Search Results (443)

Riemerella anatipestifer (R. anatipestifer) is a pathogenic bacterium belonging to the genus Riemerella within the family Flavobacteriaceae, which has multidrug resistance (MDR) and can cause high pathogenicity in waterfowl. The aim of this study was to investigate the antimicrobial resistance and genomic characteristics of R. anatipestifer strains isolated from several regions of China from 2023 to 2024. Two strains were selected for challenge tests, and virulence protection tests were conducted on florfenicol-resistant and florfenicol-sensitive strains. A total of 88 strains of R. anatipestifer were collected from the Shandong, Jiangsu, Guangdong, Hebei and Henan regions. The results showed that the 88 strains included serotypes 1, 2, 5, 6, 7 and 10. Serotype 5 was the most prevalent in the Shandong region. All strains were multidrug-resistant, with the hexaresistance accounting for the highest proportion (42.1%). A total of five resistance genes (tet(X), floR, ermF, qnrS, rmtB) and seven virulence genes were found (ompA, camp, AS87_04050, SIP, Fur, TbdR1, luxE). The challenge test showed that the LD₅₀ of RA12 was 2.75 × 10⁷ CFU/mL, and that of RA26 was 2.57 × 10⁷ CFU/mL. Phylogenetic tree analysis revealed that strain RA26 was closely related to strain 20190403E1-1, and strain RA16 was closely related to strain JW1. In addition, serotypes 2 and 7 identified in this study have been undergoing clonal transmission in China. Virulence protection tests indicated that the results of in vitro drug susceptibility tests were consistent with the therapeutic effects after in vivo treatment, and no R. anatipestifer was found in the visceral tissues of surviving ducklings. This study provides a reference for the rational use of antibiotics. Full article

Introduction: Cholera remains a major public health threat in endemic settings, and oral cholera vaccine (Shanchol™) campaigns are increasingly used amid constrained global supply. However, practical decisions on revaccination require clearer, setting-specific estimates of how rapidly vaccine-induced vibriocidal antibodies peak and wane. Methods: We conducted a prospective cohort kinetics analysis in Lukanga Swamps (Central Province, Zambia), enrolling adults (18–65 years) stratified by prior Shanchol™ exposure (0, 1, or 2 previous doses). All participants received two Shanchol™ doses 14 days apart, with serum collected at baseline and days 14, 28, 60, and 90 (end of follow-up). Ogawa and Inaba vibriocidal titres were measured using a complement-based assay and analysed on the log10 scale. Serotype-specific mixed-effects models with natural cubic splines for time (knots: 14, 28, 60 days) assessed trajectories by prior-dose strata, adjusting for age, sex, and HIV status. Peak timing and post-peak half-life were derived from model-based predictions with participant-level bootstrap CIs (1000 replications). Results: The analysis included 225 participants: 68 (30.2%) with zero prior doses, 89 (39.6%) with one, and 68 (30.2%) with two; median age was 33 years (IQR 25–49), 56.4% were female, and 19.2% were HIV-positive. Modelled titres for both serotypes rose steeply after vaccination, peaking around day 36–37 across prior-dose strata. Ogawa titres reached half of peak by about day 73–78, corresponding to post-peak half-lives of 37–41 days; Inaba declined more slowly with half-lives of 42–46 days. Confidence intervals overlapped across prior-dose strata, indicating minimal differences by vaccination history. Conclusions: In this cholera-endemic adult population, Shanchol™ induced vibriocidal responses that peaked at ~5 weeks and waned over the following 5–7 weeks, with broadly similar kinetics regardless of prior vaccination and slightly slower decay for Inaba than Ogawa. These parameters can inform booster timing in hotspot settings. Full article

Background: Streptococcus pneumoniae (Spn) is a leading bacterial pathogen responsible for severe invasive diseases, including meningitis, sepsis, and pneumonia. Current pneumococcal vaccines, which are all based on capsular polysaccharide antigens, provide limited protection and are further compromised by post-vaccination serotype replacement. Pneumococcal surface protein A (PspA), a highly conserved virulence factor expressed across diverse serotypes, has emerged as a promising candidate antigen for novel protein-based vaccines. However, progress in this field has been hindered by the absence of standardized in vitro functional antibody assays. Methods: This study established a robust functional antibody detection method for PspA-based protein vaccines by modifying the conventional multiplex opsonophagocytic killing assay (MOPA), originally designed for polysaccharide-based vaccines. Using polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) typing, a target strain panel was selected and developed to include representative strains from PspA Family 1-Clade 2 and Family 2-Clades 3 and 4. The MOPA protocol was optimized by extending the phagocytic reaction time to enhance sensitivity. Specificity was confirmed through recombinant PspA competitive inhibition assays. Results: The assay demonstrated high linearity (R² ≥ 0.98) between opsonophagocytic index (OI) and serum dilution, along with acceptable repeatability (CV ≤ 30%) and intermediate precision (CV ≤ 50%). Both preclinical and clinical serum samples exhibited potent bactericidal activity against diverse PspA families, independent of capsule type. Conclusions: This study provided a standardized framework to support the development and regulatory assessment of protein-based pneumococcal vaccines. Full article

