Emerging Microbes & Infections最新文献

Multiple influenza virus subtypes actively circulate in nature, and assessing their transmissibility provides crucial information for predicting their pandemic potential and for pandemic preparedness. Here, we evaluated the receptor-binding preferences, replication, and transmission of five different influenza viruses (i.e., CA/07-H1N1, GX/18-H1N1, CK/S2283-H3N8, CK/SD007-H9N2, and DK/35-H5N1) in Syrian hamsters. Receptor-binding analysis using biolayer interferometry revealed that four of these viruses preferentially bound α2,6-linked sialic acid receptors, whereas the H5N1 virus bound to α2,3-linked and α2,6-linked sialic acid receptors similarly. All five viruses replicated well in the respiratory tissues of Syrian hamsters, but did not cause obvious symptoms or death, indicating that Syrian hamsters can tolerate influenza virus infection and are not suitable for influenza virus pathogenicity studies. The four viruses that bound to α2,6-linked sialic acid receptors with higher affinity than to α2,3-linked sialic acid receptors were transmissible between Syrian hamsters via direct contact or respiratory droplets; however, the H5N1 virus was not transmissible through respiratory droplets, consistent with previously reported transmission characteristics observed for these viruses in guinea pigs and ferrets. Given that Syrian hamsters and humans have similar receptor expression patterns in their nasal mucosa, our findings suggests that Syrian hamsters can be used as a suitable animal model for evaluating the transmissibility of influenza viruses that preferentially bind to α2,6-linked sialic acid receptors.

Linezolid-resistant Clostridioides difficile, conferred by the acquisition of cfr-like genes, has been reported in Europe and America. However, the emergence of linezolid resistance in C. difficile in the Asia-Pacific region and its impacts on C. difficile pathogenicity remain unclear. In this study, 881 C. difficile isolates from the Asia-Pacific region were screened for cfr-like genes. Whole genome sequencing was performed on 16 cfr-like gene-positive isolates from four countries. Thirteen isolates possessed cfr(B), which was located within Tn6218, while three isolates possessed cfr(C), which was located within the integrative and conjugative elements (ICE) F548 and DA275. Fourteen (87.5%, 14/16) of the cfr-like gene-positive isolates were resistant to linezolid. In comparison to the two isolates susceptible to linezolid, these 14 isolates exhibited significantly higher mRNA expression levels of cfr(B) and cfr(C), along with significantly higher bacterial density at 12 h. Conversely, they demonstrated reduced abilities for sporulation and biofilm formation. After the cfr(B) gene was knocked down by the CRISPR interference, the C. difficile strain presented lower bacterial density at 12 h, higher toxin production and stronger sporulation and biofilm formation abilities. Our findings reveal the emergence of cfr-like genes C. difficile isolates in the Asia-Pacific region, highlighting that cfr-like genes not only mediate linezolid resistance but also contribute to regulating pathogenic potential. Linezolid resistance in CDI should be closely monitored in specific patients.

Current anti-tuberculosis treatments primarily target extracellular Mycobacterium tuberculosis (Mtb), but exhibit limited efficacy against intracellular Mtb, leading to incomplete clearance of pathogens and an increased risk of recurrence. Antimicrobial peptides (AMPs) possess broad-spectrum antimicrobial activity and low potential for resistance development. Here we developed an in vitro mRNA expression platform which not only facilitates intracellular AMPs expression within macrophages, but also significantly enhances their bactericidal activity against Mtb post-infection. Notably, the combination of AMPs trimers demonstrated superior anti-Mtb activity compared to individual AMPs or other combinations. Furthermore, fusion of this AMP complex with either the minor tail protein Gp6 or lysin Gp10 from Mycobacterium phage L5 substantially improved macrophage-specific targeting and intracellular Mtb elimination. Thus, our current study provides novel insights and innovative strategies for the treatment of tuberculosis or other intracellular bacterial pathogens.

AbstractMultiple mechanisms underpinning biofilm antimicrobial resistance (AMR) have been studied individually. This study aimed to integrate these mechanisms, to understand their contributions to staphylococcal biofilm AMR, as a part of a whole, and to elucidate key hurdles hindering effective biofilm eradication by antimicrobial agents.Nine antibiotics were selected against microplate-based biofilms formed by Staphylococcus aureus ATCC 25923 and Staphylococcus epidermidis RP62A. Four mechanisms, including repressed bacterial metabolism, the barrier effect of the biofilm extracellular polymeric substances (EPS) matrix, the acidic inner-biofilm pH, and inoculum effects associated with high-cell-density biofilm growth were studied. The impact of individual mechanism on biofilm AMR was quantitated by determining the fold increase of concentration that allows antibiotics to overcome the mechanism. Antibiotic concentrations were then incrementally increased from minimum bactericidal concentration (MBC) to sequentially address all four mechanisms, ultimately aiming to kill at least 99.9% of biofilm cells.A simplified method was developed to evaluate the dependence of antibiotics on bacterial metabolic states for the lethality. Gentamicin, tobramycin and ciprofloxacin at 1,024 µg/mL overcame all four mechanisms and successfully killed S. aureus ATCC 25923 biofilms by at least 3 log units. Ciprofloxacin at 1,024 µg/mL effectively killed S. epidermidis RP62A biofilms. The contribution of each mechanism to biofilm AMR was strain- and drug- dependent, with low-cell-metabolism being the most important factor.This study underscores the individual contributions of each mechanism to staphylococcal biofilm AMR and highlights the necessity of targeting all four mechanisms to achieve effective biofilm eradication.

