The Discovery of New Antibiotics from Deep Sea Actinomycete Bacteria

This application seeks to establish a collaborative program in marine antibiotic drug discovery headed by William Fenical from the Scripps Institution of Oceanography in association with Victor Nizet from the Schools of Medicine & Pharmacy, both faculty researchers at the University of California, San Diego. The program capitalizes on the recent discovery that new, genetically-diverse and chemically-rich actinomycete bacteria, the classic resource for antibiotics, reside in deep-ocean sediments. The program emphasizes innovative immunological and virulence factor-based approaches in anti-infective drug screening coupled with tried and true whole cell bioassay methods for bacteriostatic and bactericidal activities. <P> The overall goal of this research program is to merge the marine microbiology and natural products chemistry expertise of the Fenical lab with the molecular microbiology and infectious disease expertise of the Nizet lab to establish a unique and long-term collaboration to discover new antibiotics effective against drug-resistant bacterial and fungal pathogens. <P> To achieve this goal, a step-wise discovery and development program will be set in place that emphasizes the discovery of new molecules with unprecedented structures and significant in vivo activity. The program will focus on screening marine actinomycete culture extract fractions (more than 3,500 per year) against drug-resistant human pathogens of immediate concern, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecalis (VREF), Pseudomonas aeruginosa, multi drug-resistant Acinetobacter baumannii, and fluconazole-resistant Candida albicans. In addition, innovative, non-cell-kill assays will be involved, which include inhibition of two critical virulence factors of the leading bacterial pathogens, the golden carotenoid pigment of S. aureus, the pore-forming cytolytic toxin streptolysin S of group A Streptococcus (GAS), as well as an assay to boost the host innate immune function via induction of the global transcriptional regulator HIF-1 in macrophages and neutrophils. New antibiotics will be isolated, structurally defined and screened in vitro against an expanded panel of more than 35 other human pathogens. When sufficiently potent antibiotics are defined, they will be advanced to murine in vivo assay systems for therapeutic efficacy in systemic and localized infection models for MRSA (for classical antibiotic), HIF-1 (innate immune enhancement or pigment inhibition agents) or GAS (for SLS inhibition agents) with which the Nizet laboratory has extensive experience. Up to ten of the most promising new antibiotics will also undergo a limited number of more advanced preclinical evaluations including acute mouse toxicity, kinetics of antimicrobial effect, capacity for resistance development, and post-antibiotic effect. Compounds that meet the stringent requirements to be considered drug candidates will be advanced to collaborating industries or developed within UCSD through spin-off projects.<P> PUBLIC HEALTH RELEVANCE. The continued emergence of drug-resistant infectious diseases has created a National health care emergency to which the approximately 2 million people acquire bacterial infections in U.S. hospitals each year, and 90,000 die as a result; approximately 70% of those infections are resistant to at least one drug. This application establishes a collaborative program between laboratories with expertise in (A) marine science and natural product chemists and (B) bacterial pathogenesis and infectious disease. The team will discover and characterize novel antibiotics from deep ocean marine microbes that are effective against several drug-resistant bacterial and fungal pathogens, thus providing heath care practitioners with critical new approaches to infectious disease therapy.