ACS Infectious Diseases最新文献

Emerging evidence has demonstrated the importance of pattern recognition receptors (PRRs), including the nucleotide-binding and oligomerization domain receptor 2 (NOD2), in human health and disease states. NOD2 activation has shown promise with aiding malnutrition recovery, lessening irritable bowel disease (IBD) symptoms, and increasing the efficacy of cancer immunotherapy. Currently, most NOD2 agonists are derivatives or analogs of the endogenous agonist derived from bacterial peptidoglycan, muramyl dipeptide (MDP). These MDP-based agonists can suffer from low oral bioavailability and cause significant adverse side effects. With the goal of broadly improving NOD2 therapeutic interventions, we sought to discover a small molecule capable of activating NOD2 by screening a library of total 1917 FDA approved drugs in a phenotypic assay. We identified a class of compounds, benzimidazoles, that act as NOD2 agonists, with the most potent member of this class being nocodazole. Nocodazole activates NOD2 with nanomolar potency and causes the release of cytokines canonically associated with MDP-induced NOD2 activation, suggesting its potential to elicit similar therapeutic immune effects as MDP and potentially offer improved pharmacological properties.

The increase in the level of antibiotic-resistant Staphylococcus aureus underscores the urgent need for novel therapeutics. Consequently, repurposing clinically approved drugs has emerged as a compelling and time-saving strategy to counteract this escalating antimicrobial crisis. Here, high-throughput screening revealed that GSK2018682, an agonist of sphingosine-1-phosphate receptors S1P1 and S1P5, exhibits potent, broad-spectrum antimicrobial activity, particularly against S. aureus (MIC = 25–50 μM) and E. faecalis (MIC = 12.5–25 μM). GSK2018682 exhibited concentration-dependent bactericidal activity against both MSSA and MRSA, eradicating planktonic S. aureus within 6 h at 4× MIC. At sub-MIC concentrations, GSK2018682 significantly inhibited biofilm formation, and at 4× MIC, it killed the bacterial cells embedded in mature biofilms. Proteomics revealed that GSK2018682 caused global expression perturbations of functional proteins involved in a two-component system, various metabolic pathways, ribosomal functions, and biofilm regulatory factors (e.g., pflB, sarA). Drug Affinity Responsive Target Stability (DARTS) experiments implicated icaB (a PNAG deacetylase) and phospholipid synthase SAOUHSC_01260 as its candidate targets. Furthermore, GSK2018682 could increase membrane permeability, depolarize, and enhance fluidity to disrupt the S. aureus membranes. Exogenous phospholipid supplementation markedly attenuated the antibacterial efficacy of GSK2018682 against S. aureus. Finally, GSK2018682 displayed a strong efficacy in murine models of MRSA infection. In summary, our findings establish GSK2018682 as a promising anti-S. aureus agent with dual antibacterial and antibiofilm activities, acting through interaction with membrane phospholipids to disrupt membrane integrity and offering a strategy against resistant S. aureus infections.

The overuse of conventional antibiotics has enhanced the development of multidrug-resistant bacteria, which necessitates the development of innovative alternatives to combat bacterial infections. Antibacterial photodynamic therapy has emerged as a promising approach for the treatment of bacterial infections by inducing oxidative stress via reactive oxygen species generation. Recently, progress has been made in designing nanomaterial-based photoactive drugs that harness light to generate oxidative stress, effectively destroying bacterial cells upon irradiation. In this study, complex IrL¹ stands out as a photodynamic antimicrobial chemotherapeutic agent. IrL¹ self-assembled in culture media and demonstrated selective activity against Gram-positive Staphylococcus aureus with a minimum inhibitory concentration (MIC) value of 1 μg mL^–1 in the dark and 0.5 μg mL^–1 when irradiated with 390 nm light. It exhibited significant efficacy against methicillin-resistant S. aureus (MRSA) and vancomycin-resistant S. aureus (VRSA), as evidenced by MIC values ranging from 2 μg/mL. Upon irradiation, it induced oxidative stress by producing ¹O₂ and damaged the bacterial cell wall, as demonstrated by SEM and AFM imaging studies, which leads to cell death. Docking studies revealed its targeting of topoisomerase II DNA gyrase (binding energy = −14.33 kcal/mol, k_i = 31.15 pM), essential for bacterial survival. Time–kill assays and drug resistance studies reinforced its antimicrobial potential, and an in vivo evaluation demonstrated its therapeutic promise. Furthermore, the previously reported photodynamic anticancer properties of IrL¹ make it a compelling candidate for integrated therapeutic strategies, especially for cancer patients who are highly vulnerable to bacterial infections due to compromised immunity.

The natural product fidaxomicin (Fdx) is a narrow-spectrum antibiotic clinically prescribed for the treatment of Clostrodioides difficile infections. However, limited cellular uptake reduces its therapeutic potential, particularly against Gram-negative bacteria and mycobacteria. In this study, we investigated Thiol-Mediated Uptake (TMU) to promote the delivery of Fdx into bacterial cells. We synthesized a library of Fdx derivatives bearing cyclic dichalcogenide moieties and evaluated their antimicrobial properties against C. difficile and Mycobacterium tuberculosis, respectively. Remarkably, the synthetic Fdx derivatives retained strong levels of antibacterial activity, and the disulfide-containing analogs outperformed their all-carbon control counterparts in many instances. We then developed a systematic study to investigate the mechanistic impact of the introduced disulfide functionalities by conducting experiments with TMU inhibitors and quantifying intracellular accumulation in Mycobacterium bovis BCG, a model organism for M. tuberculosis, via LC-MS/MS. While complete disentanglement of the factors influencing activity was not feasible, features such as compound stability and lipophilicity were identified as significant contributors. Overall, the superior performance of disulfide analogs suggests that differences in cellular entry or intracellular processing, potentially related to TMU, are involved. This work highlights that TMU remains a viable approach for modulating the uptake of therapeutic agents into bacterial cells.