Background: Pneumococcal diseases remain a global threat due to the serotype-specific limitations of polysaccharide vaccines. This study evaluated a recombinant protein-based pneumococcal vaccine (PBPV) combining three PspA variants (PRX1/Family1Clade2, P3296/Family2/Clade3, P5668/Family2/Clade4) and detoxified pneumolysin (PlyLD). PspA targets conserved surface epitopes to block immune evasion and achieve broad coverage, while PlyLD neutralizes pore-forming toxins and enhances adaptive immunity. Methods: We evaluated the safety and immunogenicity of the PBPV in animal models. Acute toxicity studies were conducted by administering a single intramuscular injection to ICR mice, whereas chronic toxicity and immunogenicity studies were performed in cynomolgus monkeys via repeated intramuscular injections, with an equal number of male and female animals in both groups. Immune responses were assessed using ELISA, multiplexed opsonophagocytic killing assays (MOPAs), and neutralizing antibody assays. Results: Acute toxicity studies in ICR mice showed no signs of abnormal toxicity or irritation at one-dose levels. In the chronic toxicity study, cynomolgus monkeys received repeated intramuscular injections once every 3 weeks for a total of four administrations, at doses of one dose/monkey and five doses/monkey, followed by a 4-week recovery period. No significant systemic toxic reactions were observed, and the safe dose was determined to be five doses/monkey. In the immunogenicity study of monkey serum, both low-dose and high-dose groups demonstrated significant increases in antigen-specific IgG titers against each component; opsonophagocytic killing activity against pneumococcal strains from Clades 2, 3, and 4 from PspA Families 1 and 2; and neutralization antibody titers against pneumolysin post-vaccination. Conclusions: The recombinant protein-based pneumococcal vaccine exhibited a favorable safety profile and potent immunogenicity in animal models, indicating promise for broad protection against pneumococcal disease. These findings support the further development of PBPVs as a viable alternative to conventional polysaccharide-based vaccines. Full article

Background: Dengue virus (DENV) is becoming a global public health problem, but the immunogenicity of DENV structural proteins is not fully understood. Methods: We predicted the epitope-based immunogenicity of DENV proteins from four serotypes in silico and evaluated their efficacy in vitro (T-cell proliferation assays) and in vivo (ELISpot, qRT-PCR, and plaque reduction neutralization tests using murine splenocytes). We focused on the envelope protein, which contains envelope domain III. Immunogenic B-cell epitopes were predicted using BepiPred-2.0, and regions that induce T cell-mediated immune responses were analyzed using the immune epitope database (IEDB), which validates peptides presented on HLA class I. Results: Nine-amino-acid peptide candidates were selected based on a score of >0.1. The best peptide candidates were tested in T-cell proliferation assays to confirm the in silico data. Subsequently, BALB/c mice were vaccinated with candidate peptides showing immunity in the proliferation assay, and their splenocytes were analyzed. ELISpot and qRT-PCR data showed that some candidate peptides highly regulated cytokines, including interferon-γ, tumor necrosis factor-α, and interleukin-4. Murine sera were collected after peptide boosting 2 weeks apart. Stimulation of cellular immunity was confirmed for some candidates in plaque reduction neutralization tests. Full article

