ACS Infectious Diseases

Many commonly prescribed non-antibiotic medicines have off-target antimicrobial activity, yet their impact on antibiotic efficacy remains poorly understood. In this study, we investigated eight widely used UK prescription medicines and identified simvastatin, amlodipine, and fluoxetine as growth inhibitory towards methicillin-resistant Staphylococcus aureus (MRSA). These drugs disrupt bacterial membranes, with amlodipine and fluoxetine also triggering stress responses linked to cell wall and membrane damage. Further mechanistic analysis using transposon mutant screening revealed that simvastatin impairs cell wall synthesis by inhibiting the mevalonate pathway. Notably, checkerboard assays demonstrated antagonistic interactions: simvastatin reduced the efficacy of {beta}-lactams and vancomycin, amlodipine with vancomycin and daptomycin, and fluoxetine with vancomycin activity. Prolonged exposure to these drugs also accelerated resistance development to vancomycin and daptomycin. Together, these findings underscore the potential for commonly prescribed non-antibiotic medicines to undermine antibiotic therapy, warranting further study given the rising S. aureus treatment failures.

Macrolides are an antibiotic class widely used in both human and veterinary medicine, and function by interfering with protein synthesis. Regrettably, numerous strategies for evading the antibiotic properties of macrolides have been found in bacteria, including enzyme-mediated inactivation. These mechanisms are now widely disseminated among pathogenic, animal-associated and environmental bacteria making them a One Health issue. Macrolide esterases, which hydrolyze the macrolactones ester bond, confer one such resistance mechanism. Two types of macrolide esterases have thus far been identified, the well-studied erythromycin esterases and the recently discovered Est-type enzymes that belong to the /{beta}-hydrolase superfamily. We present detailed structure-function studies for four diverse Est type esterases: which only share 44-66% sequence identity (EstTSf, EstTSt, EstTBc, and EstXEc). In addition to resistance profiling and substrate specificity studies, we present structures for all four enzymes, including structures for EstTBc and EstXEc in complex with tylosin and tylvalosin macrolides, post hydrolysis. Complementing the data with mutational and kinetic studies allowed for a detailed analysis of the structural basis for macrolide-enzyme interactions. Combined the data suggest that promiscuous binding and imprecise positioning, mediated by a water-cage, dictate substrate specificity for Est-type macrolide resistance enzymes. These insights may prove beneficial for next-generation antibiotic development.

Antimicrobial resistance is an impactful One Health issue. One of its drivers is the extensive use of antibiotics in both human and animal production systems, and despite regulatory restrictions on antibiotic use in poultry farming, antimicrobial resistance remains a major challenge. Consequently, animals are at higher risk of harder-to-treat diseases and play a role as resistance reservoirs, highlighting the need for alternative antimicrobial strategies. Towards this end, antimicrobial peptides (AMPs) have emerged as promising candidates due to their broad-spectrum activity and lower propensity to induce resistance. However, the effectiveness of AMPs against poultry pathogens, and in particular multi drug-resistant strains, is largely unclear. To tackle this question, we evaluated the synthetic AMP SET-M33 against four species of clinically relevant pathogens in poultry, namely Escherichia coli, Salmonella enterica, Enterococcus faecalis and Enterococcus cecorum. Using a panel of 141 field isolates, we found that SET-M33 broadly inhibited bacterial growth at low micromolar concentrations (median MICs of 2.5 M and 5 M for Gram-negative and Gram-positive strains, respectively), including in multi drug-resistant isolates. To examine the potential impact of SET-M33 on the host, we established a new in vitro co-cultivation system using chicken intestinal organoids. We found that SET-M33 retains its antimicrobial activity in organoid-microbe co-cultures at concentrations that preserved host viability. These findings demonstrate the potential of SET-M33 as a new antimicrobial agent against pathogens in poultry.

