Microbiology and Immunology最新文献

Vibrio parahaemolyticus is a leading cause of seafood-borne gastroenteritis worldwide, and its pathogenic strains typically harbor thermostable direct hemolysin (TDH) and type III secretion system 2 (T3SS2). Although these virulence factors are associated primarily with clinical isolates, their presence in nonclinical environmental and food isolates raises concerns about their potential infection risk. In this study, we investigated the pathogenic potential of nonclinical V. parahaemolyticus isolates from Vietnam, which share serotypic and genotypic characteristics with pandemic strains. Serotyping and genetic analysis of 56 isolates (35 clinical and 21 nonclinical) revealed that two nonclinical isolates from shrimp and environmental water carried the tdh gene, T3SS2α genes, and pandemic markers that clustered phylogenetically with the pandemic strains. Protein expression assays confirmed that these isolates secreted TDH and the T3SS2 translocator (VopD2) at levels similar to those in the clinical reference strain. Bile exposure induced T3SS2-related gene expression, which suggests a conserved gene regulatory mechanism. Enterotoxicity evaluated using a rabbit ileal loop assay showed that two nonclinical isolates induced significant fluid accumulation. Genetic deletion and complementation experiments confirmed that T3SS2 was essential for enterotoxicity. These findings provide the first experimental evidence that nonclinical pandemic strains of V. parahaemolyticus possess functional enteric virulence mechanisms and suggest their potential as infection sources in endemic regions.

The survival of Pseudomonas aeruginosa (PA) is a major factor in causing chronic or acute lung infections in individuals with compromised immune systems. Being the initial line of defense against infections, macrophages use a variety of tactics to fight intracellular bacteria, which are intimately linked to ferroptosis. It is yet unknown, nevertheless, what function ferroptosis serves in PA-infected macrophages. Initially, we established a macrophage infection model with PA to investigate the infection levels and duration using Cell Counting Kit-8 (CCK-8) and fluorescence microscopy and assessed the intracellular quantity of PA by counting colony forming units (CFUs). Subsequently, changes in ferroptosis-related characteristics in macrophages infected with PA were detected through quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blot analysis, and fluorescence probes. Furthermore, the relationship between PA infection and ferroptosis in macrophages, as well as the specific mechanism regulating nuclear factor erythroid 2-related factor 2 (NRF2) protein stability, was validated by constructing NRF2 knockdown cells. Finally, the binding of PA to Kelch-like ECH-associated protein 1 (KEAP1) in macrophages was detected using Co-Immunoprecipitation (Co-IP) and protein thermal stability analysis. Under optimal conditions (multiplicity of infection (MOI) = 15:1, t = 72 h), it was demonstrated that macrophages infected with PA resisted ferroptosis, as confirmed by ferroptosis-related assays. Subsequent construction of NRF2 knockdown cells showed that PA-mediated resistance of macrophage ferroptosis depended on NRF2. Mechanistically, it was proved that PA stabilized NRF2 protein expression by inhibiting ubiquitin-proteasome-mediated protein degradation and competitively binding to KEAP1. In conclusion, this study demonstrated that PA stabilized NRF2 protein expression in macrophages, inducing resistance to ferroptosis through the ubiquitin-proteasome pathway and competitive binding to KEAP1.

Influenza is generally understood to be transmitted through inhaling virus-contaminating aerosol/droplets or contact with virus-contaminated environmental surfaces (or fomites). However, the risk associated with transmission through contact with fomites is hypothetical, lacking solid quantitative evidence. In our previous paper, we demonstrated through a series of experiments that the probability of influenza virus transmission from touching contaminated surfaces of face masks is minimal (Sci Rep 2024, 14, 20211). In the present study, we expanded upon this study by conducting an experimental evaluation of the likelihood of influenza transmission from dried fomites under three specific scenarios: (1) when a floor/table lies within the trajectory of artificial coughs, (2) when stainless-steel door levers are exposed to viral spraying (simulating cough), and (3) when door levers are exposed to viruses on the grasping hand. The fingertips contacting the above fomites formed on the surfaces were washed into a rinsing medium. Subsequently, we evaluated the rinsing medium for viral content using plaque-forming assay to detect the viable viruses and real-time quantitative PCR assay to detect the viral genes. We found that viable viruses were rarely transmitted to fingertips from the above fomites even when the viral loads in the viral fluid contaminating the fomites far exceeded that seen in real life. Consequently, we conclude that the probability of contact transmission of influenza via dried fomites is negligible or minimal under the scenarios studied here.

Antibiotic-resistant bacteria have become a significant global threat to public health due to the increasing difficulty in treatment. These bacteria acquire resistance by incorporating various antibiotic resistance genes (ARGs) through specialized gene transfer mechanisms, allowing them to evade antibiotic attacks. Conjugation, transformation, and transduction are well-established mechanisms that drive the acquisition and dissemination of ARGs in Gram-negative bacteria. In particular, the horizontal transfer of plasmids carrying multiple ARGs is highly problematic, as it can instantly convert susceptible bacteria into multidrug-resistant ones. Transduction, mediated by bacteriophages that package ARG-containing chromosomal DNA from host cells, also plays a crucial role in ARG spread without requiring direct cell-to-cell contact. Recently, a novel horizontal gene transfer (HGT) mechanism involving outer membrane vesicles (OMVs) has been identified as a key player in ARG dissemination. OMVs—nanoscale, spherical structures produced by bacteria during growth—have been found to carry small plasmids and chromosomal DNA fragments containing ARGs from their host bacteria. This newly discovered transfer process, termed “vesiduction,” enables intercellular DNA exchange and further contributes to the spread of antibiotic resistance. Additionally, mobile genetic elements such as transposons, insertion sequences, and site-specific recombination systems like integrons facilitate rearrangement of ARGs, including their translocation between chromosomes and plasmids. This review explores the molecular mechanisms underlying the HGT of ARGs, with a particular focus on clinically isolated antibiotic-resistant Gram-negative bacteria.

The analysis of bacterial infections using animal models has primarily relied on the average evaluation of many individuals at specific time points. Consequently, tracking temporal changes in an infection within the same individual is challenging. InVivo imaging techniques enable the longitudinal assessment of infection in the same individual while reducing the number of animals required. Understanding the dynamics of bacterial infections over time is crucial for elucidating disease mechanisms and developing effective treatment strategies. In this review, we summarize the In Vivo imaging techniques used to detect bacterial colonization in deep tissues in animal models of bacterial infection, along with efforts to enhance their sensitivity. In particular, we introduce a recently developed In Vivo imaging system that employs near-infrared luminescence to achieve high sensitivity and versatility. Furthermore, we discuss strategies for further improving its sensitivity.