(1) Background: Listeria monocytogenes (Lm) is recognized by the World Health Organization (WHO) as one of the four principal foodborne pathogens. This study aimed to investigate the molecular characteristics of Lm isolates from Jiaxing, China, using whole-genome sequencing (WGS) to enhance our understanding of their molecular epidemiology. (2) Methods: A total of 39 foodborne Lm isolates and 7 clinical Lm isolates were analyzed via WGS to identify resistance genes, virulence factors, lineage, sequence type (ST), and clonal complex (CC). Antibiotic susceptibility was assessed using Minimum Inhibitory Concentration (MIC) testing, and serotypes were confirmed via multiplex PCR. (3) Results: We found that 39 food isolates were mainly lineage II (66.67%), with 13 STs; ST8 was the dominant ST, and 2 new types, ST3210 and ST3405, were found. Among the seven clinical isolates, lineage I was dominant (57.14%), and ST87 was the dominant ST. Serotype 1/2a was dominant, accounting for 54.35%, followed by 1/2b, which accounted for 36.96%. The overall antimicrobial resistance rate was 13.04%, with a multidrug resistance rate of 2.17%. All strains harbored LIPI-1 and LIPI-2, and five strains carried LIPI-3 genes: one strain belonged to ST619 of lineage I, two strains belonged to ST224 of lineage I, and two strains belonged to ST11 of lineage II. (4) Conclusions: This study clarified the genotype and serotype characteristics of Listeria monocytogenes in Jiaxing, as well as their molecular characteristics relating to drug resistance and virulence, thus providing a technical basis for improving exposure risk assessment of Listeria monocytogenes. Continuous monitoring, prevention, and control are recommended to further improve regional public health and safety. Full article

The world is divided into seven regional pools based on the serotype distribution and geographical spread of the foot-and-mouth disease (FMD) virus. The Republic of Korea (ROK) belongs to Pool 1, where serotypes O, A, and Asia1 are endemic. Recently, the risk of incursions by the O/CATHAY topotype has increased in Pool 1, raising concerns about its potential introduction into the ROK. To assess the protective effectiveness of three commercial FMD vaccine strains—O1/Manisa + O/3039, O/Primorsky, and O1/Campos—currently used in the ROK against this topotype, an animal challenge experiment was conducted. Three treatment groups (n = 4 in each) of pigs received a single 2 mL injection of one of the vaccines at 8–10 weeks of age, and the other group (n = 2) served as the control. All pigs were challenged with the O/HKN/5/2019 virus (O/CATHAY topotype) at 21 days post-vaccination. All vaccines conferred protective effects, with O1/Campos demonstrating the highest efficacy by inducing fewest clinical signs and significantly reducing virus shedding in the treated groups compared with those in the control group. These findings suggest O1/Campos may serve as an emergency measure; nevertheless, the development of a vaccine specifically targeting the O/CATHAY topotype is warranted. Full article

S. suis is a prominent zoonotic pathogen responsible for diseases such as arthritis in piglets, swine septicemia, and meningitis. The emergence of multi-drug resistance (MDR) underscores the urgent need for the development of novel antibacterial strategies. In this context, a systematic evaluation of the antibacterial potential of the bacteriophage lytic enzyme Ply900 was conducted in this study, along with an analysis of its domain functions and an in vivo study of its therapeutic dynamics. Ply900 exhibits potent in vitro lytic activity against multiple bacteria, including Streptococcus suis, Streptococcus agalactiae, and Staphylococcus aureus. Notably, it possesses broad biochemical stability, with tolerance to diverse environmental conditions. In a mouse model of S. suis serotype 2 SC19 infection, both the direct Ply900 treatment group and the triple therapy group achieved effective eradication of S. suis, with markedly improved survival rates. The remaining bacteria remained susceptible to Ply900, with no evidence of induced resistance development. Mechanistic analysis revealed that the SH3B domain of Ply900 enhances targeted cleavage efficiency by binding synergistically to peptidoglycan with the CHAP domain, with CYS-34, HIS-59, and ASP-28 serving as key amino acid sites for Ply900’s cleavage activity. Collectively, these findings lay the foundation for the potential dual applications of the lysin Ply900, both in the clinical treatment of S. suis infections and in the prevention and control of these pathogenic bacteria in livestock farming. Full article

(1) Background: As an innovative drug derived from botulinum neurotoxin serotype E, TrenibotulinumtoxinE^® demonstrates a rapid onset and shorter effect. Due to concerns regarding specificity, test throughput, and animal welfare, a new cell-based potency assay (CBPA) method was developed for BoNT/E drug substance and drug product; independent evaluation of this new CBPA was required. (2) Methods: The CBPA for BoNT/E is a quantitative assay that measures the accumulated cleaved SNAP25₁₈₀ in human neuroblastoma cells. It involves sequential culturing, differentiation of cells, and then treatment with drug products. Data were analyzed using a quadratic parallel model via statistical software. Linearity was determined using five effective concentration levels. Key assay parameters including accuracy, linearity, repeatability, intermediate precision and range were evaluated. (3) Results: The overall assay’s accuracy was 98%, and the intermediate precision was 6.3%. The coefficient of determination (R²) and slope were determined as 0.963 and 0.942, respectively. The root mean squared error (RMSE) was 0.057, and the intercept was 0.032 for the combined data. The repeatability was 2.4%, which is well within the acceptance criterion of ≤8%. (4) Conclusions: The evaluation was carried out within a single laboratory under controlled conditions; the new CBPA meets all acceptance criteria and can be used for BoNT/E potency determination. Full article