Tuberculosis, often considered the worlds deadliest infectious disease, is associated with over one million deaths annually. The emergence of drug-resistant strains of Mycobacterium tuberculosis (Mtb) makes anti-tuberculosis drug development a critical priority. Griselimycin (GM) is a cyclic peptide that targets the essential DNA sliding clamp of Mtb. While GM is a promising Mtb antibiotic, its poorly understood structure-activity relationship has stalled derivatization. To investigate the contribution of each amino acid towards its activity, we assessed the antibiotic activity of an alanine scan library in M. tuberculosis and M. smegmatis. Residues essential for activity and tolerable to modification were identified, and the impact of backbone N-methylation at each position was determined. Edits to cyclization chemistry, unnatural amino acid incorporation, and replacing the acetylated N-terminus with a free amine were also investigated. Lastly, incorporation of an N-terminal fluorophore enabled visualization of GM accumulation inside of mycobacteria both in and outside of macrophage cells, where Mtb natively resides. These findings present the first comprehensive structure-activity investigation into GM and can be used to rationally design future analogues.

Protein synthesis represents an attractive target space for the development of anti-malarials with novel modes of action. Natural-product inhibitors of the eukaryotic 80S ribosome can have potent anti-malarial activity but are often poorly selective due to mammalian cytotoxicity. Blasticidin S (BlaS) is a microbially-produced natural product that broadly inhibits prokaryotic and eukaryotic protein synthesis by binding to the ribosomal peptidyl transferase center. In this study, we explored the potential for improving the anti-malarial potency and selectivity of the blasticidin S scaffold with semi-synthetic analogs that are modified at the C6 and C4 sites. The two best analogs were two orders of magnitude more potent than BlaS against Plasmodium falciparum drug-sensitive and -resistant lines while displaying low cytotoxicity towards mammalian cells. These analogs exhibited improved kinetics of inhibition of protein synthesis in cultured parasites and blocked the development of asexual stages expressing the plasmodial surface anion channel, a transporter required for nutrient acquisition and BlaS uptake. They also exhibited a dramatically improved speed of killing over BlaS. Molecular docking analysis revealed that these analogs are able to form more interactions with the P. falciparum ribosomal peptidyl transferase center than is BlaS, which is consistent with their increased potency. Together, these studies demonstrate the feasibility of generating BlaS analogs with potent anti-malarial activity and provide a roadmap for further development.

Gonorrhea is the second most common bacterial sexually transmitted infection and affects about 80 million people worldwide annually. The causative agent, Neisseria gonorrhoeae, has become resistant to almost every antibiotic used for its treatment. There is no licensed vaccine against gonorrhea. Therefore, there is an urgent need to develop novel prevention and treatment strategies to curb the spread of gonorrhea. The gonococcus has evolved several mechanisms to evade complement, a key arm of immune defenses against this pathogen, including binding of the human complement inhibitors Factor H (FH) and C4b-binding protein (C4BP). We previously showed that chimeric molecules fusing the gonococcal binding domains of FH and C4BP to IgG Fc and IgM Fc, respectively, mediate complement-dependent killing of gonococci in vitro and attenuate gonococcal colonization of mouse vaginas when administered topically. Here, we fused C4BP domains 1 and 2, which contain the gonococcal binding region, to IgG Fc bearing the IgM tail-piece to facilitate Fc hexamerization. This molecule, called C4BP-Hexa IgG Fc, showed [~]650-fold greater complement-dependent bactericidal activity on a molar basis than monomeric C4BP-IgG1 Fc. C4BP-Hexa IgG Fc enhanced association with and uptake by human neutrophils in a complement-independent manner. Despite off-target complement activation in solution, C4BP-Hexa IgG Fc reduced both the duration and the bacterial burden of gonococcal vaginal colonization in human FH and C4BP transgenic mice when administered intravaginally daily. In conclusion, we show proof-of-concept of the efficacy of a hexameric C4BP IgG Fc fusion molecule against N. gonorrhoeae, which could aid in the fight against this multidrug-resistant pathogen.

