Examining the Influence of the Nutritional Environment on Antibiotic Susceptibility of Pseudomonas aeruginosa

Antibiotic resistance is a crucial problem facing modern society as all pathogens inevitably evolve resistance to known antibiotics. However, the susceptibility of bacteria to existing antibiotics is only readily understood in select environmental contexts. The bacterium Pseudomonas aeruginosa has been shown to exhibit reduced susceptibility to aminoglycoside antibiotics when grown with moderate or low concentrations of calcium (Ca²⁺). This form of resistance has been linked to membrane-based two-component systems, which act as efflux pumps for the antibiotic when calcium is present. Other antibiotic classes, such as ß-lactams, are not known to be influenced by these efflux pumps. In this thesis, I explore the ability of calcium levels to influence antibiotic susceptibility when considering glucose or glutamate as carbon sources for bacterial growth. P. aeruginosa exhibited decreased susceptibility when exposed to gentamicin and ceftazidime and supplemented with calcium and glutamate. These trends were not observed with ciprofloxacin.