Due to a lack of novel antimicrobial development amongst other issues, antimicrobial resistance (AMR) has been flagged as one of the major threats to human health by the World Health Organisation. For Aspergillus fumigatus, a lack of specific and sensitive diagnostic assays increases the risk of the pathogen further. This thesis poses that the chemoderivatisation of siderophores, iron chelating molecules produced by microorganisms in response to iron starvation, could be used to develop novel antimicrobial treatments and diagnostic assays. Siderophore Trojan horse molecules are known to improve the uptake of antimicrobial compounds. An A. fumigatus secondary metabolite, gliotoxin (GT) is known to be an antimicrobial toxin, but is also cytotoxic. GT was modified and conjugated to an A. fumigatus siderophore, diacetylfusarinine C (FeDAFC), for use as an antimicrobial. A. fumigatus siderophores were further exploited for their diagnostic potential. Ferricrocin (FeFC) was used as a hapten and conjugated to a carrier-protein for immunisation. The resulting antisera was screened for antibodies against FeFC. Antibodies previously developed against Triacetylfusarinine C (FeTAFC) using a hapten immunogen strategy were used to develop a one-step ELISA for the detection of FeTAFC in urine, with high specificity. This antibody was then shown to have antifungal properties against A. fumigatus due to the binding of FeTAFC, which is essential for its growth and virulence, preventing uptake of the siderophore. A recombinant esterase, rEstB, for the breakdown of FeTAFC was produced and shown to have activity against FeTAFC, with the hope of development as a crop antimicrobial. Finally, a plant derived compound, celastrol, which has been linked to preventing the production of A. fumigatus siderophores, with coincubation with the novel compound ADL2022, was shown to have antimicrobial effects even under iron-replete conditions and to have a significant impact on the proteome of A. fumigatus.