Streptococcus suis is an important zoonotic pathogen responsible for severe infections in pigs and humans. Its capacity to survive within phagocytic cells is considered a key virulence mechanism that contributes to dissemination and persistence in host tissues. This study employed comparative proteomic profiling to investigate intracellular adaptation of S. suis serotypes 2 (SS2) and 14 (SS14) during infection of human U937 macrophages. Five isolates originating from humans and pigs were analyzed using gel electrophoresis with liquid chromatography–tandem mass spectrometry (GeLC–MS/MS), revealing 118 differentially expressed proteins grouped into 11 functional categories. Translation-related proteins represented the largest group (48%), including upregulated ribosomal subunits (30S: S2, S5, S7, S8, S12, S15; 50S: L1, L5, L18, L22, L24, L33, L35) and translation factors such as GidA/TrmFO and RimP. Enrichment of carbohydrate metabolism and DNA replication proteins, including phosphoenolpyruvate carboxylase (PEP), UDP-N-acetylglucosamine pyrophosphorylase (GlmU), and ATP-dependent DNA helicase RuvB, indicated metabolic reprogramming and stress adaptation under intracellular conditions. Stress-response proteins such as molecular chaperone DnaK were also induced, supporting their multifunctional, “moonlighting” roles in virulence and host interaction. Comparative analysis showed that SS2 expressed a broader range of adaptive proteins than SS14, consistent with its higher virulence potential. These findings reveal conserved intracellular responses centered on translation, energy metabolism, and stress tolerance, which enable S. suis to survive within human macrophages. Integration of these intracellular proteomic signatures with previous exoproteomic, peptidomic, and network-based studies highlights translational and metabolic proteins—particularly DnaK, enolase, elongation factor EF-Tu, and GlmU—as multifunctional candidates linking survival and immunogenicity. This work establishes a comparative proteomic foundation for understanding S. suis intracellular adaptation and highlights potential targets for future vaccine or therapeutic development against this zoonotic pathogen. Full article

Bacterial resistance in foodborne pathogens is a global concern and has stimulated the search for alternative compounds to antimicrobials. In this context, the prevention of colonization by Salmonella spp. in poultry production is particularly important. This study investigated the bactericidal effect of lysozyme on Salmonella Heidelberg and Salmonella Minnesota. A total of 44 serotyped isolates were subjected to minimum inhibitory concentration (MIC) testing against 17 distinct antibiotics. Subsequently, the same isolates were subjected to minimal bactericidal concentration (MBC) with lysozyme at concentrations ranging from 15 to 2000 ppm. One strain of S. Heidelberg was selected for an in vivo challenge. Seventy-two male chicks were randomly divided into three experimental groups, and two of them were challenged on the second day with 0.5 mL of an inoculum containing 1 × 10⁵ CFU/mL. One of these groups was treated with lysozyme at a concentration of 1000 ppm per bird for 21 days. MIC tests showed that the multidrug resistance rate was 97.72%, with susceptibility only to fosfomycin, florfenicol, and meropenem. After the in vitro exposure of these isolates to lysozyme, 86.36% were inhibited at concentrations ≤ 15 ppm. The in vivo tests showed a significant reduction in the total number of chickens colonized by S. Heidelberg at 2, 5, 7, 14, 18, and 21 days of farming. On the day of slaughter, the percentage of positive birds in the inoculated group was 63.63%, while that in the group treated with lysozyme was 26.08%. These data highlight the potential use of lysozyme as an alternative to antibiotics in poultry production. Full article

