Yuelan Yin

Listeria monocytogenes is a Gram-positive zoonotic pathogen responsible for listeriosis, a severe foodborne disease with high mortality in humans and animals. This study aimed to investigate the molecular epidemiology and genomic characteristics of L. monocytogenes isolated from raw yak meat in Nyingchi, Xizang, China. A total of 231 yak-related samples were collected in Nyingchi, consisting of 214 retail raw yak meat samples, 14 farm environmental samples, and 3 nearby water source samples. L. monocytogenes isolates were identified and characterized using culture-based methods, PCR serotyping, and whole-genome sequencing (WGS). Bioinformatic analyses were performed for virulence, antimicrobial resistance, and functional gene annotation using KEGG and COG databases. The overall contamination rate of Lm was 13.08% (28/214) for retail raw yak meat samples, whereas no isolates were recovered from 14 farm environmental samples (0.00%, 0/14) and 3 nearby water source samples (0.00%, 0/3). The serotypes of isolates were 1/2a (9/28, 32.14%), 1/2b (7/28, 25.00%), and 1/2c (12/28, 42.86%). These 28 isolates exhibited varied antimicrobial resistance profiles, with universal resistance to trimethoprim-sulfamethoxazole, high resistance to erythromycin and clindamycin, and low resistance to vancomycin. MLST analysis revealed seven sequence types (STs): ST9 (12/28, 42.86%), ST619 (6/28, 21.43%), ST8 (6/28, 21.43%), ST7 (1/28, 3.57%), ST87 (1/28, 3.57%), ST121 (1/28, 3.57%), ST297 (1/28, 3.57%). ST619 isolates harbored multiple virulence genes, including those located on Listeria pathogenicity islands LIPI-1, LIPI-3, and LIPI-4, indicating high genomic potential for virulence. Representative isolate Y2 (ST619) possessed a 3,009,858 bp genome with 3036 coding genes, four genomic islands, and two prophages. Functional annotation revealed enrichment of genes involved in carbohydrate transport and metabolism and amino acid biosynthesis pathways. Our findings provide the first genomic insight into L. monocytogenes contamination in yak meat from Nyingchi, Xizang, China, highlighting the urgent need to strengthen food safety monitoring and hygiene management in this region.

Listeria monocytogenes is a formidable foodborne zoonotic pathogen with a ubiquitous environmental distribution and a remarkably broad host range [1]. Pregnant women, neonates, and immunocompromise...

Listeria ivanovii (Liv) is an anaerobic intracellular pathogen primarily responsible for listeriosis in ruminants, presenting with clinical manifestations

Listeria monocytogenes (Lm) is a facultative intracellular pathogen responsible for life-threatening listeriosis, characterized by high mortality rates. Currently, there is no vaccine available for the prevention or treatment of listeriosis. Here, we developed two adjuvanted inactivated vaccines and evaluated their safety, immunogenicity, and protective efficacy. The hypervirulent Lm strain XYSN was inactivated with β-propiolactone (BPL) and formulated with AddaVax or Alum to produce inactivated vaccines (ADIV and ALIV) respectively. Local reactogenicity and histopathological observations revealed no adverse reactions in a murine model. Humoral assays demonstrated both ADIV and ALIV induced higher antibody titers against Lm XYSN, with ADIV eliciting stronger cellular immune responses, as indicated by increased IL-17 and IFN-γ expression in spleen cells. Notably, ADIV conferred 83.3% protection against a lethal challenge with hypervirulent Lm strain, representing a 50% increase compared with the 33.3% protection achieved by ALIV. AddaVax adjuvant not only augmented humoral responses to inactivated bacterial cells but also elicited stronger cellular immune responses compared to Alum adjuvants, resulting in enhanced immune protection. This research offers insights into developing novel inactivated vaccines for listeriosis prevention, particularly beneficial for immunocompromised individuals.

Histomonosis, caused by Histomonas meleagridis, leads to economic losses in the poultry and livestock industry. In recent years, studies on the role of intestinal microbiota in host physiological health have attracted growing attention. Understanding the changes in gut bacterial communities of chickens is crucial for improving poultry and livestock production. This study investigated the impact of Histomonas meleagridis infection on the growth performance, overall health, and cecal microbiota composition of chickens. Body weight changes and pathological alterations were assessed at different time points post-infection through animal experiments, with 7 days post-infection defined as the early stage and 14 days as the peak stage of infection. Cecal content samples were collected from the 7-day control group (G1), 7-day infected group (G2), 14-day control group (G3), and 14-day infected group (G4) for 16S rRNA sequencing analysis. The microbial diversity analysis revealed that H. meleagridis infection altered the number of microbial species in the cecal microbiota of chickens. The alpha diversity index was significantly reduced (p < 0.05), and principal coordinate analysis (PCoA) revealed significant structural differences between infected and control groups (p = 0.001). Taxonomic composition analysis showed that beneficial gut bacteria, such as Firmicutes and Lactobacillus spp., decreased in abundance, whereas Bacteroidota, Proteobacteria, Escherichia spp., and Fusobacterium mortiferum were enriched in the infected group. LEfSe analysis indicated that G1 was enriched with Oscillospiraceae and Blautia; G2 with Christensenellaceae; G3 with Verrucomicrobia and Lactobacillus aviarius; and G4 with Proteobacteria and Fusobacteria. In conclusion, H. meleagridis infection markedly altered the cecal microbiota composition by shifting the relative abundances of beneficial and pathogenic bacteria, resulting in reduced microbial diversity.

Listeriosis is a severe zoonotic disease caused by Listeria monocytogenes (L. monocytogenes), which poses a significant threat to both livestock and public

Among the 14 serovars of Listeria monocytogenes (Lm), serovar 4b strains are the most predominant isolates linked to human listeriosis outbreaks‐a phenotype associated with their unique wall teichoic acid (WTA) decorated with galactose (Gal) and glucose (Glu). A wealth of knowledge is available for galactosylated‐WTA (Gal‐WTA) manipulating bacterial homeostasis and virulence, whereas the relationship between glucosylated‐WTA (Glu‐WTA) and Gal‐WTA in listerial physiology and pathogenesis remains unclear. Here, we find that Glu‐WTA and Gal‐WTA jointly constitute the O‐antigen pattern of serovar 4b Lm; however, Glu‐WTA specifically serves as the indispensable ligand for listeriophage LP4 adsorption. Moreover, the co‐operation between Glu‐ and Gal‐WTA increases biofilm formation and bacterial resistance to cationic antimicrobial peptide (CRAMP). We further demonstrate that Gal‐WTA modulates the anchoring of surface proteins, including IspC, Ami, and InlB. Additionally, dual glycosylated WTA interaction with ActA facilitates bacterial intracellular motility and dissemination. Consistently, Glu‐WTA significantly enhances bacterial colonization ability in the mesenteric lymph nodes (MLNs), ileum, liver, and brain of mouse, cooperating with Gal‐WTA to facilitate Lm dissemination to distant organs and tissues. In conclusion, we reveal the crucial roles of Glu‐WTA in synergizing with Gal‐WTA to modulate the integrity of the cell wall structure and exacerbate bacterial infection, providing a global understanding of the hypervirulence and pathogenicity of invasive serovar 4b Lm.