ACS Infectious Diseases最新文献

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.

Phenotypic screening remains essential for identifying and characterizing bioactive compounds or their combinations against human parasitic pathogens. In the case of Trypanosoma cruzi, the etiological agent of Chagas disease, transgenic parasites expressing the reporter enzyme β-galactosidase have been extensively used to this end. Here, we replaced the traditional chromogenic substrate chlorophenol red-β-d-galactopyranoside (CPRG) with the fluorogenic 4-methylumbelliferyl-β-d-galactopyranoside (MUG) to derive a highly sensitive, continuous enzymatic assay to obtain a quantitative surrogate of parasite growth in T. cruzi cultures. The assay detects as few as 3 × 10³ trypomastigotes/well, tracks linearly with the parasite load in a two-order range (3 × 10³-2 × 10⁵ trypomastigotes/well), takes 1 h, and has a similar cost per assay as its colorimetric counterpart. To demonstrate its convenience and versatility, we used this assay to estimate the half-maximal inhibitory concentration (IC₅₀) of six emerging antifungal compounds, not targeting CYP-51 and novel for T. cruzi. Finally, the assay was adapted to a semiautomatic methodology and used to explore dual combinations of the active antifungals in the primary screening and with benznidazole. The multitarget compound AR-12 (IC₅₀ = 1.9 μM) and the Gwt1 inhibitor Fosmanogepix (IC₅₀ = 7.2 μM) resulted in bona fide hits, inhibiting parasite replication with only low-to-moderate toxicity on Vero host cells, thus suggesting potential for repurposing to Chagas disease.

Paracoccidioidomycosis (PCM) is a systemic fungal infection that primarily affects the lungs. Previous studies have shown that 5-fluorouracil (5-FU), a chemotherapeutic agent, reduces pulmonary myeloid-derived suppressor cells (MDSCs), thereby stimulating immune responses in PCM. This study aimed to evaluate the efficacy of the combined 5-FU and AmB therapy in a murine model of PCM. C57BL/6 mice were infected with Paracoccidioides brasiliensis and treated with AmB and/or 5-FU. We found that the 5-FU and AmB combination therapy led to improved disease control, as evidenced by reduced fungal burden, decreased tissue damage, and an increased survival rate. Moreover, the combined treatment was associated with decreased lymphocyte and neutrophil counts, along with an increased number of macrophages in pulmonary tissue, suggesting a controlled infectious process without hyperinflammatory reactions. These findings support the potential of combining 5-FU with conventional antifungal therapy as a promising strategy for enhancing PCM treatment outcomes.

Colonic microbiome dysbiosis is correlated with inflammatory bowel disease (IBD), and depletion of the commensal bacterium Faecalibacterium prausnitzii (F. prausnitzii) is routinely observed in the metagenomic analyses of IBD patient microbiome samples. F. prausnitzii is likely beneficial to hosts, as oral administration of F. prausnitzii strain A2–165 has anti-inflammatory properties in murine models of colitis. Previous studies attribute the anti-inflammatory effects of F. prausnitzii A2–165 to production of the short-chain fatty acid butyrate, as well as a secreted protein known as microbial anti-inflammatory molecule (MAM). Here, we verified that oral dosing of strain A2–165 protects against DSS-induced murine colitis and further showed that the aqueous-soluble secreted fraction of overnight cultures from a collection of F. prausnitzii strains inhibits inflammatory signatures, including the activation of the host’s NF-κB pathway, production of IL-8, and differentiation of naïve T cells into the T_H17 lineage. Our findings against a panel of in vitro assays suggested that the anti-inflammatory responses were attributable to secreted small-molecule or peptide metabolites, as both heat-inactivated and proteinase K-treated F. prausnitzii culture supernatants retained activity. Untargeted and targeted mass spectrometry metabolomics analyses on the soluble anti-inflammatory secretome yielded several unique F. prausnitzii metabolites, including isopentenyladenine. We demonstrated that isopentenyladenine independently modulates host cellular signaling and immune responses and suggest that this newly identified metabolite with human immunomodulatory properties may be useful toward the discovery of IBD-focused therapeutics.

Rapid, sensitive, and user-friendly nucleic acid diagnostics are critical for controlling outbreaks of Seneca Valley virus (SVA). Here, we present Field-deployable Isothermal Enzymatic Lysis Detection (FIELD), an RNA detection platform for resource-limited settings that integrates rapid detection, operational simplicity, and minimal equipment requirements. FIELD employs a room-temperature lysis protocol to release viral nucleic acids within 2 min, followed by a single-step RPA–CRISPR/Cas13d reaction completed in 30 min. FIELD detects SVA RNA at 8 copies/μL using a plate reader and at 50 copies/μL via visual readout within 35 min, with no cross-reactivity against nontarget viruses. FIELD remains functional at both body (∼37 °C) and room (∼25 °C) temperatures, eliminating the need for temperature-controlled devices. Lyophilized FIELD reagents retain full activity for 1 week at room temperature and remain functional after long-distance transport and storage at 4 °C for up to two months, supporting field deployment. In a clinical evaluation of 88 field samples, FIELD achieved 100% sensitivity and specificity relative to RT-qPCR. Collectively, these features render FIELD well suited for point-of-care testing (POCT) beyond conventional laboratory settings.

Global dissemination of genes conferring carbapenem and aminoglycoside resistance has put Klebsiella at the top of the World Health Organization’s list of critical priority pathogens. The burgeoning arsenal of aminoglycoside modifying enzymes (AMEs) and 16S rRNA methyltransferases (RMTases) threatens to render aminoglycosides ineffective. Drug combination therapy such as polymyxin and aminoglycoside amikacin has been indicated for drug-resistant Klebsiella infections. The goal of this study was to chemically synthesize and study the antibacterial activity for a novel peptide-linked amikacin library combined with polymyxin. Amikacin derivatives with amino acids containing a positive charge, containing sulfur or with aromatic side chains, were synergistic with polymyxin B against amikacin and pandrug-resistant bacteria. Of 31 Klebsiella pneumoniae strains screened with amikacin peptides containing tryptophan and cysteine with polymyxin, synergy was observed in 77% of strains, including those carrying multiple AME and RMTases. P-AMK compounds behave similarly to AMK, with or without PMB, in killing mammalian cells, but are much more synergistic (as compared to AMK) with PMB in killing drug-resistant bacterial cells.