Studies On Characterization And Inhibition Of Metallo-β-lactamases And Function Of Fluorescent Antibiotics For Photodynamic Inactivation Of Bacteria

Antibiotic resistance is very ancient. With the discovery and usage of antibiotics in the clinic, it promotes the spread of resistance, and results into so many resistant bacteria, including the superbugs. Now, antibiotic resistance in bacteria is a growing biomedical crisis all over the world. In this dissertation, metallo-p-lactamase (MPL) LI from Stenotrophomonas maltophilia was successfully overexpressed, purified, characterized by kinetic, spectroscopic, and TG-DSC studies, and labeled with chlorinated fluorescein. Furthermore, determination of thermokinetic parameters of penicillin G hydrolysis catalyzed by L1was first reported, and would be helpful to search broad-spectrum inhibitors of MβLs. In this area, searching broad-spectrum inhibitors of MβLs is always difficult and hot spot. Camphor and thioacetate were chosen as the potential inhibitors to carry out research, but the result indicated that neither of them could effectively inhibit the representative MβLs CcrA (B1subgroup), ImiS (B2subgroup), and L1(B3subgroup). When the traditional therapies failed to fight against resistant bacteria, a new and novel therapy-photodynamic therapy was used to inactivate resistant bacteria. Three kinds of fluorescent antibiotics, fluorescein-cephalothin IV, fluorescein-kanamycin (KanF), and fluorescein-norvancomycin (VanF), were synthesized as photosensitizers. VanF could successfully label bacteria, and produce the singlet oxygen (1O2) to inactivate Bacillus subtilis. When the concentration of VanF was7.5μM, the bacterial lethality reached to70%.