ACS Infectious Diseases最新文献

Bacterial resistance, accelerated by the misuse of antibiotics, remains a critical concern for public health, promoting an ongoing exploration for cost-effective and safe antibacterial agents. Recently, there has been significant focus on various nanomaterials for the development of alternative antibiotics. Among these, molybdenum disulfide (MoS₂) has gained attention due to its unique chemical, physical, and electronic properties, as well as its semiconducting nature, biocompatibility, and colloidal stability, positioning it as a promising candidate for biomedical research. The impact of the shape and size of MoS₂ nanomaterials on the antibacterial activity remains largely unexplored. In this study, we investigated the effect of the shape and size of MoS₂ nanomaterials, such as quantum dots, nanoflowers, and nanosheets, on antimicrobial and anti-biofilm activity. As we had established earlier, functionalization with positively charged thiol ligands can enhance colloidal stability, biocompatibility, and antibacterial efficacy; we functionalized all targeted nanomaterials. Our results revealed that functionalized MoS₂ quantum dots (F-MQDs) exhibited superior activity compared to functionalized MoS₂ nanoflowers (F-MNFs) and functionalized MoS₂ nanosheets (F-MNSs) against Staphylococcus aureus (SA), both drug-resistant (methicillin) and nonresistant strains. We observed very low minimum inhibitory concentration (MIC, 30 ng/mL) for F-MQDs. The observed trend in antibacterial efficacy was as follows: F-MQDs > F-MNFs ≥ F-MNSs. We explored the relevant mechanism related to the antibacterial activity where the balance between membrane depolarization and internalization plays the determining role. Furthermore, F-MQDs show enhanced anti-biofilm activity compared to F-MNFs and F-MNSs against mature MRSA biofilms. Due to the superior antibacterial and anti-biofilm activity of F-MQDs, we extended their application to wound healing. This study will help us to develop other appropriate surface modified nanomaterials for antibacterial and anti-biofilm activity for further applications such as antibacterial coatings, water disinfection, and wound healing.

Persiathiacin A is a novel thiopeptide antibiotic produced by Actinokineospora species UTMC 2448. It has potent activity against methicillin-resistant Staphylococcus aureus (MRSA) and Mycobacterium tuberculosis. Thiopeptides, including persiathiacin A, exhibit antibacterial activity by inhibiting protein synthesis. In this study, we characterize the mechanism of action of persiathiacin A and investigate how resistance to this antibiotic can emerge. In vitro assays revealed that persiathiacin A inhibits translation elongation, leading to ribosome stalling. Genetic analysis of resistant Bacillus subtilis mutants identified mutations primarily in the rplK gene encoding ribosomal protein L11, which is the binding site for other 26-membered macrocycle-containing thiopeptides. The resistant mutants showed growth impairment and an increased lag time, even in the absence of persiathiacin. Comparative proteomic analysis of a resistant mutant versus the parental strain revealed multiple changes, indicative of negative effects on protein synthesis. Thus, although persiathiacin-resistant mutants can arise readily by the loss of L11 function, it is likely that such mutants would be severely compromised in pathogenesis. Furthermore, bioinformatics analysis identified differences in the key amino acids within the thiopeptide-binding region of L11 in the persiathiacin producer. These probably prevent the antibiotic from associating with its target, providing a mechanism for self-resistance.

Candida (Nakaseomyces) glabrata, an opportunistic human fungal pathogen, causes mucosal and deep-seated infections in immunocompromised individuals. Recently designated as a high-priority fungal pathogen by the World Health Organization (WHO), C. glabrata exhibits low inherent susceptibility to azole antifungals. In addition, about 10% clinical isolates of C. glabrata display co-resistance to both azole and echinocandin drugs. Molecular mechanisms of antifungal resistance and virulence in C. glabrata are currently being delineated in-depth. This Review provides an overview of the epidemiology, biology, drug resistance, tools and host model systems for C. glabrata. Additionally, we discuss the immune evasion strategies that aid C. glabrata in establishing infections in the host. Overall, this Review aims to contribute to ongoing efforts to raise awareness of human pathogenic fungi, the growing threat of antifungal drug resistance and the unmet need for novel antifungal therapies, with an ultimate goal of improving clinical outcomes of affected individuals.