Erysipelothrix rhusiopathiae is a small Gram-positive rod causing erysipelas in many animal species and humans. In poultry, disease which takes an acute form with high mortality is noted mostly in turkey, hen, and goo se flocks. Especially in geese, erysipelas cause high economic losses. In this study, we determined the phenotypic and genotypic features of Erysipelothrix strains isolated from diseased geese, using the API Coryne tests for biochemical characteristics and PCR, random amplified polymorphic DNA-PCR (RAPD) and pulsed-field gel electrophoresis (PFGE) for genetic characteristics. The isolates were confirmed with PCR to be E. rhusiopathiae and belonged to serotypes 1b, 2, and 5 with 1b serotype domination (55.3%). Among 47 isolates, five RAPD profiles (marked as A–E) and 7 PFGE profiles (marked I–VII) were noted. The RAPD profiles contained four to six bands and the PFGE profiles nine to eleven bands. The most common RAPD profile was B profile (42.5%), and the most common PFGE profile was I (36.2%). Five biochemical types of E. rhusipathiae were identified with the most common biochemical type (pyrrolidonyl arylamidase, acetyl-b-glucosaminidase, glucose, ribose, lactose- positive), which included 68.1% isolates and was matched to E. rhusiopathiae in 99.9%. Differences in biochemical reactions among the strains were related to the ability to degrade pyrazinamidase, alkaline phosphatase, and ribose. This study shows that most E. rhusiopathiae strains isolated from geese differ in their phenotypic and molecular characteristics, and there are no distinctive features that are typical of strains from geese. Full article

Dengue fever has become a major global public health challenge due to its rapidly in-creasing incidence. Rapid on-site detection of dengue virus (DENV) is critical for early diagnosis, timely patient isolation, and outbreak control. In this study, dengue virus serotype 2 (DENV-2), the predominant strain circulating in tropical and subtropical regions, was selected as the target pathogen. We established a one-tube rapid detection assay that integrates the HUDSON nucleic acid extraction-free protocol, reverse transcription recombinase-aided amplification (RT-RAA), and CRISPR/Cas12a-mediated trans cleavage activity. The method achieved a detection limit of 1 × 10² copies/μL for simulated infected samples and exhibited no cross-reactivity with other DENV serotypes (DENV-1, DENV-3, DENV-4) or with other arboviruses, including Zika, Japanese encephalitis, yellow fever, and chikungunya viruses. The assay demonstrated high sensitivity and specificity across various sample types, including mosquitoes, rodents, blood, and cultured cells, with results consistent with quantitative PCR (qPCR). Requiring only basic equipment such as a water bath, the system enables on-site detection of DENV-2 within 1 h. This simple, cost-effective, and reliable assay provides a practical tool for field-based DENV-2 surveillance and supports effective public health responses in resource-limited settings. Full article

This study assessed the epidemiological and microbiological invasive pneumococcal disease (IPD) changes that occurred before and after the emergence of COVID-19 in Italy. All IPD cases reported through the nationwide surveillance system during 2018–2023 were included. IPD incidence and serotype distributions were analyzed by age group. IPD incidence in 2020–2021 declined in all age groups compared with 2018–2019, especially in children less than 2 years of age and elderly people aged > 64 years. A resurgence of IPD cases was observed from late 2022 onwards, with values in children exceeding those seen before the pandemic. The post COVID-19 increase in children was mainly driven by some PCV13 serotypes, such as 3, 19A, and 19F, but also non-vaccine serotypes, including 10A, 8, and 24F, while in the elderly population, a predominance of serotypes 3 and 8 was observed. In conclusion, a steep drop in IPD incidence was observed during the peak of the COVID-19 pandemic, followed by a subsequent upsurge of cases, especially in children. Continuous national surveillance is necessary to monitor the dynamics and evolution of IPD and the impact of new higher-valency vaccines in Italy over the next few years. Full article

(1) Background: Salmonella are zoonotic pathogens, and rising antimicrobial resistance (AMR) amplifies their public health impact. Asymptomatic horses can act as reservoirs, contributing to environmental contamination and interspecies transmission. This study aimed to estimate the prevalence of Salmonella and characterize AMR patterns in healthy horses from eastern Spain. (2) Methods: Faecal samples from 95 asymptomatic horses were collected once daily over five consecutive days (475 samples in total) and processed under for Salmonella detection. Epidemiological information was obtained through owner questionnaires, and associations with Salmonella shedding were analyzed using generalized linear models. Antimicrobial susceptibility was assessed by minimum inhibitory concentration assays following the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. (3) Results:Salmonella was detected in 25.3% of horses (24/95), with S. Enteritidis, S. Johannesburg, and S. Virchow as the most frequent serotypes. A significant association was observed between proximity of manure storage and bacterial detection (p < 0.001). Among 24 isolates of Salmonella, 88.9% were resistant to at least one antimicrobial, and 50% exhibited multidrug resistance. The highest resistance rates were against sulfamethoxazole and gentamicin, followed by ciprofloxacin and tigecycline. (4) Conclusions: Healthy horses can act as silent carriers of multidrug-resistant Salmonella, highlighting the need for surveillance, strengthened biosecurity, and prudent antimicrobial use within a One Health framework. Full article