Search Results (10,071)

In the post-antibiotic era, the Bacillus-based direct-fed beneficial microorganisms are emerging as a cornerstone for sustainable animal farming. This study aimed to screen and evaluate Bacillus strains with probiotic potential for use as feed additives. A total of 394 Bacillus strains were initially screened based on their extracellular enzyme production (cellulase, protease, and amylase) and antibacterial activities against Escherichia coli, Staphylococcus aureus, and Salmonella enterica. Two strains, Bacillus velezensis FJAT-10508 and FJAT-13563, were selected and subsequently subjected to in vitro probiotic characterization, safety assessment, and whole-genome analysis. The results demonstrated that both strains exhibited α-hemolysis, acceptable antibiotic susceptibility profiles, absence of invasion and cytotoxicity effect on the Caco-2 cells, and no mobile virulence or antibiotic resistance genes, indicating their safety as probiotic candidates. High endospore-forming efficiencies (72.4–90.8%), strong auto-aggregation (74–85%) and co-aggregation abilities (52–82%) were observed. In addition, both strains showed considerable tolerance to simulated gastrointestinal conditions, with vegetative cell and endospore survival rates of 28.33–38.33% and 85–89.67% at pH 2.0, and 38.33–43.33% and 90.33–96.33% in 0.3% bile salts, respectively. Overall, B. velezensis FJAT-10508 and FJAT-13563 demonstrated robust in vitro probiotic properties, supporting their potential application as reliable Bacillus-based feed additives. Full article

Members of the genus Brucella are bacterial pathogens of global importance, and their increasing detection in marine mammals has raised concerns for wildlife conservation and public health. In this study, we evaluated the biological and pathogenic characteristics of two Brucella sp. sequence type 27 (ST27) isolates obtained from a dwarf sperm whale (Kogia sima). We compared them with terrestrial and marine Brucella reference strains. We assessed resistance to polymyxin B and human serum complement, intracellular infection dynamics in HeLa epithelial cells, persistence in a murine model, and associated hematological and histopathological changes, and analyzed lipopolysaccharide (LPS) profiles. The Kogia isolates exhibited resistance to polymyxin B and serum complement, comparable to that of B. abortus 2308W and marine mammal Brucella strains. In HeLa cells, the isolates displayed distinct, strain-specific intracellular infection dynamics. In the murine model, both isolates persisted in the spleen and induced granulomatous lesions. However, splenic bacterial loads and histopathological scores were generally lower than those observed with B. abortus 2308W, which exhibited the highest virulence among the strains evaluated. Hematological alterations associated with Kogia isolates were also less pronounced than those induced by B. abortus 2308W, indicating an intermediate and strain-dependent virulence phenotype without evidence of enhanced virulence relative to the terrestrial reference strain. Western blot analyses showed that Brucella sp. ST27 isolates were not recognized by anti-B. abortus or anti-O-antigen monoclonal antibodies, while exhibiting a distinct recognition pattern with anti-B. canis serum, indicating differences in surface antigen composition. Comparative whole-genome analysis identified a limited number of isolate-specific variants affecting coding and intergenic regions. Collectively, these findings highlight phenotypic and genetic features of Brucella sp. ST27 from Kogia sima, which distinguishes it from other marine and terrestrial Brucella strains and supports further investigation into its biological behavior and potential public health relevance. Full article

Vaccination remains the core strategy for the prevention and control of Newcastle disease (ND). The inherent thermosensitivity of traditional Newcastle disease virus (NDV) vaccines imposes major limitations on their transportation, storage, and field application. To address these challenges, a novel liquid, thermostable, live ND vaccine was developed in the present study. Firstly, Tris/HCl buffer at near-neutral pH was identified as the optimal basic buffer system. On this basis, further screening and formulation optimization of vaccine stabilizers were conducted, and NDV strains with excellent thermal stability were used to verify the stability-conferring properties of the developed stabilizer. The results showed that the formulation composed of 0.5% gelatin, 4% trehalose, 0.1% L-glutamic acid, and 0.5% thiourea was confirmed as the optimal stabilizer for ND liquid vaccines. This formulation maintained the stable storage of the tested NDV for 12 months at 4 °C and exhibited promising stability for 30 days at 25 °C, marking a significant advancement toward development thermostable NDV vaccines that are independent of a continuous cold chain. More importantly, the liquid vaccine stored at 4 °C for 12 months still induced high levels of NDV-specific antibodies in specific pathogen-free chicks and provided 100% protective efficacy against challenge with virulent NDV. In conclusion, the liquid vaccine stabilizer developed in this study not only significantly enhanced the thermostability of the vaccine but also effectively maintained its immunogenicity, thereby providing an important theoretical basis for the research and development of liquid ND vaccines. Full article

