Drug-resistant superbugs pose a huge threat to human health. Infections by Enterobacteriaceae producing metallo-β-lactamases (MBLs), e.g., New Delhi metallo-β-lactamase 1 (NDM-1) are very difficult to treat. Development of effective MBL inhibitors to revive the efficacy of existing antibiotics is highly desirable. However, such inhibitors are not clinically available till now. Here we show that an anti-Helicobacter pyloridrug, colloidal bismuth subcitrate (CBS), and related Bi(III) compounds irreversibly inhibit different types of MBLs via the mechanism, with one Bi(III) displacing two Zn(II) ions as revealed by X-ray crystallography, leading to the release of Zn(II) cofactors. CBS restores meropenem (MER) efficacy against MBL-positive bacteria in vitro, and in mice infection model, importantly, also slows down the development of higher-level resistance in NDM-1-positive bacteria. This study demonstrates a high potential of Bi(III) compounds as the first broad-spectrum B1 MBL inhibitors to treat MBL-positive bacterial infection in conjunction with existing carbapenems.

Ultra-selective and ultra-sensitive probes for hypochlorous acid (HOCl), one of the most poorly understood reactive oxygen species (ROS), are urgently needed to unravel the HOCl functions in important biological processes such as development and innate immunity. Based on a selective oxidative O-dearylation reaction of 2,6-dichlorophenol toward HOCl over other reactive oxygen species, we have developed a novel fluorescent probe HKOCl-3 for HOCl detection with ultra-selectivity, ultra-sensitivity and a rapid turn-on response. The functional robustness of HKOCl-3 for endogenous HOCl detection and imaging has been thoroughly scrutinized in multiple types of phagocytes and in vivo imaging of live intact zebrafish embryos. Furthermore, HKOCl-3 has been successfully applied to the detection of endogenous HOCl by a 96-well microplate assay and flow cytometry. Therefore, HKOCl-3 holds great promise as a versatile molecular tool that enables innovative investigation of HOCl biology and ROS-related diseases in multiple detection modalities.

Significance: The dissemination of antibiotic resistance in pathogenic bacteria is remarkable, and antivirulence agents with novel mechanisms of action could lead to innovative therapeutic concepts. The simultaneous suppression of multiple virulence factors or pathways using small-molecule compounds is an attractive approach to reducing the virulence of Staphylococcus aureus and may offer promising therapeutic potential in combating multidrug-resistant bacteria such as methicillin-resistant S. aureus . Here we describe a conceptual breakthrough in applying chemical genetics to probe for small-molecule compounds that will suppress the expression of multiple virulence factors in S. aureus simultaneously. Compound M21 has the ability to reverse virulent S. aureus to a nonvirulent state, as demonstrated in a mouse model of infection.

The natural products triptolide, withaferin A and celastrol have been discovered to be novel Prx I chaperone inhibitors using synthetic chemical probes.

Staphylococcus aureus, especially methicillin-resistantS. aureus(MRSA), is a life-threatening pathogen in hospital- and community-acquired infections. The golden-colored carotenoid pigment ofS. aureus, staphyloxanthin, contributes to the resistance to reactive oxygen species (ROS) and host neutrophil-based killing. Here, we describe a novel inhibitor (NP16) ofS. aureuspigment production that reduces the survival ofS. aureusunder oxidative stress conditions. Carotenoid components analysis, enzyme inhibition, andcrtNmutational studies indicated that the molecular target of NP16 is dehydrosqualene desaturase (CrtN).S. aureustreated with NP16 showed increased susceptibility to human neutrophil killing and to innate immune clearance in a mouse infection model. Our study validates CrtN as a novel druggable target inS. aureusand presents a potent and effective lead compound for the development of virulence factor-based therapy againstS. aureus.IMPORTANCES. aureusstaphyloxanthin contributes substantially to pathogenesis by interfering with host immune clearance mechanisms, but it has little impact onex vivosurvival of the bacterium. Agents blocking staphyloxanthin production may discourage the establishment and maintenance of bacterial infection without exerting selective pressure for antimicrobial resistance. Our newly discovered CrtN inhibitor, NP16, may offer an effective strategy for combatingS. aureusinfections.