Preclinical antimicrobial drug discovery : development and evaluation of a platform for high-throughput screening in vitro and an immunocompromised animal model

The incidence of infections caused by antibiotic-resistant bacteria and fungi is rising rapidly. Once considered as little more than a nuisance, antibiotic resistance has become a serious threat. The mortality rate for some infections is approaching that of the pre-antibiotic era. New antimicrobials are needed urgently. Prior to the introduction of any new antimicrobial, comprehensive toxicity and efficacy profiles are assessed in preclinical studies. This thesis focuses on two key stages of preclinical antimicrobial drug development, specifically compound screening in vitro and animal efficacy testing in vivo. We developed a sensitive colorimetric platform with high-throughput capacity for the rapid screening of candidate antimicrobials. This platform could be adapted to assess compounds targeting a range of bacteria, fungi (such as Candida albicans), and protozoan parasites (such as Leishmania major). When this assay was modified to measure minimum inhibitory concentrations (MICs) for bacteria, 100% agreement within one dilution was achieved compared to the gold-standard method. A novel antifungal compound was taken forward to animal testing in an immunocompromised mouse model. We demonstrated herein that a histone deacetylase inhibitor in combination with an imidazole can synergise to produce a potent antifungal effect. A dose-dependent response, defined as a lower fungal burden and a higher survival rate, was achieved with increasing concentrations of the novel inhibitor