Quantifying the Effects of Antibiotic-Loaded Nanodevices to Treat Chlamydial Infections

Abstract

Chlamydia trachomatis is an obligate intracellular bacterial pathogen. There are over one million new sexually transmitted chlamydial infections in the US each year. An arrest from the normal Chlamydial developmental cycle called persistence is associated with inflammatory arthritis (reactive arthritis) in both genders and infertility in women, and can occur if the bacteria spread to joints. Azithromycin is the most common antibiotic for chlamydial infections, but recent clinical studies showed that combination antibiotics were more effective for chlamydial reactive arthritis. We used cell culture models to test the efficacy of antibiotic delivery by nanodevices (antibiotics conjugated to dendrimers or inside nanoparticles). To compare nano-delivered drugs to free drugs on reduction of Chlamydia, we performed dose-response experiments, analysis of chlamydial inclusion size and we measured chlamydial 16S ribosomal DNA by qPCR. Polyamidoamine (PAMAM) dendrimer-conjugated Azithromycin was compared to free Azithromycin in acute and persistent in vitro infections. The same methods were applied to test Azithromycin and Rifampicin encapsulated together in poly(d-L-lactide-co-glycolide) PLGA nanoparticles (NP) compared to a free combination of these drugs. Our results indicated that NP-delivered combination antibiotics significantly reduced chlamydial infections in all experiments more effectively than free combination drugs. Dendrimer-Azithromycin proved significantly more effective than free drug in dose response acute infections, inclusion size analysis of acute and persistent infection, and qPCR of persistent infection. Combination drugs in NP appeared superior to other treatments for reduced chlamydial DNA in acute and persistent infection, but combination drugs on dendrimers have not been tested. Our results suggest new therapeutic strategies for treatment of Chlamydial infections, which we will test in the lab’s mouse models of Chlamydial infection in the near future.