Intravital microscopy enables direct visualization of dynamic cellular processes within intact tissues, but its application to Mycobacterium tuberculosis (Mtb) has been limited by Biosafety Level 3 (BSL-3) containment requirements and the technical challenges of stabilizing the lung for high-resolution imaging. Here, we present a protocol that combines the thoracic Window for High-Resolution Imaging of the murine Lung (WHRIL) with a genetically defined, triple-auxotrophic Mtb strain (mc27902) approved for use under BSL-2 conditions. We describe the construction of a tdTomato-expressing derivative (mc28471) preparation of bacteria for intravenous infection and intravital imaging in reporter mice. This system enables visualization of rapid bacterial entry into the pulmonary vasculature, subsequent aggregation, and vascular occlusion, dissemination into the lung parenchyma, and macrophage uptake over three days post-infection. This protocol provides the first practical platform for real-time intravital imaging of mycobacteria in the lung and establishes a foundation for mechanistic studies of bacterial physiology, host recognition, and immune-mediated clearance using safe Mtb surrogates. SummaryThis protocol describes a biosafety level 2 (BSL-2)-compatible intravital imaging platform for visualizing Mycobacterium tuberculosis (Mtb) in the intact murine lung at single cell resolution. By combining the Window for High-Resolution Imaging of the murine Lung (WHRIL) with a fluorescently labeled, genetically defined triple auxotrophic Mtb strain (mc27902), this approach overcomes long-standing biosafety and technical barriers that have prevented real-time imaging of mycobacterial infection in vivo. The method enables direct visualization of early bacterial localization, aggregation, vascular interactions, and macrophage uptake during the initial hours to days following infection, providing a practical foundation for mechanistic studies of host-pathogen interactions under safe experimental conditions.

The rise of MDR Klebsiella pneumoniae and its resistance to the last-resort antibiotic colistin poses a significant threat to global healthcare. While genomic studies have identified several resistance mutations, the transient proteomic shifts that occur during the initial exposure of sensitive strains to lethal antibiotic doses remain poorly characterised. In this study, we employed a label-free quantitative proteomics approach to investigate the protein expression profile of K. pneumoniae strain ATCC 13883 treated with colistin at its MIC. Membrane proteins were extracted at critical growth stages, and differentially abundant proteins (DAPs) were analysed using Gene Ontology and KEGG pathway enrichment analysis. Our proteomic analysis identified 718 DAPs (339 upregulated and 379 downregulated). The cellular response was characterised primarily by outer membrane remodelling and a significant upregulation of the capsule-associated kinase Wzc and the ArnBCADTEF operon, which facilitates lipid A modification with L-Ara4N moiety. Paradoxically, while RND-family efflux pumps (AcrAB) were significantly induced, the global activator RamA and major porins (OmpA, OmpX, LamB) were downregulated, possibly to minimise antibiotic entry. KEGG pathway enrichment analysis further revealed a synchronised metabolic shift, characterised by an intensified TCA cycle flux to fuel high-energy resistance processes despite a general slowdown in carbohydrate metabolism. Our findings demonstrate that K. pneumoniae responds to colistin stress through a rapid, multifaceted proteomic reorganisation involving charge neutralisation, structural reinforcement of the cell envelope, and metabolic re-routing. These results provide a molecular blueprint of the early adaptive response, identifying several proteins as potential therapeutic targets.

In vitro methods to characterize drug combinations typically involve phenotypic screenings using checkerboard assays (CBA) or, more recently, DiaMOND. Such approaches rely on the Fractional Inhibitory Concentration Index (FICI), a fixed-time measurement of growth inhibition that, nonetheless, necessitates secondary validation by time-kill assays (TKA). Longitudinal time-kinetics of bacterial killing are considered the gold standard in vitro proxy for antimicrobial activity, but they required increased assay complexity, particularly against the slow growing Mycobacterium tuberculosis. Here, we developed a new methodology named OPTIKA (Optimized Time Kill Assays) that enhances the capacity of traditional TKA by over 1000-fold. This allows for easy and dynamic examination of n-way drug interactions by simultaneously monitoring bactericidal and sterilizing capacities in a longitudinal manner. We then replicated previous DiaMOND studies and performed comparisons using CBA and OPTIKA methodologies. We demonstrate that selection of the efficacy parameters (either routed on bacteriostatic, bactericidal or sterilizing properties) affects the interpretation of in vitro drug interactions and, consequently, its potential translational value. The increased assay throughput provided by OPTIKA offers a novel framework for developing tuberculosis treatment regimens. TeaserOPTIKA is a new methodology that increases time-kill assay performance against Mycobacterium tuberculosis by over 1,000-fold