Chagas disease remains a significant global health concern, with current therapies limited to benznidazole and nifurtimox, which have adverse effects and show reduced efficacy in the chronic phase. This study investigated ruthenium complexes with or without thiobenzamide (Tbz). FOR0012A and FOR0212A, both containing Tbz, showed potent trypanocidal activity, with IC₅₀ values of 0.13 and 0.09 μM for trypomastigotes, and 1.8 and 0.32 μM for amastigotes. Electron microscopy revealed shrinkage, blebbing, and severe mitochondrial/kinetoplast damage, indicating apoptosis-like cell death, as confirmed by flow cytometry. Docking studies demonstrated strong binding to trypanothione reductase, suggesting oxidative stress induction, further supported by mitochondrial superoxide production and membrane depolarization. In a murine model, FOR0212A (20 mg/kg) reduced parasitemia by 50.2% during the acute phase without any toxicity. These findings identify FOR0212A as a promising therapeutic candidate for Chagas disease, acting via oxidative stress and apoptosis-like mechanisms in T. cruzi.

The cell envelope is an oft-cited factor in the ability of mycobacteria to tolerate antibiotics, host immunity, and environmental stress. In vitro studies have led to a prevailing model in which the mycobacterial envelope exhibits low fluidity that hinders the entry of antibiotics and other stressors. While membrane fluidity affects essential processes and is dynamically regulated across all domains of life, few studies have measured membrane fluidity in live mycobacteria. To address this gap, we used the environmentally sensitive probe C-Laurdan to develop an imaging- and flow cytometry-based method for measuring cell envelope fluidity directly in live cells. Our approach enables cell envelope labeling across diverse mycobacterial species, including M. smegmatis and M. tuberculosis. We characterized fluidity as a function of subcellular localization, antibiotic treatment, and genetic perturbation. The unusual growth characteristics of mycobacteria, including polar growth and asymmetric growth and division, contribute to intercellular heterogeneity that is thought to enhance survival under stress. Indeed, we observed that the poles are more fluid than sidewalls, and that the old pole is more fluid than the new pole. Further, daughter cells have unequal membrane fluidity upon division and this asymmetry is reduced in a mutant with decreased asymmetric polar growth. Chemical or genetic disruption of the mycomembrane led to a shared alteration of the fluidity pattern and susceptibility to two antibiotics, suggesting that membrane fluidity signatures may predict antibiotic susceptibility. This approach expands the toolkit for assessing fluidity in mycobacteria and enables deeper investigation into how biophysical properties influence bacterial physiology and antibiotic susceptibility.

Globally, diarrhea is the third leading cause of death in children below the age of five and is an acute problem in low- and middle-income countries (LMICs), where there is inadequate hygiene, poor sanitation, and a lack of access to clean drinking water. Infectious agents, such as bacteria, viruses, and protozoa, are primarily responsible for causing diarrhea. Despite significant progress in research over the past few decades, there are no licensed vaccines for most of these pathogens. Further, the growing problem of antimicrobial resistance has complicated treatment options. In this review, we provide an overview of the distinct yet often overlapping pathogenesis mechanisms employed by the diverse enteropathogens prevalent in the Global South. Future research should aim to exploit these mechanisms for the design of effective therapeutics and vaccines.

A bromoindazole was reported with the ability to rapidly and extensively kill Mycobacterium tuberculosis (Mtb) in vitro, but only in the presence of sublethal levels of reactive nitrogen species (RNS) (Warrier et al., ACS Infectious Diseases 1:585–560, 2015). After learning that that compound was poorly tolerated in mice, we identified a diaryl-aminoindazole with even more pronounced ability to kill Mtb in vitro in an RNS-dependent manner, along with RNS-dependent mycobactericidal activity against Mycobacterium avium and RNS-dependent mycobacteristatic activity against Mycobacterium abscessus. The compound was orally bioavailable and well tolerated in mice. However, 4- to 8-week treatment of mice with the diaryl-aminoindazole did not reduce their pulmonary burden of Mtb. Possible explanations include the low levels of compound detected in plasma at trough and the low levels of RNS detected in the lungs of these mice.

AdeFGH and AdeIJK, the two homologous multidrug efflux pumps of the resistance-nodulation-division superfamily of transporters, play distinct roles in Acinetobacter baumannii physiology and antibiotic resistance. Unlike ubiquitous AdeIJK, AdeFGH is strain-specific, typically expressed at low levels, and if overproduced, it enables resistance to a narrow spectrum of antibiotics, e.g., fluoroquinolones or chloramphenicol. In this study, we report that representatives of naphthyl-substituted diaminoquinolines targeting AdeIJK are also active against AdeFGH. We isolated AdeFGH-overproducing strains from the clinical AYE and Ab5075 isolates lacking AdeIJK and AdeABC pumps and demonstrated that these inhibitors are active in A. baumannii strains with different genetic backgrounds. The inhibitors potentiate the antibacterial activities of various antibiotics and enhance the bactericidal properties of the fluoroquinolones. We further analyzed how amino acid substitutions in the substrate translocation tunnels of AdeG affect the efflux properties of this pump and its sensitivity to inhibitors and compared them to the analogous substitutions in AdeJ. Our results suggest that the inhibitors engage similar contacts within the deep binding pockets of the two pumps but differ in their interactions in the entrance and the proximal binding sites. We conclude that the broad-spectrum activities of the diaminoquinolines as well as other inhibitors likely arise from the interactions within the deep-binding pockets, but their specificity is determined in the proximal-binding sites of the pumps.