Frontiers in Cellular and Infection Microbiology最新文献

Until recently, nontuberculous mycobacteria (NTM) were not considered as human pathogens. Their nomenclature has evolved over several years, until 1971 when finally named as NTM, which is universally accepted now. Because of continuously evolving diagnostic methods, several new species/subspecies of NTM were identified. Presently, nearly 200 NTM species have been reported. Similar to tuberculosis (TB), NTM are known to involve both pulmonary and extrapulmonary organs. Diagnosis of NTM disease is quite cumbersome and is primarily based on their growth characteristics on solid and liquid cultures. Biochemical testing was the mainstay of NTM diagnosis and species identification in the past, which was often erroneous. Recently, molecular tests like line probe assay, targeted, and whole genome sequencing have become available for rapid and accurate diagnosis. Isolation and identification of NTM species/subspecies alone do not warrant treatment. After ascertaining clinical relevance, virulence of NTM species, and evidence for clinical and radiological progression, the decision to administer treatment is taken. Multiple drugs are often administered for 12 months after sputum culture conversion, except in M. kansasii, and M. szulgai, where this constitutes the total treatment duration, with careful follow‑up for relapse and exogenous new infection. The present review traces the history, evolution of classification of NTM, strides made in the diagnosis and treatment of NTM disease. By integrating these historical lessons on taxonomy, culture phenotypes, genotypes and diagnostic pitfalls with contemporary molecular tools and species/subspecies specific treatment regimens, current practice enables more precise, timely, and patient-centered management of NTM disease.

Objective: The COVID-19 pandemic has profoundly altered global influenza circulation. This study aimed to examine how meteorological factors influenced influenza transmission in Lanzhou, China, across three distinct phases: before, during, and after the COVID-19 pandemic.

Methods: We collected weekly influenza surveillance data and corresponding meteorological indicators for Lanzhou from January 2014 to December 2024. An explainable machine-learning framework integrating XGBoost with Shapley Additive exPlanation (SHAP) values was used to quantify the dynamic impact of environmental factors on influenza virus positivity rates.

Results: From 2014 to 2019, influenza circulation in Lanzhou followed typical northern hemisphere seasonality, with annual winter-spring peaks usually dominated by a single subtype. From 2020 to 2024, however, influenza activity displayed a clear "disruption-to-reconstruction" trajectory. During the COVID-19 pandemic (2020-2022), stringent non-pharmaceutical interventions (NPIs) caused influenza positivity rates and case numbers to collapse, with seasonal peaks nearly disappearing. In the post-pandemic period (2023-2024), influenza epidemics reemerged, but the environmental drivers of transmission-particularly for the dominant Influenza A/H3N2 subtype-shifted substantially. SHAP analyses and relative-contribution assessments consistently showed that environmental influences were strongly masked by NPIs during the pandemic, resulting in markedly reduced explanatory power. After NPIs were lifted, preliminary observation environmental effects resurfaced but in a reshaped pattern: temperature became the predominant driver, with its contribution increasing to nearly 40%, while the influence of humidity, sunshine, and other factors weakened. Although the characteristic winter peak persisted before and after the pandemic, the previously complex, multifactorial environmental model simplified into a more temperature-centric structure in the post-pandemic era.

Conclusion: This study demonstrates that COVID-19 not only temporarily interrupted influenza transmission but also altered the long-term ecological drivers of influenza. Post-pandemic influenza epidemics are entering a new phase, now dominated by a simplified temperature-centered environmental model, suggesting that the climate-influenza relationship has changed after probably major societal intervention. Thus, in Lanzhou and similar climates, the effectiveness of early warning systems based on historical static models requires reassessment and dynamic recalibration. Future influenza surveillance and forecasting will require more flexible frameworks that integrate multi-source data-environmental factors, viral evolution, population immunity, and social behavior-to better address the evolving infectious disease ecosystems.

Background: Shiga toxin (Stx) is the main virulence factor of enterohemorrhagic Escherichia coli, a food-borne pathogen that colonizes the intestine causing gastroenteritis and, in severe cases, hemolytic uremic syndrome. Stx was shown to induce ATP release in vivo and in vitro and blockade of purinergic P2X receptors inhibited its cytotoxicity. Here we investigated the intracellular signaling events preceding ATP release.

