drugs. However, not much is known about the effect of plasmid transmission and acquisition within resistant/susceptible bacteria, especially in a natural environment. Most studies on antibiotic drug resistance are done with strains cultured in a lab. These studies lack the selective pressures bacteria face in a natural environment, and thus fail in understanding the pathway in which resistance is acquired. Additionally, the studies do not reproduce the observed coexistence of drug sensitive (susceptible) and drug-resistant strains. The publicly available dataset (Kallonen et al., 2017) contains data from an extensive collection of susceptible and resistant E.coli isolates collected from patients for more than a decade. The dynamics of antibiotic resistance in clinical populations of E. coli will be unraveled through understanding the presence of plasmids in clades and phylogroups of different drugs.