Benzimidazole Isosteres of Salicylanilides Are Highly Active Colistin Adjuvants

Validation of a Cystic Fibrosis Co-Culture Model for the Identification of Dual Acting Compounds with Antibiotic and Antibiotic Adjuvant Properties

Infections in the lungs of cystic fibrosis (CF) patients are often polymicrobial in nature, typically comprising Pseudomonas aeruginosa and Staphylococcus aureus. Compounds that act as an antimicrobial agent against one of these pathogens, and as an antibiotic adjuvant against the other, could provide a valuable approach to treating such infections, however a model that mimics the unique environment found with the CF lung is required for the identification and characterization of such molecules. To address this, we employed a S. aureus/P. aeruginosa coculture screening model in synthetic sputum, and identified compounds from our in-house library that simultaneously have potent anti-S. aureus activity, and potentiate colistin against colistin-resistant P. aeruginosa. The two lead compounds, 12F1 and 12G9, control growth of both species when dosed alongside sub-inhibitory concentrations of colistin, highlighting the potential of using a single molecule as both an antibiotic and antibiotic adjuvant to target multiple species in polymicrobial infections, as well as the importance of conducting activity screens in clinically relevant media.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2021-2022

The use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for the analysis of carbohydrates and glycoconjugates is a well-established technique and this review is the 12th update of the original article published in 1999 and brings coverage of the literature to the end of 2022. As with previous review, this review also includes a few papers that describe methods appropriate to analysis by MALDI, such as sample preparation, even though the ionization method is not MALDI. The review follows the same format as previous reviews. It is divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of computer software for structural identification. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other general areas such as medicine, industrial processes, natural products and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. MALDI is still an ideal technique for carbohydrate analysis, particularly in its ability to produce single ions from each analyte and advancements in the technique and range of applications show little sign of diminishing.

Adjuvants restore colistin sensitivity in mouse models of highly colistin-resistant isolates, limiting bacterial proliferation and dissemination

Antimicrobial resistance (AMR) has led to a marked reduction in the effectiveness of many antibiotics, representing a substantial and escalating concern for global health. Particularly alarming is resistance in Gram-negative bacteria due to the scarcity of therapeutic options for treating infections caused by these pathogens. This challenge is further compounded by the rising incidence of resistance to colistin, an antibiotic traditionally considered a last resort for the treatment of multi-drug resistant (MDR) Gram-negative bacterial infections. In this study, we demonstrate that adjuvants restore colistin sensitivity in vivo. We previously reported that the salicylanilide kinase inhibitor IMD-0354, which was originally developed to inhibit the human kinase IKKβ in the NFκB pathway, is a potent colistin adjuvant. Subsequent analog synthesis using an amide isostere approach led to the creation of a series of novel benzimidazole compounds with enhanced colistin adjuvant activity. Herein, we demonstrate that both IMD-0354 and a lead benzimidazole effectively restore colistin susceptibility in mouse models of highly colistin-resistant Klebsiella pneumoniae and Acinetobacter baumannii-induced peritonitis. These novel adjuvants show low toxicity in vivo, significantly reduce bacterial load, and prevent dissemination that could otherwise result in systemic infection.

Sulfonamide Bioisosteres of Niclosamide Enhance Antibacterial Activity of Colistin and Bacitracin

Multicomponent therapy combining antibiotics with enhancer molecules known as adjuvants is an emerging strategy to combat antimicrobial resistance. Niclosamide is a clinically relevant anthelmintic drug with potential to be repurposed for its inherent antibacterial activity against Gram-positive bacteria and its ability to potentiate the antibacterial activity of colistin against susceptible and resistant Gram-negative bacteria. Herein, sulfonamide analogs of niclosamide were prepared and found to enhance colistin activity against Gram-negative bacteria. The ability of niclosamide and the new sulfonamide analogs to synergize with bacitracin against vancomycin-resistant Enterococcus faecium was also discovered.

Exploring Structure-Activity Relationships of Niclosamide-Based Colistin Potentiators in Colistin-Resistant Gram-Negative Bacteria

Colistin is primarily used as a last resort antibiotic against highly resistant Gram-negative bacteria (GNB). Rising rates of colistin resistance, however, may limit future use of this agent. The anthelmintic drug niclosamide has been shown to enhance colistin activity in combination therapy, but a detailed structure-activity relationship (SAR) for niclosamide against GNB has yet to be studied. A series of niclosamide analogs were synthesized to perform an SAR, leading to the discovery of a lead compound that displayed comparable colistin-potentiating activity to niclosamide with reduced cytotoxicity. Overall, this work provides important insights into synthetic strategies for the future development of new niclosamide derivatives and demonstrates that toxicity to mammalian cells can be reduced while maintaining colistin potentiation.

6-Bromoindirubin-3'-oxime derivatives are highly active colistin adjuvants against Klebsiella pneumoniae

Multidrug resistant (MDR) bacterial infections have become increasingly common, leading clinicians to rely on last-resort antibiotics such as colistin. However, the utility of colistin is becoming increasingly compromised as a result of increasing polymyxin resistance. Recently we discovered that derivatives of the eukaryotic kinase inhibitor meridianin D abrogate colistin resistance in several Gram-negative species. A subsequent screen of three commercial kinase inhibitor libraries led to the identification of several scaffolds that potentiate colistin activity, including 6-bromoindirubin-3'-oxime, which potently suppresses colistin resistance in Klebsiella pneumoniae. Herein we report the activity of a library of 6-bromoindirubin-3'-oxime analogs and identify four derivatives that show equal or increased colistin potentiation activity compared to the parent compound.