Allium spp. (alliums) are susceptible to rot-diseases caused by pathogenic Fusarium spp., including F. proliferatum (FP) and F. oxysporum (FO), which can cause severe crop losses. A series of pathogenicity tests of four FP isolates from garlic (Allium sativum), four FO isolates from garlic and three FO isolates from onion (Allium cepa var. cepa) were conducted on garlic seedlings and cloves, onion seedlings and bulbs, and shallot (Allium cepa var. aggregatum) bulbs to determine the virulence of the isolates. A combination of PCRs and whole-genome sequencing (WGS), using ONT long-read technology, was used to identify genes encoding putative effectors. The FP isolates caused moderate to severe symptoms in garlic and contained homologues of SIX2, CRX1 and CRX2, and either SIX9 or SIX13. The FOC ex onion isolates caused severe disease symptoms in all allium species tested, while FO from garlic caused moderate to severe disease in garlic but only mild symptoms in onion and shallot. Fusarium oxysporum f. sp. cepae ex onion potentially contained homologues of SIX3, SIX5, SIX7, SIX9, SIX10, SIX12, SIX14, C5, CRX1 and CRX2. The most pathogenic FO isolate to garlic was Fo_VPRI44630 ex garlic, which contained SIX9, SIX13, C5, CRX1 and CRX2. The difference in virulence and putative effector profiles suggests evidence of host-associated differentiation, and as such, the f. sp. or race designation between FO ex garlic and FO ex onion should be investigated further. This is an important finding for future research into best management practices and breeding for disease resistance to FO and FP in garlic. Full article

Acinetobacter baumannii is a leading cause of healthcare-associated infections and is classified among the highest-priority antimicrobial-resistant pathogens. Its clinical success reflects the convergence of antimicrobial resistance (AMR) and biological traits that promote environmental persistence and transmission. Acinetobacter baumannii has undergone a remarkable transformation over the past few decades, evolving from a relatively obscure environmental bacterium into a globally recognized multidrug-resistant pathogen. Its prevalence in healthcare settings, particularly intensive care units, has made it a leading cause of ventilator-associated pneumonia, bloodstream infections, wound infections, and urinary tract infections. Beyond its antibiotic resistance, the bacterium’s ability to persist in hospital environments and adapt to host defences has amplified its clinical significance. Recent research has uncovered complex networks of virulence factors, regulatory systems, and metabolic strategies that enable A. baumannii to thrive in hostile environments and evade host immunity, providing new insights into its pathogenesis and potential therapeutic vulnerabilities. This review summarizes the main mechanisms underlying its pathogenicity, including desiccation tolerance, biofilm formation, disinfectant resistance, metal acquisition, motility, and the ability to enter viable but non-culturable states. In A. baumannii, AMR functions as a pathogenesis-adjacent trait, enhancing survival and clonal dissemination through genomic plasticity, resistance islands, efflux systems, and envelope remodeling. Key resistance pathways involve carbapenem-hydrolyzing oxacillinases, metallo-β-lactamases, permeability defects, and multidrug efflux, often coexisting within high-risk clones. From a clinical perspective, management of carbapenem-resistant strains requires accurate infection diagnosis, reliable susceptibility testing, site-specific and PK/PD-optimized therapy, and early reassessment. Overall, the success of A. baumannii reflects the integration of resistance and persistence within healthcare ecosystems, highlighting the need for coordinated strategies combining stewardship, infection control, improved diagnostics, and anti-biofilm or anti-virulence approaches. Full article

Mycoplasma pneumoniae is a significant pathogen responsible for community-acquired respiratory infections in children and adolescents, with the rising prevalence of macrolide-resistant M. pneumoniae (MRMP), particularly in Asia, presenting critical treatment challenges. Our previous study inferred that a macrolide efflux pump may contribute to macrolide resistance in M. pneumoniae in addition to the common point mutations in 23S rRNA gene. This study aimed to define the specific pump and confirm its role. Through comparative genomic analysis, we identified a candidate gene, MPN_080, encoding an ABC transporter permease, which was further characterized using phylogenetic analysis, AlphaFold-based structural modeling, and biochemical assays. Overexpression of MPN_080 from an erythromycin-resistant isolate in the erythromycin-sensitive M129 resulted in a significant increase in minimum inhibitory concentrations (MICs) from <0.125 µg/mL to 1 µg/mL, while similar overexpression of MPN_080 derived from M129 did not affect MICs. Notably, this resistance mechanism operates independently of M. pneumoniae virulence factors, as evidenced by unaltered colonization capacity in NCI-H292 cells and consistent immune response patterns across both strains. Our findings establish MPN_080 as a novel determinant of macrolide resistance functioning associated with enhanced ATPase activity. These insights into non-classical resistance mechanisms may guide future diagnostic and therapeutic strategies against MRMP. Full article