Methods: Inhibitors included pertussis toxin, wortmannin, manoalide, 2-aminoethoxydiphenylborate (2-APB), BAPTA-AM and Ca²⁺-free medium. The inositol 1,4,5-triphosphate receptor (IP₃R) was silenced. Stx-induced apoptosis was detected by caspase 3/7 activation. BALB/c mice were injected with Stx2 i.p. Certain mice were pretreated with alpelisib (1 h before and 24 h after Stx2). Kidneys collected after 4 days were stained for phosphatidylinositol 4,5-bisphosphate (PIP2).

Results: Stx1-mediated ATP release in HeLa cells was blocked by pertussis toxin affecting the Gi/o family of G-protein coupled receptors. ATP release was also abrogated by wortmannin, an inhibitor of phosphoinositide 3-kinase (PI3K), by manoalide, inhibiting phospholipase C, by 2-APB inhibiting IP₃R, and by reduction of intracellular calcium (BAPTA-AM) and extracellular calcium (Ca²⁺-free medium). Blocking or silencing the IP₃R protected HeLa cells from Stx1-induced apoptosis. Likewise, blocking the IP₃R reduced Stx2-induced apoptosis. Stx2-challenged mice had distinct PIP2 glomerular staining that decreased in the presence of the PI3K inhibitor alpelisib.

Conclusion: Stx interaction with HeLa cells initiates a signaling pathway involving membrane G protein, PI3K, phospholipase C and IP₃R, ultimately leading to ATP release and promoting cytotoxic effects. The PI3K inhibitor alpelisib altered PIP2 expression in Stx2-challenged mice.

The global spread of multidrug-resistant bacteria poses a serious challenge to effective therapy and public health. The rising resistance to small-molecule antibiotics underscores the limitations of conventional antimicrobial strategies and highlights the urgent need for alternative therapeutic modalities. Lipid nanoparticles (LNPs) have emerged as efficient vehicles for delivering genetic materials, as exemplified by their success in mRNA vaccines. Recent studies suggest that LNPs can also be harnessed to suppress bacterial proliferation and counteract antibiotic resistance through the targeted delivery of nucleic acid cargo. In this review, we discuss recent advances in nanotechnology-based platforms for nucleic acid delivery into prokaryotic systems, with a particular focus on LNPs. We highlight LNPs as a promising delivery system for modulating antimicrobial resistance and bacterial fitness genes. Additionally, we outline key components and formulation strategies required to enable effective nucleic acid delivery against multidrug-resistant bacteria.

Botulism is a rare but severe neurological disease caused by botulinum neurotoxins (BoNTs). Standard diagnostic methods including the mouse bioassay (SMB) and bont gene type-specific PCR, are often limited by the high genetic diversity among bont subtypes, which can lead to false-negative results. The nontoxin-nonhemagglutinin (ntnh) gene is highly conserved and exclusively co-located with the bont gene complex. Thus, this study evaluates the use of ntnh gene as a complementary diagnostic tool for botulism and assesses its association with BoNT types. The ntnh gene was detected in a prospective BoNT-diagnostic group (n=88) and a BoNT-historical group (n=54). Toxin cluster proteins were identified in GenBank and RefSeq Clostridium proteomes using MMSeqs2. ntnh gene detection reinforced positive results from SMB or bont gene tests in 26 cases (35.62% of the total confirmed cases) of foodborne and infant botulism. In two foodborne cases from the BoNT-diagnostic group, the ntnh gene was detected despite negative results from both SMB and bont gene tests, highlighting its potential to identify missed cases. An in silico analysis of 3,250 RefSeq and 2,494 GenBank annotated Clostridium proteomes was conducted. respectively. So, NTNH showed a high co-presence pattern with BoNT. Moreover, NTNH sequences were far more conserved than BoNT sequences in inter-type comparisons (67.2 vs.39.7), which highlights its applicability as a disease biomarker. The ntnh gene analysis is a valuable complementary tool enhancing the diagnosis of botulism. The study highlights the need for clear guidelines to interpret positive ntnh results when direct toxin or bont gene confirmation are negative.

Introduction: Probiotics such as Lactobacillus rhamnosus represent promising alternatives to antibiotics for combating enteric infections, yet their mechanisms of action remain incompletely understood. This study aimed to elucidate the protective mechanisms of L. rhamnosus CIQ249 against enteropathogenic bacterial infection, focusing on the intestinal physical barrier and mucosal immune responses.