Multidrug efflux pumps transport antibiotics across the cellular membrane resulting in resistance conferred to the host organism. Efflux pump inhibitors (EPIs) potentiate the efficacy of antibiotics by blocking drug efflux and hold promise as adjuvant therapeutics in the fight against multidrug resistant pathogenic bacteria. A hurdle in the field has been the lack of selectivity of small molecule EPIs which often display off-target toxicity due to non-specific binding. To tackle this specificity challenge, we aimed to maximize an inhibitors binding surface area to efflux pumps by designing miniprotein EPIs using computational protein design and an E. coli co-expression assay to screen inhibition in cells. We used S. aureus NorA as a model efflux transporter since it confers drug resistance to fluoroquinolones, puromycin, and other cytotoxic compounds. Starting from a focused miniprotein library of only 86 members, we identified inhibitors in the screen that blocked NorA transport under active efflux conditions in vitro. Our most promising inhibitor I-23 was validated by solving a cryo-EM structure of the miniprotein in complex with NorA, which stabilized the transporter in the outward-open conformation. I-23 has a ferredoxin-like fold with one of its {beta}-hairpins inserted into the substrate binding pocket of NorA and other parts of the globular fold occupying the shallow pocket and making extensive intermolecular contacts with NorA. An arginine residue on the tip of the hairpin loop was positioned near an anionic patch required for NorA antibiotic efflux. The identified structural motifs in this work could be employed to explore the molecular properties of peptidoglycan penetration; full realization of the therapeutic potential of the designed miniprotein inhibitors will require determining the principles for facilitating passage of [~]7 to 8 kDa miniproteins across the peptidoglycan bacterial cell wall.

Toxoplasma gondii is a protozoan parasite capable of infecting most warm-blooded animals, including humans, and can cause severe disease in immunocompromised individuals and the developing fetus. Current treatments for toxoplasmosis are effective only against the acute stage of infection and have limited or no activity against the latent bradyzoite stage found within tissue cysts. The mitochondrion of T. gondii is a validated drug target, and the clinically used drug atovaquone acts by inhibiting the mitochondrial electron transport chain (ETC) at the coenzyme Q:cytochrome c oxidoreductase (bc1 complex). In this study, we evaluate two legacy 4(1H)-quinolones: ICI 56,780 and WR 243246, previously shown to inhibit the Plasmodium falciparum bc1 complex, for their efficacy against T. gondii. Both compounds inhibit tachyzoite growth with low-nanomolar EC values and disrupt parasite mitochondrial function by blocking cytochrome c reduction and collapsing the mitochondrial membrane potential. Notably, ICI 56,780 protects mice from lethal infection with type I RH tachyzoites. Importantly, ICI 56,780 also exhibits potent activity against chronic-stage parasites, reducing cyst size and bradyzoite viability in vitro and showing low-nanomolar EC values against in vivo-derived bradyzoites. In mice chronically infected with T. gondii, treatment with ICI 56,780 significantly decreases brain cyst burden. Although these 4(1H)-quinolones display some pharmacokinetic limitations, our findings highlight their potential as promising chemotypes active against both acute and chronic stages of T. gondii and provide a framework for future medicinal chemistry efforts to improve drug-like properties while preserving or enhancing anti-bradyzoite activity.