Streptococcus oligofermentans, a Gram-positive bacterium found in the oral microbiome, shows promise as an oral probiotic for preventing dental caries. It exhibits a reverse correlation with Streptococcus mutans, a key caries-causing pathogen, likely due to its production of hydrogen peroxide, a process mediated by quorum sensing (QS). In this work, we set out to develop novel lactam-based cyclic analogues of the competence stimulating peptide (CSP) signal utilized by S. oligofermentans for QS activation. To this end, we first conducted a ring position scan, where we determined the best positions within the CSP sequence to use for macrolactamization. We then conducted systematic ring size and bridge position scans to fine-tune the cyclic peptide conformation and identified a cyclic analogue, CSP-cyc(K2E2), with enhanced biological activity, 7-fold more active than the native CSP signal. This analogue also exhibited improved stability toward enzymatic degradation, demonstrating this analogue's potential utility as a chemical probe to study interspecies interactions between oral microbes and as a potential therapeutic agent. Overall, our lead cyclic analogue could be applied to augment the biotherapeutic potential of S. oligofermentans against S. mutans infections.

Infective endocarditis (IE) represents a significant concern among hospital-acquired infections, frequently caused by the Gram-positive bacterium Staphylococcus aureus. Nuclear imaging is emerging as a noninvasive and precise diagnostic tool. However, the gold standard radiotracer [¹⁸F]-FDG cannot distinguish between infection and inflammation, resulting in false positives. Based on the presence of collagen-binding proteins in the cell wall of S. aureus, we propose the radiolabeling of collagen for its evaluation in IE animal models by single-photon emission computed tomography (SPECT) imaging. We radiolabeled rat tail collagen I using DTPA chelator and [^99mTc]NaTcO₄. Selectivity was evaluated in vitro using 3 Gram-positive bacteria, 1 Gram-negative bacteria and 1 yeast. In vivo SPECT/computed tomography (CT) imaging was conducted on 8 SD rat models of IE and 8 sterile sham model as controls. Ex vivo biodistribution and autoradiography were performed following imaging. Diagnosis of IE was confirmed through microbiological studies and H&E histopathology. [^99mTc]-DTPA-Collagen was synthesized successfully with a yield of 42.86 ± 6.35%, a purity of 95.84 ± 1.85% and a stability higher than 90% after 50 h postincubation. In vitro uptake demonstrated the selectivity for Gram-positive bacteria (63.85 ± 15.15%). Ex vivo analysis confirmed hepato-splenic excretion. In vivo SPECT/CT imaging revealed highly localized uptake within the aortic valve with a sensitivity of 62.5% and specificity of 87.5%. We successfully synthesized and characterized a new SPECT radiotracer based on [^99mTc]Tc-radiolabeled collagen. In vitro studies demonstrated the selectivity of the radiotracer for Gram-positive bacteria. In vivo SPECT/CT-based assessment in an IE model confirmed the potential of this approach to detect active IE.

Orthopedic implant infections (OIIs) present diagnostic and therapeutic challenges, owing to the lack of methods to distinguish between active infection and sterile inflammation. To address this unmet need, d-amino-acid-based radiotracers with unique metabolic profiles in microorganisms have emerged as a novel class of infection-specific imaging agents. Given the pivotal role of d-glutamine in bacterial biofilm formation and virulence, herein, we explored the potential of positron emission tomography (PET) imaging with d-[5-¹¹C]-Glutamine (d-[5-¹¹C]-Gln) for early detection and treatment monitoring of OIIs. In vitro studies confirmed an active uptake of d-[5-¹¹C]-Gln by Staphylococcus aureus (S. aureus) biofilm commonly associated with OIIs. In vivo evaluations included PET imaging comparisons with d-[5-¹¹C]-Gln vs l-[5-¹¹C]-Gln or 2-deoxy-2-[¹⁸F]-fluoroglucose ([¹⁸F]-FDG) in a rat OII model with tibial implantation of sterile or S. aureus-colonized stainless-steel screws before and after treatment. These studies demonstrated that the uptake of d-[5-¹¹C]-Gln was significantly higher in the infected screws than that in sterile screws (∼3.4-fold, p = 0.008), which displayed significantly higher infection-to-background muscle uptake ratios (∼2-fold, p = 0.011) with d-[5-¹¹C]-Gln as compared to l-[5-¹¹C]-Gln. Following a 3 week vancomycin treatment, imaging with d-[5-¹¹C]-Gln showed a significant reduction in uptake at the infected sites (∼3-fold, p = 0.0008). Further regression analyses revealed a superior correlation of residual infection-associated radiotracer uptake with the postimaging ex vivo bacterial counts for d-[5-¹¹C]-Gln (k = 0.473, R² = 0.796) vs [¹⁸F]-FDG (k = 0.212, R² = 0.434), suggesting that d-[5-¹¹C]-Gln PET had higher sensitivity for detecting residual bacterial burden than [¹⁸F]-FDG PET. Our results demonstrate the translational potential of d-[5-¹¹C]-Gln PET imaging for noninvasive detection and treatment monitoring of OIIs.

