Frontiers in Microbiology最新文献

Klebsiella pneumoniae pneumonia is marked by an excessive inflammatory response that drives lung injury. The initial stages of infection and the mechanisms driving hyper-inflammation at the airway epithelial barrier are not fully defined. The alarmins S100A8/A9 are potent inflammatory mediators, and studies have indicated their importance in the host response to K. pneumoniae. Here, we show that infection with live K. pneumoniae directly induces the transcription and secretion of the S100A8/A9 heterodimer in a primary human bronchial epithelial (HBE) cell model. Furthermore, the infection sensitizes epithelial cells by upregulating the expression of Toll-like receptor 4, a key receptor that mediates S100A8/A9 signaling. We also established that HBE cells are highly responsive to extracellular S100A8/A9, which stimulates pro-inflammatory cytokine production. Critically, silencing of endogenous S100A9 expression in HBE cells significantly attenuated NF-κB activation and the overall cytokine response to bacterial infection, providing direct evidence for an epithelium-intrinsic autocrine amplification loop. Functionally, disruption of this loop markedly reduced the ability of epithelial cell supernatants to induce neutrophil chemotaxis. These findings reveal a novel autocrine mechanism that positions the airway epithelium not just as a responder, but as an active initiator and amplifier of local inflammation during early K. pneumoniae infection.

Introduction: The Asian water plantain, Alisma orientale (Sam.) Juzep, is a flowering hydrophytic plant that grows in marshes. In traditional Chinese medicine, the rhizome of A. orientale is highly valued for its medicinal properties. Endophytic microbes modulate plant growth and the biosynthesis of secondary metabolites, however little is known concerning these effects in A. orientale.

Methods: Here, high-throughput sequencing and culturing methods were utilized to investigate the endophytic fungal diversity in the rhizomes, flowers, roots and leaves of A. orientale. In vitro assays were employed to screen for strains exhibiting high growth-promoting abilities based on phosphate solubilization, siderophore production, oxidative stress resistance, and indole-3-acetic acid (IAA) production. Transcriptomics and whole genome sequencing were employed to investigate the underlying molecular mechanisms.

Results: These data revealed that the Ascomycota and Basidiomycota were dominant phyla in all parts, with significant variation in fungal community composition observed at the genus level, as reflected in alpha and beta diversity indices. A total of 19 different endophytic fungal strains were isolated via culturing methods from the four different parts of A. orientale. In vitro assays resulted in the identification of four isolates subsequently used for co-culturing with sterile A. orientale to monitor plant-growth and terpenoid production. These latter results identified one promising strain, RT1, characterized as Pseudothielavia terricola. Isolate RT1 enhanced plant growth by 100-121% with respect to root length and plant height as compared to controls. After 21 days of treatment with strain RT1, the contents of the triterpenoids alisols B-23, C-23, and B were 4.5-5.5 times higher than those of the controls. Transcriptomics revealed enhanced expression of key enzymes involved in plant growth and bioactive compound accumulation, including 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), mevalonate diphosphate decarboxylase (MVD), farnesyl diphosphate synthase (FPPS), 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), 1-deoxy-D-xylulose-5-phosphate synthase (DXS), farnesyl-diphosphate farnesyltransferase (FDFT1), and squalene monooxygenase (SQLE) during RT1 interaction. Whole genome sequencing of P. terricola revealed the presence of several gene clusters involved in tryptophan synthesis.

Discussion: This study establishes endophytic fungal enhancement of A. orientale growth and bioactive compound accumulation, thereby increasing crop value and utility.

[This corrects the article DOI: 10.3389/fmicb.2025.1714857.].

Introduction: Human noroviruses (HuNoVs) are genetically diverse RNA viruses that cause acute gastroenteritis, with genogroup II (GII) accounting for over 90% of global infections. Glycans, particularly histo-blood group antigens (HBGAs), have been identified as attachment factors or receptors for HuNoVs infection. However, the glycan-binding receptors of the later-identified GII genotypes GII.23/24/25 remain elusive.

Methods: We used saliva- and glycan-based ELISA assays to identify the binding spectra of GII.23/24/25 strains. We also solved the crystal structures of their P domains, including the GII.25 P domain in complex with the H disaccharide. Single-point mutagenesis was performed to identify key residues involved in glycan binding.

Results: The P domains of GII.24 and GII.25 can recognize multiple types of saliva samples, including both A/B/O secretor and nonsecretor individuals. In contrast, GII.23 primarily binds to B secretor saliva samples. Furthermore, GII.23/24 P domains are able to interact with the H disaccharide, whereas GII.25 exhibits binding affinity for both H disaccharide and B trisaccharide. Crystal structures of GII.23/24/25 P domains revealed high structural similarity, and the complex of GII.25 P domains with H disaccharide was resolved. Single-point mutagenesis identified N352, R353, D382, G443, G444, and H445 as critical residues for H disaccharide binding in GII.25 P domain, while A351 determines glycan-binding specificity.

Discussion: Our findings demonstrate that GII.23/24/25 exhibit glycan-binding patterns similar to most other GII HuNoV genotypes. The structural insights provide a better understanding of virus-host evolution and inform the development of therapeutic strategies against HuNoVs.