Understanding the mechanisms underlying the emergence and spread of high pathogenicity avian influenza virus (HPAIV) is critical for tracking its global dissemination, particularly via migratory seabirds, given their role in transmission over long distances. Scavenging seabirds, such as skuas, may act as both reservoirs and vectors, and have been linked to multiple outbreaks since 2021. Here, we report the detection of HPAIV H5N1 clade 2.3.4.4b in three Tristan skua (Stercorarius antarcticus hamiltoni) carcasses on Gough Island in the central South Atlantic Ocean. To investigate potential incursion routes, we combined genomic analyses with year-round tracking data from global location sensors. Although migratory movement patterns suggested southern Africa as the most obvious pathway, the strain detected on Gough Island was more closely related to that identified in South Georgia, indicating that infection may have occurred during the pre-laying exodus, when skuas disperse into frontal waters south of the island. No further cases have been confirmed for Gough, but more systematic monitoring is needed to understand the dynamics of virus infection. The detection of HPAIV H5N1 in skuas on Gough Island highlights the importance of continued vigilance, proactive and geographically inclusive surveillance strategies, and biosecurity measures globally, alongside efforts to reduce other pressures on globally important seabird populations to help strengthen their resilience.

Older adults remain highly vulnerable to severe SARS-CoV-2 outcomes despite multiple vaccinations, yet age-associated differences in immune responses to updated COVID-19 booster vaccines remain incompletely characterized. Here, we administered an XBB.1.5 trivalent recombinant protein booster (WSK-V102C) to 22 individuals (<38 years) and 20 individuals (≥73 years), all of whom had previously received 2-3 doses of inactivated COVID-19 vaccines. Neutralizing antibody responses against multiple SARS-CoV-2 variants were quantified and compared between age groups. Meanwhile, single-cell RNA sequencing was also performed on peripheral blood mononuclear cells (PBMCs) collected at baseline and 28 days post-vaccination to profile age-associated immune features following boosting. Following booster immunization, both age groups achieved significantly elevated antibody titers against all tested strains. Nevertheless, the magnitude of antibody fold increase was consistently lower in elderly individuals than in younger adults. Single-cell analyses revealed age-associated differences in post-vaccination immune organization. In elderly individuals, B-cell state transitions were characterized by transcriptional signatures consistent with memory B cell-to-plasmablast differentiation, whereas younger individuals predominantly exhibited transitions from naïve B cells. CD4+ T cells from elderly individuals displayed altered transcriptional trajectories and reduced T-cell receptor diversity relative to younger adults. In contrast, younger individuals showed coordinated B- and T-cell-associated transcriptional programs, including enrichment of transcription factors such as KLF7, CEBPB, CEBPD, and MAFB. Collectively, our study describes age-associated differences in immune coordination and cellular response patterns following XBB.1.5 booster vaccination. Further longitudinal and functional studies will be required to clarify the mechanistic basis and clinical implications of these observations.

Tuberculosis (TB) remains a global health challenge, exacerbated by the emergence of drug-resistant Mycobacterium tuberculosis strains. Most methods for drug susceptibility testing (DST) are culture-dependent and time consuming, possibly delaying optimal TB-treatment. This study aimed to develop an extensive targeted next-generation sequencing (tNGS) approach for rapid genotypic DST directly from clinical samples. We designed a tNGS panel comprising 30 amplicons targeting 19 genomic regions associated with resistance to 20 antibiotics. This method was applied to 71 smear-positive (0-3+) pulmonary TB clinical samples collected at the Portuguese National Reference Laboratory. DNA was extracted and amplified using multiplex PCRs, followed by sequencing on Oxford Nanopore Technologies MinION platform. Sequencing data were analysed using TB-Profiler and the tNGS results compared to phenotypic DST and whole genome sequencing (WGS) data from corresponding isolates. The tNGS demonstrated high concordance with both phenotypic and WGS-based DST across different sample types and smear positivity levels. For first-line drugs, tNGS showed 88% categorical agreement (CA) with pDST, increasing to 97% when excluding undetermined results. Compared to WGS across all analysed antibiotics, tNGS achieved 92% CA, increasing to >99% when excluding undetermined results. Validation of the tNGS panel showed 90% (1,895/2,076) of amplicons reaching >10x coverage at all analysed positions and 43 (61%) samples with all complete amplicons above this threshold. Non-specific amplification of contaminant bacterial DNA was minimal, with most mapped off-target reads being of human origin. This method enables comprehensive resistance prediction directly from clinical samples and signifies an important development in TB diagnostics and resistance monitoring.

Streptococcus suis serotype 2 (SS2), a significant zoonotic pathogen, initiates systemic infection by breaching the respiratory epithelial barrier. Ferroptosis, an iron-dependent form of regulated cell death driven by lipid peroxidation, is increasingly implicated in the pathogenesis of various infectious diseases, yet its role in SS2-induced epithelial barrier dysfunction remains unknown. Here, we demonstrate SS2 infection sensitizes airway epithelial cells to ferroptosis, leading to the accumulation of lipid peroxides, upregulation of the transcriptional repressor Snail1, and subsequent downregulation of intercellular junction proteins. This cascade compromises epithelial integrity and promotes bacterial translocation. Mechanistically, we found SS2 overwhelms the cellular redox defense system and identified bacterial eukaryotic-like serine/threonine kinase 1 (Stk1) as the key mediator of this process. Stk1 directly interacts with host protein Keap1, which stabilizes the Keap1-Nrf2 complex. This stabilization enhances the ubiquitination and subsequent proteasomal degradation of Nrf2, the master regulator of antioxidant response, thereby crippling cell's ability to neutralize lipid peroxides. In summary, this study unveils a novel virulence mechanism wherein SS2 effector Stk1 promotes Nrf2 degradation to trigger ferroptosis, ultimately leading to the disruption of respiratory epithelial barrier. These findings suggest that inhibiting ferroptosis could represent a promising therapeutic strategy for clinical prevention and treatment of SS2 infections.