Pertussis pathogenesis is the result of multiple virulence factors. In addition to the secretory proteins of Bordetella pertussis, surface molecules such as adhesins and endotoxin play a role in the pathogenesis of this disease. There are conflicting reports on the existence and nature of the Bordetella capsular polysaccharides or exoglycans. The data concerning the glycome of Bordetellae is incomplete. This conclusion is primarily derived from genomic data, with only limited indications regarding the actual structures. In this study, we present novel data on the exoglycan produced by all strains and species of the investigated bacteria from the genus Bordetella, including Bordetella pertussis, Bordetella parapertussis, Bordetella bronchiseptica, and Bordetella holmesii. This is the first time this type of data has been provided. The exoglycan was consistently recovered from the chemically defined culture media of various Bordetellae species and strains. The compound was identified by nuclear magnetic resonance (NMR) as a free hexasaccharide released into the medium and thus received its name, Bordetella oligosaccharide (BOS). The biosynthetic origin of the BOS was confirmed by NMR combined with metabolic labeling in culture, using 13C,15N-L-glutamate as a primary carbon source. The identification of BOS has the potential to enhance our comprehension of the complete array of virulence factors contributing to the pathogenesis of Bordetella pertussis, particularly in regard to their relations with other Bordetella species. In the field of vaccine design, glycan structures are typically of utmost importance; however, they were hardly ever considered in the case of pertussis.

Pseudomonas aeruginosa is an adaptable organism, frequently found in chronic infections, and for which antimicrobial resistance is a growing concern. Therefore, there is an urgent need for alternative therapeutic strategies. Cationic antimicrobial peptides (AMPs) offer potent bactericidal activity but suffer from limited selectivity and potential host toxicity. To enhance species-specific targeting, we designed two prodrug variants of the AMP D-Bac8CLeu2,5 - EEEE-D-Bac8CLeu2,5 and ELEG-D-Bac8CLeu2,5 -- engineered for activation by the P. aeruginosa extracellular aminopeptidase PaAP. While both prodrug motifs effectively neutralized the positive charge of D-Bac8CLeu2,5 and prevented DNA-peptide complex formation, EEEE-D-Bac8CLeu2,5 showed negligible antimicrobial activity due to slow and incomplete activation. In contrast, ELEG-D-Bac8CLeu2,5 underwent rapid PaAP-mediated activation, restoring bactericidal activity in planktonic cultures and biofilms. PaAP contributed significantly to complete prodrug activation, particularly within biofilms, where the accumulation of partially activated intermediates correlated with biphasic killing kinetics. The prodrug showed reduced activity against other ESKAPEE pathogens, demonstrating selective activation by P. aeruginosa. Experiments selecting resistant bacteria revealed distinct mutations in lipopolysaccharide biosynthesis pathways for D-Bac8CLeu2,5 and the prodrug, with limited cross-resistance. These findings establish aminopeptidase-activated AMP prodrugs as a promising approach for species-selective antimicrobial therapy and highlight the feasibility of exploiting bacterial enzymes for controlled antimicrobial peptide activation. Table of contents graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=99 SRC="FIGDIR/small/715093v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@4a5505org.highwire.dtl.DTLVardef@13e578org.highwire.dtl.DTLVardef@3e3080org.highwire.dtl.DTLVardef@e24266_HPS_FORMAT_FIGEXP M_FIG C_FIG

Pantothenamides (PanAms) comprise a promising class of antimalarial compounds that kill asexual blood-stage Plasmodium falciparum parasites and block transmission. Intriguingly, the most advanced PanAm in drug development, MMV693183, is approximately 100 times more potent against female gametocytes than males. We hypothesized that this specificity is explained by a difference in PanAm uptake, which we studied using a PanAm-based photoaffinity labelling (PAL) probe. We successfully synthesized a probe that competed with MMV693183 in drug sensitivity assays, while the probe did not display high potency by itself. We observed no significant difference in median fluorophore-labelled probe signal intensity between male and female gametocytes, although there might be a difference in subcellular localization of the probe between the sexes. By combining PAL with affinity purification and mass spectrometry, we were not able to identify novel candidate PanAm transporters. We conclude that PAL provides evidence that differences in PanAm uptake do not underly differences in PanAm sensitivity between the gametocyte sexes.