Post-apparently successful treatment visceral leishmaniasis (VL), caused by protozoan parasite Leishmania donovani, is often followed by a dermal manifestation among patients known as post-kala-azar dermal leishmaniasis (PKDL). Although non-fatal disorder PKDL manifests itself clinically with a spectrum of cutaneous lesions, including macular, papular, nodular, or polymorphic types, that appear following apparent cure from VL. The absence of reliable non-invasive diagnostic techniques contributes to the underreporting of PKDL, particularly in rural regions. Individuals affected by PKDL may act as reservoirs of Leishmania, posing a significant challenge to ongoing VL elimination initiatives. The transition from VL to PKDL is governed by a complex interplay between host immune mechanisms and parasite-specific genetic polymorphisms. Investigations into the molecular dialog between host and parasite employing both in-vitro and in-silico methodologies are currently underway to elucidate the underlying biological processes. A key objective of these efforts is the identification of reliable biomarkers associated with PKDL, which would facilitate a comprehensive understanding of disease progression and enable the development of improved diagnostic tools for early detection. In this context, genome sequencing has emerged as a critical tool for uncovering genetic variants of L. donovani that contribute to parasite persistence in a subset of individuals, even after effective VL therapy. Insights gained from genomic studies may also reveal novel therapeutic targets and inform vaccine development strategies, thereby opening new avenues for disease control and eradication. This review aims to examine the molecular strategies being employed to investigate the pathophysiology of PKDL, with an emphasis on portraying the mechanistic differences between VL and PKDL. A nuanced understanding of these distinctions is essential for effective disease management, early diagnostic intervention, and interruption of transmission cycles in endemic regions.

Introduction: Pneumonia remains the leading infectious cause of death in children under five, especially in low-resource settings. Reducing mortality requires rapid, accessible, and reliable diagnostic tools. In this regard, the loop-mediated isothermal amplification (LAMP) technique has emerged as a fast and efficient alternative for simple pathogen detection. This study aimed to standardise and optimize a LAMP assay for detecting the main bacteria causing pneumonia in children, including Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, Klebsiella pneumoniae, and Mycoplasmoides pneumoniae using a simple visual readout.

Methods: Several fluorescent and colorimetric dyes were evaluated to identify those providing a clear readout visible to the naked eye. Once achieved, detection conditions for each pathogen in the panel were optimized, and the feasibility of the assay was assessed using respiratory clinical samples, including both confirmed positives and negatives for the bacteria targeted in the panel.

Results and discussion: SYBR Safe, Calcein-Mn²⁺, and SYTO 9 alone did not show a clear differentiation between positive and negative reactions. In contrast, the combination of hydroxynaphthol blue (HNB) and SYTO 9 proved suitable, providing a clear visual readout to the naked eye after optimization of concentrations and reaction conditions. The selected concentrations were 341.25 μM HNB and 0.75 μM SYTO 9, which enabled clear and stable fluorescence-based visualization of LAMP results, remaining visible for several months. The technique showed low detection limits: 3.9 ×10³ CFU/mL for S. pneumoniae, 1.7 ×10⁵ CFU/mL for S. aureus, 8.2 ×10³ CFU/mL for H. influenzae, and 1.27 ×10³ genome copies/reaction for M. pneumoniae. Primers designed to detect K. pneumoniae had high specificity and no cross-reactivity with a sensitivity of 1.5 × 10⁴ CFU/mL. Detection times over 45-50 min may suggest colonization instead of active infection. The evaluation of the technique using clinical samples demonstrated its potential feasibility and applicability in real-world clinical settings. Although standardized under laboratory conditions, this LAMP technique shows promise for detecting major pneumonia-causing bacteria in children and could be particularly valuable in low-resource settings. Its rapid, sensitive, and affordable nature may help improve diagnostics and reduce pneumonia-related mortality. However, larger clinical validation studies are needed to confirm its performance and real-world applicability.

Introduction: Carbapenem-resistant Enterobacterales (CRE) strains carrying bla _NDM variants pose a significant threat to the health of infected patients worldwide.

Methods: This study isolated a carbapenem-resistant Escherichia coli (E. coli) strain carrying bla _NDM-80 from a patient in an intensive care unit in China. Antimicrobial susceptibility testing, whole-genome sequencing (WGS), plasmid transformation assay, cloning experiment, and steady-state kinetic determinations were performed to investigate antimicrobial susceptibility, the characteristics of the genetic environment, the mechanism of resistance gene transmission, resistance gene function, and antibiotic hydrolysis ability.

Results: The results indicated that E. coli carrying bla _NDM-80 showed significant resistance to all β-lactam antibiotics except for aztreonam, aztreonam-avibactam, and cefiderocol. WGS analysis revealed that the strain belonged to sequence type (ST) 155 and the O4:H51 serotype. The bla _NDM-80 was carried by an unconjugated plasmid, and its complete genetic structure was found to be IS5-bla _NDM-80-ble-trpF-dsbD-IS26-nmuD-ISKox3. The bla _NDM-80 had single amino acid substitutions such as V88L, D130N, and M154L compared to bla _NDM-1, whereas it only had the D130N mutation compared to bla _NDM-5. The bla _NDM-80 and bla _NDM-5 had similar antimicrobial resistance profiles. However, in the absence of the native promoter, the minimum inhibitory concentrations (MICs) of bla _NDM-80 for imipenem, meropenem, cefepime, and cefiderocol were twice as high as those of bla _NDM-1. Steady-state kinetic determinations revealed that NDM-80 likely had higher hydrolytic activity against imipenem, meropenem, cefepime, and cefiderocol than NDM-1.

Discussion: This study is the first to report on the emergence of the bla _NDM-80 variant, shedding light on its functional mechanism. Our findings enrich the repertoire of NDM resistance genes and highlight the need for increased surveillance of pathogens harboring bla _NDM variants.