Evolution of Resistant Mutants in Antibiotic Treated Bacterial Cultures

Bacterial Persisters are cells who undergo a phenotypic shift and enter a dormant state in order to tolerate new levels of stress. Persisters are present in every colony of bacteria and can cause chronic infections. Even when treatment is successful in killing bacteria and removing the patient’s symptoms, the persisters will eventually resuscitate and proliferate a new colony. Preliminary experiments done by my mentor suggested that Ofloxacin, a quinolone that affects cell replication and induces the cells DNA repair mechanisms, can cause random mutations in the genomic DNA of bacteria. My goal of this investigation was to enrich Escherichia coli cultures with antibiotic resistant mutants, for cross analysis with a parental strain and a Green Fluorescent Protein (GFP) producing strain. The purpose of this is to figure out if persisters are more important than resistant mutants. Our data demonstrates that persister cells do function as a reservoir for resistant mutants because of the increased survivors. This poses as a threat because some of the mutants were even able to withstand antibiotic treatment of ampicillin and gentamicin. In conclusion, these results suggest that novel anti-persister treatment will help with the battle against antibiotic resistance.