Methods: The intestinal colonization ability of CIQ249 was assessed using cFDA-SE labeling and flow cytometry. Growth performance and intestinal morphology were evaluated in mice. Antimicrobial activity of CIQ249 cell-free supernatant was tested against various pathogens, and pathogen damage was visualized by scanning electron microscopy. Protective effects against Salmonella typhimurium and Escherichia coli K99 were examined in a mouse model. Tight junction protein expression was analyzed in vitro and in vivo using immunofluorescence, qRT-PCR, and Western blot. Immune responses- including cytokine production, dendritic cell (DC) activation, T follicular helper (Tfh) cell differentiation, and IgA secretion-were assessed by ELISA, flow cytometry, and immunohistochemistry. Transcriptomic changes in porcine intestinal epithelial cells (PIEC) were analyzed by RNA-seq.

Results: CIQ249 demonstrated strong intestinal colonization and increased villus height and the villus-to-crypt ratio, contributing to improved growth performance. Its cell-free supernatant selectively inhibited enteropathogens and induced structural damage in S. typhimurium and E. coli K99. CIQ249 protected mice from lethal pathogen challenge, preserved intestinal architecture by upregulating tight junction proteins ZO-1 and Claudin-1. It also enhanced mucosal and systemic cytokine levels (IFN-γ, IL-2, IL-4, IL-17, and IL-27), activated DCs, promoted differentiation of CXCR5+CD4+ Tfh and IgA-secreting plasma cells in Peyer's patches, leading to sIgA production. Transcriptome analysis revealed broad modulation of immune- and barrier-related pathways, with validation of key genes (e.g., IL-10, Masp2, Igf2).

Conclusion: CIQ249 enhances mucosal defense against enteropathogenic bacteria through a dual mechanism-strengthening the epithelial barrier and activating a coordinated DC-Tfh-IgA immune axis. These findings provide a multi-level mechanistic basis for its application as a microecological agent against intestinal infections.

Background: Arboviruses pose substantial diagnostic and public health challenges in tropical regions where multiple pathogens co-circulate. Nigeria, with diverse ecological zones and limited surveillance infrastructure, represents a critical nexus for arboviral transmission, yet comprehensive data on seroprevalence, coinfection dynamics, immune modulation, and viral genetic diversity remain scarce.

Methods: We conducted cross-sectional surveillance across three Nigerian ecological zones from January 2019 to December 2023. Sera from 871 participants were tested for IgG and IgM antibodies to dengue virus (DENV), chikungunya virus (CHIKV), Zika virus (ZIKV), yellow fever virus (YFV), West Nile virus (WNV), and Rift Valley fever virus (RVFV) using immunoblot assays. A stratified subset (n=300) underwent cytokine profiling for interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), and interleukin-10 (IL-10). IgM-positive samples underwent RT-PCR confirmation with genotype assignment through sequence comparison against GenBank reference strains.

Results: Overall IgM seropositivity indicating recent infection was 86.8% (756/871), with DENV most prevalent (59.6%; 95% CI: 56.3-62.8%), followed by CHIKV (49.4%), YFV (48.3%), ZIKV (19.7%), WNV (3.4%), and RVFV (2.3%). Coinfection with two or more arboviruses was detected in 61.2% (533/871) of participants. Seropositivity was highest in the tropical rainforest zone (94.2%) compared with Guinea savanna (84.5%) and Sudan savanna (80.4%; χ²=31.8, p<0.001). Cytokine profiling revealed significantly elevated concentrations of IL-6, TNF-α, IFN-γ, and IL-10 in dual and triple infections compared with mono-infections (all p<0.001), demonstrating dose-dependent immune modulation. All four DENV serotypes were identified, with DENV-2 predominating (59.9%). Molecular characterisation confirmed circulation of CHIKV East/Central/South African genotype (82.1%), DENV-2 Cosmopolitan genotype, and both African (71.2%) and Asian (28.8%) ZIKV lineages, with study sequences showing >99% nucleotide identity to established reference strains.

Conclusions: These findings reveal extraordinarily high levels of arboviral infection and coinfection across Nigerian ecological zones. The dose-dependent cytokine elevation in coinfections suggests distinct immunopathological mechanisms. These data underscore the urgent need for multiplex diagnostics, genotype-specific monitoring, and climate-informed vector control strategies.