Cross-kingdom pathogenesis—human and animal pathogens colonizing and persisting in plants—is transforming our understanding of microbial ecology, food safety, and public health. This review translates incoming research that demonstrates plants as more than mute carriers to dynamic ecological interfaces where human and zoonotic pathogens, such as Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes, will adhere, internalize, and, in some cases, potentially evade host defenses. Such pathogens exploit evolutionarily conserved molecular processes like Type III secretion system 1 (TTSS), biofilm formation, quorum sensing, and small RNA-mediated immune sabotage that have allowed them to cross biological kingdom boundaries. To provide an entry point for pathogens, environmental conditions (e.g., contaminated irrigation water, manure application, wildlife access, and mechanical wounding) promote pathogen transfer to and penetration into plant tissues through stomata hydathodes above ground or roots below ground. Once inside, pathogens confront a range of plant immune responses, indigenous microbiota, and abiotic stresses such as UV radiation exposure, nutrient starvation, and osmotic fluctuations. Nonetheless, biofilm production, metabolic versatility, and virulence gene expression contribute to their persistence. Interactions with plant pathogens and microbiomes additionally shape colonization dynamics, for example, through co-survival and niche manipulation. With the acceleration of these processes due to climate change, urbanization, and intensified agriculture, cross-kingdom pathogenesis becomes a rising concern for One Health. Critical knowledge gaps, including seedborne transmission, microbiome engineering, and predictive modeling, are pointed out in the review along with emerging mitigation strategies, including point-of-care diagnostics and microbial biocontrol. In conclusion, this review advocates for interdisciplinary collaboration from microbiology, plant science, and One Health perspectives to predict and mitigate cross-kingdom threats to global food production. Full article

Methicillin-resistant S. aureus (MRSA) is listed by the World Health Organization as a priority pathogen posing a major worldwide threat to public health. Two lineages of MRSA predominate as causes of human infections in the U.S.: USA300 and USA100. Although they are most often grouped together as MRSA, these two lineages differ in pathogenetic mechanisms in important ways. The epidemic spread of these two dominant lineages has been problematic because of the multidrug-resistant profile of USA100 and the virulence of USA300, as well as their ability to adapt to both community and hospital environments. In this perspective, we examine what is currently known about their distinctive biology and the consequent differences in infections caused by these two main MRSA epidemic clones. The purpose of this perspective is to provide critical insights to the clinical microbiology community to stimulate further research to inform the design of new prevention and management strategies for MRSA. Full article

The increasing prevalence of multidrug-resistant (MDR) pathogens, particularly avian pathogenic Escherichia coli (APEC) and methicillin-resistant Staphylococcus aureus (MRSA), poses a severe threat to the breeding industry and human health. To develop novel antibiotic alternatives, we adopted a “converting virulence into therapy” strategy by leveraging the type VI secretion system (T6SS) of the APEC strain ACN17-20. Guided by the structural analysis of T6SS Protein 00145, we rationally designed a series of amphipathic α-helical polypeptides. Among them, polypeptide A7 emerged as a lead candidate, exhibiting potent broad-spectrum antibacterial activity with negligible cytotoxicity against mammalian cells. Mechanistic studies revealed that A7 exerts a rapid bactericidal effect through a dual mode of action: physical disruption of bacterial membrane integrity leading to cytoplasmic leakage, and induction of lethal oxidative stress via reactive oxygen species (ROS) accumulation. Furthermore, A7 demonstrated excellent efficacy in eradicating pre-formed bacterial biofilms, addressing the challenge of persistent infections in breeding environments. In a mouse sepsis model induced by APEC and MRSA, A7 treatment significantly improved survival rates (60–80%), reduced bacterial loads in vital organs, and attenuated the systemic cytokine storm (TNF-α and IL-1β), thereby alleviating immune-mediated tissue damage. In conclusion, this study identifies polypeptide A7 as a safe therapeutic agent with a dual mechanism of action, providing a promising strategy to combat MDR infections and reduce antibiotic dependence. Full article

