Sensitization of Gram-Negative Bacteria to Aminoglycosides with 2-Aminoimidazole Adjuvants.

In 2019, five million deaths associated with antimicrobial resistance were reported by The Centers for Disease Control and Prevention (CDC). Acinetobacter baumannii, a Gram-negative bacterial pathogen, is among the list of urgent threats. Previously, we reported 2-aminoimidazole (2-AI) adjuvants that potentiate macrolide activity against A. baumannii. In this study, we identify several of these adjuvants that sensitize A. baumannii to aminoglycoside antibiotics. Lead compounds 1 and 7 lower the tobramycin (TOB) minimum inhibitory concentration (MIC) against the TOB-resistant strain AB5075 from 128 µg/mL to 2 µg/mL at 30 µM. In addition, the lead compounds lower the TOB MIC against the TOB-susceptible strain AB19606 from 4 µg/mL to 1 µg/mL and 0.5 µg/mL, respectively, at 30 µM and 15 µM. The evolution of resistance to TOB and 1 in AB5075 revealed mutations in genes related to protein synthesis, the survival of bacteria under environmental stressors, bacteriophages, and proteins containing Ig-like domains.

Advanced Glycation End Products as a Potential Target for Restructuring the Ovarian Cancer Microenvironment: A Pilot Study.

Ovarian cancer is the sixth leading cause of cancer-related death in women, and both occurrence and mortality are increased in women over the age of 60. There are documented age-related changes in the ovarian cancer microenvironment that have been shown to create a permissive metastatic niche, including the formation of advanced glycation end products, or AGEs, that form crosslinks between collagen molecules. Small molecules that disrupt AGEs, known as AGE breakers, have been examined in other diseases, but their efficacy in ovarian cancer has not been evaluated. The goal of this pilot study is to target age-related changes in the tumor microenvironment with the long-term aim of improving response to therapy in older patients. Here, we show that AGE breakers have the potential to change the omental collagen structure and modulate the peritoneal immune landscape, suggesting a potential use for AGE breakers in the treatment of ovarian cancer.

Dimeric 2-aminoimidazoles are highly active adjuvants for gram-positive selective antibiotics against Acinetobacter baumannii.

The Centers for Disease Control and Prevention (CDC) reports that hospital acquired infections have increased by 65% since 2019. One of the main contributors is the gram-negative bacterium Acinetobacter baumannii. Previously, we reported aryl 2-aminoimidazole (2-AI) adjuvants that potentiate macrolide antibiotics against A. baumannii. Macrolide antibiotics are typically used to treat infections caused by gram-positive bacteria, but are ineffective against most gram-negative bacteria. We describe a new class of dimeric 2-AIs that are highly active macrolide adjuvants, with lead compounds lowering minimum inhibitory concentrations (MICs) to or below the gram-positive breakpoint level against A. baumannii. The parent dimer lowers the clarithromycin (CLR) MIC against A. baumannii 5075 from 32 µg/mL to 1 µg/mL at 7.5 µM (3.4 µg/mL), and a subsequent structure activity relationship (SAR) study identified several compounds with increased activity. The lead compound lowers the CLR MIC to 2 µg/mL at 1.5 µM (0.72 µg/mL), far exceeding the activity of both the parent dimer and the previous lead aryl 2-AI. Furthermore, these dimeric 2-AIs exhibit considerably reduced mammalian cell toxicity compared to aryl-2AI adjuvants, with IC50s of the two lead compounds against HepG2 cells of >200 µg/mL, giving therapeutic indices of >250.

Augmenting the Activity of Macrolide Adjuvants against Acinetobacter baumannii.

Approximately 1.7 million Americans develop hospital associated infections each year, resulting in more than 98,000 deaths. One of the main contributors to such infections is the Gram-negative pathogen Acinetobacter baumannii. Recently, it was reported that aryl 2-aminoimidazole (2-AI) compounds potentiate macrolide antibiotics against a highly virulent strain of A. baumannii, AB5075. The two lead compounds in that report increased clarithromycin (CLR) potency against AB5075 by 16-fold, lowering the minimum inhibitory concentration (MIC) from 32 to 2 µg/mL at a concentration of 10 µM. Herein, we report a structure-activity relationship study of a panel of derivatives structurally inspired by the previously reported aryl 2-AI leads. Substitutions around the core phenyl ring yielded a lead that potentiates clarithromycin by 64- and 32-fold against AB5075 at 10 and 7.5 µM, exceeding the dose response of the original lead. Additional probing of the amide linker led to the discovery of two urea containing adjuvants that suppressed clarithromycin resistance in AB5075 by 64- and 128-fold at 7.5 µM. Finally, the originally reported adjuvant was tested for its ability to suppress the evolution of resistance to clarithromycin over the course of nine consecutive days. At 30 µM, the parent compound reduced the CLR MIC from 512 to 2 µg/mL, demonstrating that the original lead remained active against a more CLR resistant strain of AB5075.

Second-Generation Tryptamine Derivatives Potently Sensitize Colistin Resistant Bacteria to Colistin.

Antibiotic resistance has significantly increased since the beginning of the 21st century. Currently, the polymyxin colistin is typically viewed as the antibiotic of last resort for the treatment of multidrug resistant Gram-negative bacterial infections. However, increased colistin usage has resulted in colistin-resistant bacterial isolates becoming more common. The recent dissemination of plasmid-borne colistin resistance genes (mcr 1-8) into the human pathogen pool is further threatening to render colistin therapy ineffective. New methods to combat antibiotic resistant pathogens are needed. Herein, the utilization of a colistin-adjuvant combination that is effective against colistin-resistant bacteria is described. At 5 µM, the lead adjuvant, which is nontoxic to the bacteria alone, increases colistin efficacy 32-fold against bacteria containing the mcr-1 gene and effects a 1024-fold increase in colistin efficacy against bacteria harboring chromosomally encoded colistin resistance determinants; these combinations lower the colistin minimum inhibitory concentration (MIC) to or below clinical breakpoint levels (≤2 µg/mL).

Using Small-Molecule Adjuvants to Repurpose Azithromycin for Use against Pseudomonas aeruginosa.

A major contributor to fatalities in cystic fibrosis (CF) patients stems from infection with opportunistic bacterium Pseudomonas aeruginosa. As a result of the CF patient's vulnerability to bacterial infections, one of the main treatment focuses is antibiotic therapy. However, the highly adaptive nature of P. aeruginosa, in addition to the intrinsic resistance to many antibiotics exhibited by most Gram-negative bacteria, means that multi-drug-resistant (MDR) strains are increasingly prevalent. This makes the eradication of pseudomonal lung infections nearly impossible once the infection becomes chronic. New methods to treat pseudomonal infections are greatly needed in order to eradicate MDR bacteria found within the respiratory tract, and ultimately better the quality of life for CF patients. Herein, we describe a novel approach to combatting pseudomonal infections through the use of bis-2-aminoimidazole adjuvants that can potentiate the activity of a macrolide antibiotic commonly prescribed to CF patients as an anti-inflammatory agent. Our lead bis-2-AI exhibits a 1024-fold reduction in the minimum inhibitory concentration of azithromycin in vitro and displays activity in a Galleria mellonella model of infection.