The emergence of antimicrobial resistance (AMR) has driven the search for alternative therapeutic strategies, including antivirulence approaches targeting bacterial quorum sensing (QS). Azelaic acid (AzA), a naturally occurring dicarboxylic acid with known antimicrobial properties, has not previously been characterized as a QS inhibitor in Gram-negative pathogens. This study evaluated the dual antimicrobial and antivirulence activity of AzA against reference strains and clinical isolates of Pseudomonas aeruginosa, Enterobacteriaceae, and Staphylococcus aureus through in vitro assays and molecular docking analyses. Minimum inhibitory concentration (MIC) values ranged from 250 to 1000 {micro}g/mL, with lower MICs observed in clinical isolates of E. coli and S. aureus. Subinhibitory concentrations (250, 500 and 750 {micro}g/mL) were used to assess QS-regulated virulence factors in P. aeruginosa, including pyocyanin, elastase, alginate, and protease production. AzA exhibited a significant, dose-dependent inhibition of all evaluated virulence factors across both reference and multidrug-resistant (MDR) and pan-drug-resistant (PDR) clinical strains (p < 0.001), achieving inhibition levels exceeding 90% in several cases, particularly for protease activity. Molecular docking analyses revealed that AzA interacts with key QS-related proteins (LasI, LasR, PqsD, and PqsR), showing moderate binding affinities (-5.3 to -6.5 kcal/mol) and stable interactions within conserved ligand-binding domains. These findings suggest a multitarget modulatory mechanism affecting interconnected QS pathways. Overall, this study demonstrates, for the first time, that AzA acts as a quorum sensing inhibitor in P. aeruginosa, attenuating virulence without directly affecting bacterial growth, highlighting its potential as a promising antivirulence therapeutic strategy.

The SARS CoV 2 accessory protein Orf9b is in a complex monomer-dimer equilibrium that influences its interactions with the host mitochondrial receptor Tom70. This interaction is critical for viral suppression of a Type-1 interferon response during infection. Modulating this equilibrium with a small molecule, either by stabilizing the Orf9b dimer or blocking its interaction with Tom70, represents a promising strategy for restoring interferon signaling and the antiviral response. To build tool molecules that could test this concept, we performed two screens: a crystallographic fragment screen against the Orf9b homodimer and a high-throughput fluorescence polarization screen for competitors of an Orf9b-derived peptide binding to Tom70. Fragment screening revealed two binding sites with potential to be developed into an inhibitor: one located at the peripheral dimer interface and the other just outside the lipid-binding channel that defines the central dimer interface. Functionalization of the fragments outside of the lipid-binding channel with hydrophobic moieties stabilized the Orf9b dimer thereby indirectly inhibiting association with Tom70. In parallel, the high throughput screen for competitive inhibitors of the Tom70:Orf9b interaction discovered a separate series of molecules. These molecules display dynamic structure activity relationship (SAR) and could be improved in the future to modulate the interaction between Tom70 and potentially a wide range of substrates. Collectively, these results demonstrate the feasibility of two distinct strategies to manipulate the Orf9b-Tom70 equilibrium, which is critical to the host response to SARS CoV 2 infection.

Despite multiple treatment strategies and extensive research on resistance mechanisms, tuberculosis (TB) remains a major global health threat, largely because of the rise of multidrug-resistant (MDR) and extensively drug-resistant (XDR) TB. Among various mechanisms complicating the situation, active antibiotic export via efflux pumps is particularly significant, yet largely unexplored. Mycobacterium sp. encodes numerous transporters, many of which are overexpressed in clinical isolates or under drug stress. Here, we examined the possible role of Rv0783c, a putative transporter that is reportedly overexpressed in drug-stressed conditions. Rv0783c conferred resistance to multiple structurally diverse antibiotics, fluoroquinolones and anti-TB drugs in the heterologous hosts, namely, Escherichia coli and Mycobacterium smegmatis. Reduced drug accumulation and active efflux of ethidium bromide (EtBr) confirmed its transport activity, which in turn gets nullified upon using the proton-motive force blocker, CCCP. On the other hand, its expression enhanced biofilm formation, linking antibiotic resistance to persistence-associated phenotype. Furthermore, site-directed mutagenesis confirmed the presence of crucial interacting residues with antibiotics that were identified by in silico analysis. Overall, we demonstrate the role of Rv0783c in the extrusion of first and second-line anti-TB drugs and enhancing biofilm formation.