Klebsiella pneumoniae has been associated with reproductive infections in equines. The detection of β-lactam resistance determinants, especially extended-spectrum β-lactamase (ESBL) genes, within genomic regions linked to horizontal gene transfer (HGT), is of a particular concern. In this study, we characterize the whole-genome sequences (WGS) of three K. pneumoniae equine isolates harboring multiple antimicrobial resistance genes. Two isolates were recovered from uterine washes of mares: one with endometritis (YAH-KPEM1) and one clinically normal (YAH-KPSE1), and a third from the feces of a diarrheic foal (YAH-KPF132). WGS was performed using the Illumina MiSeq platform, and the reads were subsequently processed through hybrid assembly in Unicycler v0.5.1. Genome annotation was completed using PROKKA v1.14.5. Strain YAH-KPEM1 was classified as ST127, whereas YAH-KPSE1 and YAH-KPF132 belonged to ST1630 and ST224, respectively. Notably, K. pneumoniae ST1630 and ST224 have not been reported before in equines. All three genomes encoded multiple antimicrobial resistance (AMR) determinants, including two encoding ESBL genes (CTX-M-15), as well as virulence factors and regions associated with HGT. Additionally, two (YAH-KPEM1 and YAH-KPSE1) isolates were found to be multidrug resistant (MDR), harboring an IncFIB(K) plasmid replicon, and another isolate, YAH-KPF132, carried an IncFII replicon. The detection of AMR and virulence genes in equine Klebsiella isolates has important clinical implications for guiding antimicrobial selection and improving treatment success. Full article

Foodborne pathogens of Enterobacteriaceae are becoming an increasing global concern, with multidrug-resistant strains posing significant risks to food safety and public health, especially in high-risk products like dairy. This research focused on isolating, biologically characterizing, and genomically profiling new bacteriophages that target key Enterobacteriaceae members as potential biocontrol agents. Eight phages were isolated from wastewater using four bacterial hosts and analyzed through transmission electron microscopy, one-step growth analysis, adsorption kinetics, host range evaluation, whole-genome sequencing, comparative genomics, phylogenetic analysis, proteomic profiling, and virion assembly pathway characterization. All eight isolates exhibited icosahedral heads with contractile tails typical of Myoviridae morphology, demonstrated broad-spectrum lytic activity against 21 bacterial strains (infectivity: 47.6–95.2%), showed high adsorption efficiencies (84.75–99.98%), and had burst sizes ranging from 11 to 166 particles per cell. Genome sizes varied from 103 to 170 kb with coding densities between 92–96%. Importantly, none contained antimicrobial resistance genes, virulence factors, or lysogeny-associated elements, confirming their strictly lytic lifestyles and favorable biosafety profiles. Phylogenetic and comparative analyses indicated mosaic genomic structures influenced by horizontal gene transfer rather than host phylogeny. These findings provide a robust biological and genomic basis for evaluating these phages as potentially safe and effective alternatives to antibiotics in controlling foodborne Enterobacteriaceae, pending further in situ validation. Full article

Background/Objectives: Cyanobacteria represent a diverse group of microorganisms capable of synthesizing a broad array of biologically active metabolites. Some of these compounds, believed to contribute to the ecological and evolutionary success of cyanobacteria, are increasingly being investigated for potential biomedical and biotechnological applications. They also hold promise in combating the growing threat of antimicrobial resistance (AMR). This screening study aimed to identify Baltic cyanobacterial strains with the potential to produce antibacterial compounds active against streptococci and mycobacteria, as well as quorum sensing inhibitors. Methods/Results: Extracts from forty-four cyanobacterial strains were tested using a broth microdilution assay. The most pronounced activity was observed for extracts derived from two Pseudanabaenaceae strains (KUCC C3 and C4), two Anabaena spp. strains (CCNP 1405 and CCNP 1406), and Aphanizomenon sp. KUCC C1. Inhibition of quorum sensing was the most frequently detected activity, with 30% of the tested extracts inhibiting violacein production in Chromobacterium violaceum ATCC 12472. Growth inhibition of Gram-positive bacteria was less common: 16% of cyanobacterial strains inhibited Streptococcus pyogenes ATCC 12344, and 11% inhibited Mycobacterium smegmatis ATCC 14468. Bioassay-guided fractionation of Aphanizomenon sp. KUCC C1, followed by LC–MS/MS analysis, revealed the presence of glycerolipids and glycolipids, including diacylglycerols (DAGs) and galactosyldiacylglycerols (MGDGs and DGDGs), as major constituents of fractions exhibiting quorum quenching activity. Conclusions: These findings highlight the potential of Baltic cyanobacteria as a source of natural compounds capable of disrupting bacterial communication and growth, offering prospects for the development of novel antimicrobial and anti-virulence agents. Full article