The discovery of antimicrobials was an inflection point in human existence since it contributed enormously to the extension of the human lifespan. Among others, the invention of Enmetazobactam marks a significant milestone in the field of antimicrobial development, especially for India. It is a novel beta-lactamase inhibitor invented by scientists at Orchid Pharma in Chennai, India, and has garnered international attention for its potential to address antimicrobial resistance. It became the first new chemical entity invented in India, clinically developed by Allecra Therapeutics GmbH, to be approved by the U.S. Food & Drug Administration, with additional approvals from the European Medical Agency, the U.K.'s Medicine & Healthcare Products Regulatory Agency, and the Drug Controller General of India.

The calcium-dependent antibiotics (CDAs) are a group of seven closely related membrane-active cyclic lipopeptide antibiotics (cLPAs) first isolated in the early 1980s from the fermentation broth of Streptomyces coelicolor. Their target was unknown, and the mechanism of action is uncertain. Herein, we report new routes for the synthesis of CDA4b and its analogues, explore the structure-activity relationships at its lipid tail and at positions 3, 9, and 11, and determine the CDAs' lipid target. A CDA4b analogue in which the epoxide group in CDA's 6-carbon lipid was replaced with a cyclopropyl group was 4-fold more active than CDA4b which suggests that the epoxide group is not acting as an electrophile to form a covalent bond with CDA4b's target. The activity of this cyclopropyl analogue was significantly increased by extending the length of the lipid to 10 carbons. Studies with analogues in which d-HOAsn9 is replaced with d-Asn9 or d-Ser9 reveal that the hydroxy group of the d-HOAsn9 residue is not crucial for CDAs' activity, while the amide moiety is important for activity. The l-Trp residue at position 11 could be replaced with l-kynurenine (l-Kyn) without significant loss of activity, while replacing the d-Trp residue at position 3 with d-Kyn resulted in a significant loss of activity. MIC values determined in the presence and absence of exogenous phospholipids and fluorescence spectroscopy studies using natural CDAs and CDA4b analogues containing Kyn and model membranes revealed that the CDAs' primary lipid target is cardiolipin, a target that is unique among the broader class of known calcium-dependent antibiotics.

African trypanosomiasis is a widespread disease of human and veterinary importance caused by various Trypanosoma spp. with a globally devastating impact and a need for novel treatment options. We here provide a comprehensive preclinical evaluation of nucleoside analogues, 6-thioether-modified tubercidins, with curative activity against African trypanosomiasis. Promising hits were identified following in vitro screening against the most relevant trypanosome species. Selected hit compounds were extensively tested for in vitro metabolic stability, potency in in vivo mouse models for the various species, genotoxicity in an in vitro testing battery, and mode of action studies (i.e., genome-wide RNA interference library screening and metabolomics). Among the nucleoside analogues, analogue 3 was curative in mouse models with no indication of genotoxicity and a low ecotoxicological footprint. Mode-of-action studies revealed that P1-type nucleoside transporters and adenosine kinase are involved in the uptake and activation, respectively. Analogue 3 represents a potent, advanced lead fitting the preferred target product profile for a broad-spectrum trypanocide regardless of the causative species.

Falciparum malaria relies extensively on cell-to-cell communication, and earlier research on the function of exosomal proteins derived from infected red blood cells (iRBCs) has been classified into numerous important roles. In this study, the exosomes were derived from Pf3D7-iRBCs cultured in vitro during synchronized trophozoite stages. The isolated exosomes were assessed using NTA, FE-SEM, and flow cytometry. Our study reported heterogeneous populations of exosomes during the infection. Additionally, label-free quantification based on LC/MS-MS for protein profiling revealed the presence of both parasitic and host (RBC) proteins; out of a total of 124 proteins detected, 20 Pf3D7 proteins and 80 RBC proteins were identified. Exosomal RBC protein expression is different in cRBCs-Exo and iRBCs-Exo, which shows how the parasite and RBCs interact with each other. Functional classification reported that the majority of these Pf3D7 proteins are uncharacterized with unknown functions, few of which are involved in biological processes such as regulation of complement activation, response to external stimuli, immune system-mediated signaling pathway, protein processing, etc. Hence, studying these exosomal proteins and comparing them to previous research has helped us understand how exosomes help cells to communicate in malaria. It may also reveal new potential biomarkers for diagnostic methods or therapies for malaria.