Multidrug resistant (MDR) bacterial wound infections are an increasing clinical challenge and require alternatives to conventional antibiotics. Although antimicrobial proteins offer promise, their therapeutic use is limited by poor stability, proteolytic degradation, reduced activity under physiological conditions, and potential toxicity. This work reports pH-sensitive lipid nanocarriers composed of granulysin (GNLY) and oleic acid (OA) for antimicrobial delivery to infected tissues. At neutral pH, GNLY is retained within OA-based nanocarriers and protected from proteolytic degradation. At pH 5.0, such as in infected wounds, the carriers undergo structural reorganization and release GNLY, restoring antimicrobial activity. OAGNLY (32 {micro}g/mL) achieved >3-log reductions in Staphylococcus aureus and Escherichia coli within 1 hour, and up to 4-log reductions in Pseudomonas aeruginosa and Acinetobacter baumannii, at physiological salt concentrations where free GNLY was largely inactive. Minimum inhibitory concentrations were 16 {micro}g/mL for MRSA and 32 {micro}g/mL for colistin-resistant E. coli. Ultrastructural analysis using transmission electron microscopy revealed disruptions of bacterial membranes and intracellular structures following OAGNLY treatment. In a murine surgical wound infection model, topical application of OAGNLY for 4 hours reduced bacterial burden by >5 logs and significantly decreased inflammation, as confirmed by histological analysis. In parallel, OAGNLY demonstrated minimal cytotoxicity to mammalian cells at active concentrations. These findings identify OAGNLY nanocarriers as a promising platform for pH-responsive delivery of GNLY and highlight their potential application for treating MDR skin and soft tissue infections..

The development of broadly protective and dose-sparing influenza vaccines remains a critical challenge, particularly for zoonotic H5N1 strains with pandemic potential. This study evaluates BECC470s, a synthetic TLR4 adjuvant, for its ability to enhance the immunogenicity and protective efficacy of recombinant H5 hemagglutinin (rHA) vaccination in murine models. BECC470s-adjuvanted rHA elicited robust IgG1/IgG2a antibody responses and complete survival following homologous 2004 H5N1 challenge in a prime-boost model. Although BECC470s broadened antibody binding to both variable HA head and conserved stalk domains by ELISA, functional neutralizing antibody responses were restricted to the matched 2004 H5N1 isolate, with no detectable neutralization of H5N1 viruses isolated in 2022 or 2024. These data indicate that BECC470s enhances the magnitude and apparent breadth of binding antibody responses while maintaining strain-specific neutralizing activity, supporting its potential as an adjuvant for next-generation influenza vaccines while underscoring the need for further optimization to achieve true cross-neutralizing protection.

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are key components of combination antiretroviral therapy (ART) for the treatment of human immunodeficiency virus type 1 (HIV-1) infection, binding an allosteric pocket of reverse transcriptase (RT) and inhibiting viral replication. Although second-generation NNRTIs have improved potency and resistance profiles compared to first-generation NNRTIs, the continued emergence of resistant viral strains and the need for long-acting therapeutic options underscore the importance of developing next-generation compounds. Depulfavirine (VM1500A) is a potent NNRTI being developed as a long-acting formulation. Its prodrug, elsulfavirine (ESV), is approved for HIV-1 treatment in Eurasian countries as a once-daily oral regimen and has demonstrated favorable antiviral efficacy, pharmacokinetics, and tolerability in clinical studies. Here, we report the 2.4 [A] crystal structure of HIV-1 RT in complex with depulfavirine, revealing an extended binding conformation within the NNRTI pocket that reaches from the back of the binding pocket to the entrance. These interactions may shed light on mechanisms of resistance to the F227C mutation, with and without V106 substitution, and Y188L. Notably, depulfavirine maintains potent inhibition of common NNRTI-resistant RT variants, including K103N and Y181C. Combination studies of ESV with antivirals from diverse inhibitor categories demonstrated additive or near-synergistic activity with islatravir (ISL), cabotegravir (CAB), lenacapavir (LEN), and tenofovir (TDF). These findings highlight the broad resistance profile and potential of the depulfavirine combination.