Neisseria gonorrhoeae infection is treated with cephalosporins, antibiotics that target outer-membrane penicillin-binding proteins (PBPs), such as PBP1 and PBP2. Mutations in PBPs have led to the rapid development of antibiotic resistance, rendering many cephalosporin treatments ineffective. Despite being a major resistance mechanism, the nature of mutated PBP and drug interactions has yet to be characterized in a conclusive or reproducible manner with whole membrane or pathogen models. Therefore, we sought to identify binding relationships between antibiotic-resistant PBP variants and cephalosporins. We incubated cephalosporins, cefoxitin, ceftriaxone, and cefdinir, with purified PBPs and fluorescent Bocillin, allowing us to visualize the degree of cephalosporins binding using gel electrophoresis and fluorescent imaging. Cefoxitin inhibits PBP1 only, with no effect on PBP2, while ceftriaxone displayed inhibition of both PBP1 and PBP2, with greater influence on PBP1. Cefdinir only displayed inhibition of PBP1 and PBP2 at high concentrations. Based on these results, the ability of ceftriaxone and cefoxitin to synergistically inhibit growth was assessed using Minimum Inhibitory Concentration protocols. Cefoxitin did not significantly change the ability of ceftriaxone to inhibit growth. These results validated the use of purified PBP models to understand the mechanism of individual drugs against antibiotic-resistant strains, but are limited in ability to describe pathogen behavior, especially in an environment with multiple antibiotics.
Sophia Lavigne (Sat,) studied this question.