Abstract: PD12-01
Sources of Funding: National Institutes of Health: R01DK097362 and T32AI007528_x000D_ Urology Care Foundation Fellow_x000D_ American Society of Microbiology Career Development Grant_x000D_ MTRAC Mi-Kickstart Award_x000D_

Introduction

Both the physical and financial burdens of urinary tract infections (UTIs) are staggering. In the U.S. alone, UTIs result in an estimated societal cost of $5.1 billion. UTIs are primarily caused by uropathogenic Escherichia coli (UPEC) and 1 in 40 women experience chronic UTIs during their lifetime. Women experiencing at least two UTIs per year are often given antibiotics prophylactically. As anticipated, the rates of resistance to these antibiotics in UPEC strains have steadily risen over the past few decades, highlighting the need for new antibiotic scaffolds and therapeutic strategies to treat UTIs. Iron, an essential nutrient used as a co-factor in many biological processes, is restricted in the host environment. Notably, the primary site of UPEC infection, the bladder, has dramatically lower iron levels than the sera. It is not surprising then that UPEC strains deficient in iron acquisition are attenuated. Based on the requirement of iron for full virulence of UPEC and the need for new antibiotic drug scaffolds, the objective of this study was to identify novel natural products that inhibit wildtype UPEC growth in low iron conditions.

Methods

To identify novel scaffolds and validate bacterial iron acquisition as a viable therapeutic target, we screened 33,000 marine microbial-derived natural product extracts (NPEs) against an unmodified UPEC clinical isolate. This ensured that active hits are not susceptible to Gram-negative efflux pumps. The NPEs were collected from the supernatants of marine bacteria as complex mixtures. To identify the structures of the active molecules, marine bacteria were cultured on a large scale and pure molecules were isolated from the NPEs using column chromatography and HPLC. The structures were elucidated using high-resolution mass spectrometry and 2-D NMR.

Results

We identified 204 NPEs that reduce wildtype UPEC growth in low iron by over 90% without chelating iron or impacting bacterial viability in iron-replete medium. From these hits, we have purified a novel family of cyclic natural products that inhibit bacterial growth at nanomolar concentrations. Preliminary data suggest that these small molecules are interfering with iron acquisition machinery.

Conclusions

These exciting data provide the foundation for exploring the structure-activity relationships of these compounds with their bacterial targets, which will inform the development of antimicrobial therapies that target iron homeostasis in UPEC and other Gram-negative bacteria.

Funding

National Institutes of Health: R01DK097362 and T32AI007528_x000D_ Urology Care Foundation Fellow_x000D_ American Society of Microbiology Career Development Grant_x000D_ MTRAC Mi-Kickstart Award_x000D_