Klebsiella pneumoniae (K. pneumoniae) is an opportunistic and environmental mastitis pathogen prevalent in dairy herds worldwide. Owing to their genetic and genomic diversity, K. pneumoniae strains associated with bovine mastitis exhibit significant variation in virulence. Certain types of mastitis-causing K. pneumoniae strains exhibit enhanced pathogenicity and mammary adaptability, posing a serious threat to global public health. Bovine mastitis-causing K. pneumoniae strains can cause ultrastructural damage to bovine mammary epithelial cells (bMECs), leading to inflammatory injury, oxidative damage, apoptosis, pyroptosis, and immune evasion in bMECs. In this review, we summarize the prevalence, virulence genes, and pathogenic mechanisms of K. pneumoniae strains related to bovine mastitis. Given the increasing multidrug resistance of K. pneumoniae, we also outline the methods and mechanisms of phage therapy for K. pneumoniae infections, as well as future directions for treatment and prevention. These findings contribute to a deeper understanding of the population structure of mastitis-associated K. pneumoniae and provide valuable insights for future research on pathogenic mechanisms, vaccine development, and control strategies. Full article

Infectious pancreatic necrosis virus (IPNV), a member of the family Birnaviridae, is a major pathogen of farmed salmonids and an important model in fish virology. Despite its small genome, which encodes only five viral proteins, IPNV exhibits complex molecular processes that govern genome expression, replication, and particle assembly. Comprehensive descriptions of the molecular biology and replication cycle of IPNV were largely established in reviews published in the mid-1990s, whereas more recent reviews have primarily focused on virulence determinants, epidemiology, or host–virus interactions. This review provides an updated synthesis of available experimental knowledge on the molecular biology of IPNV by integrating classical and recent studies addressing virion architecture, genome organization, and the functions of viral proteins. Particular attention is given to the molecular events involved in the viral replication cycle, including virus entry, genome transcription, translation and replication in the cytoplasm, polyprotein processing by the viral protease, and the coordination between genome replication and virion assembly. When appropriate, experimental observations from the related Avibirnavirus infectious bursal disease virus are considered to provide additional context for molecular mechanisms conserved within the family Birnaviridae. Together, these studies outline the current understanding of the molecular processes governing IPNV replication and morphogenesis. Full article

Salmonella is a major cause of foodborne illness worldwide, posing significant risks to public health and food safety. This study investigated the prevalence, serovar distribution, genotypic characteristics, and antimicrobial resistance (AMR) profiles of Salmonella. A total of 2515 food samples were collected from retail markets, supermarkets, and food processing facilities, and 13,670 stool samples were obtained from sentinel hospitals across 14 cities in Liaoning. The Kruskal–Wallis test was used to compare genetic features among serovars, followed by Dunn’s post hoc test for pairwise comparisons. A total of 314 Salmonella strains were identified, with raw poultry showing the highest detection rate (28.88%) among food sources and children aged 0–6 years (3.47%) the highest among the clinical age groups. Among food samples, S. Enteritidis was the most prevalent serovar (42.6%), and it was also the most common in clinical samples (35.8%); in contrast, S. 4,[5],12:i:- was dominant in pediatric clinical cases. According to AMR analysis, 90.13% of strains were resistant to at least one antibiotic and 67.83% were multidrug-resistant (MDR), with the highest resistance to ampicillin (68.47%). Analysis revealed that S. 4,[5],12:i:- harbored the ASSuT resistance module (blaTEM-1B, aph(3″)-Ib/aph(6)-Id, sul2, tet(B)). Extensive MDR phenotypes were observed in S. Indiana and S. Kentucky, associated with abundant insertion sequences (IS) and resistance genes (ARGs), including clinically critical determinants (blaNDM-9, mcr-1.1, rmtB). The highest mean virulence factor (VF) count (111.17) was observed in S. Enteritidis, contributing to its epidemiological success. Conversely, S. Indiana and S. Kentucky, predominantly food-associated serovars, exhibited reduced virulence but served as critical AMR reservoirs. These findings highlight the epidemiological characteristics and AMR risks of Salmonella in food and clinical settings, providing critical data for food safety and clinical antimicrobial stewardship. Full article