Signal Biosynthesis Inhibition with Ambuic Acid as a Strategy To Target Antibiotic-Resistant Infections

• Published in: Antimicrobial agents and chemotherapy Vol. 61; no. 8
• Main Authors: Todd, Daniel A, Parlet, Corey P, Crosby, Heidi A, Malone, Cheryl L, Heilmann, Kristopher P, Horswill, Alexander R, Cech, Nadja B
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 01.08.2017
• Subjects: Animals; Anti-Bacterial Agents; Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - pharmacology; Bacterial Proteins; Bacterial Proteins - biosynthesis; Biologic Response Modifiers; Cyclohexanones; Cyclohexanones - chemistry; Cyclohexanones - pharmacology; Disease Models, Animal; Gram-Positive Bacteria; Gram-Positive Bacteria - drug effects; Gram-Positive Bacteria - genetics; Gram-Positive Bacteria - pathogenicity; Gram-Positive Bacterial Infections; Gram-Positive Bacterial Infections - drug therapy; Gram-Positive Bacterial Infections - microbiology; Humans; Male; Methicillin-Resistant Staphylococcus aureus - drug effects; Methicillin-Resistant Staphylococcus aureus - genetics; Methicillin-Resistant Staphylococcus aureus - pathogenicity; Mice; Mice, Inbred BALB C; Peptides, Cyclic; Peptides, Cyclic - biosynthesis; Quorum Sensing - drug effects; Signal Transduction; Staphylococcal Infections - drug therapy; Staphylococcal Infections - microbiology; Virulence Factors; inhibitors; ambuic acid; Agr system; virulence regulation; Staphylococcus aureus
• DOI: 10.1128/AAC.00263-17
• ISSN: 0066-4804

There has been major interest by the scientific community in antivirulence approaches against bacterial infections. However, partly due to a lack of viable lead compounds, antivirulence therapeutics have yet to reach the clinic. Here we investigate the development of an antivirulence lead targeting quorum sensing signal biosynthesis, a process that is conserved in Gram-positive bacterial pathogens. Some preliminary studies suggest that the small molecule ambuic acid is a signal biosynthesis inhibitor. To confirm this, we constructed a methicillin-resistant (MRSA) strain that decouples autoinducing peptide (AIP) production from regulation and demonstrate that AIP production is inhibited in this mutant. Quantitative mass spectrometric measurements show that ambuic acid inhibits signal biosynthesis (50% inhibitory concentration [IC ] of 2.5 ± 0.1 μM) against a clinically relevant USA300 MRSA strain. Quantitative real-time PCR confirms that this compound selectively targets the quorum sensing regulon. We show that a 5-μg dose of ambuic acid reduces MRSA-induced abscess formation in a mouse model and verify its quorum sensing inhibitory activity Finally, we employed mass spectrometry to identify or confirm the structure of quorum sensing signaling peptides in three strains each of and and single strains of , , , and By measuring AIP production by these strains, we show that ambuic acid possesses broad-spectrum efficacy against multiple Gram-positive bacterial pathogens but does not inhibit quorum sensing in some commensal bacteria. Collectively, these findings demonstrate the promise of ambuic acid as a lead for the development of antivirulence therapeutics.