Microbiology spectrum最新文献

Current vaccine research still confronts multiple challenges, and epitope-focused vaccine design serves as an effective technical approach to address these issues. Antigens harbor multiple epitopes; however, the number of epitopes capable of triggering significant antibody responses in vaccinated individuals remains undefined. This study aimed to determine the number of non-overlapping epitopes-designated "effective epitopes" hereafter-that trigger significant antibody production in vaccinated individuals when presented in distinct PlpE epitope-chimeric proteins. Herein, chimeric proteins incorporating varying numbers of PlpE non-overlapping B-cell epitopes were generated. By analyzing serum antibody responses in vaccinated individuals, we defined the quantitative characteristic of PlpE-derived effective epitopes. The total number of PlpE effective epitopes in vaccinated individuals was 2.6 (95% CI: 1.909-3.201) for full-length PlpE and 1.2 (95% CI: 0.5426-1.857), 0.9 (95% CI: 0-1.820), and 0.2 (95% CI: 0-0.5016) for the PlpE chimeric proteins (PlpE-VP60P, PlpE-BcfA, PlpE-PtfA), respectively. With an increase in the number of PlpE non-overlapping epitopes incorporated into the chimeric proteins, the number of PlpE effective epitopes exhibited a trend of initial increase followed by a decrease. Ultimately, the average total number of effective epitopes across all PlpE chimeric proteins did not exceed 3, with the highest number 2.1 (95%CI: 1.572-2.628). In conclusion, the number of PlpE non-overlapping epitopes on an antigen, that trigger significant antibody responses in each vaccinated individual, is very limited.IMPORTANCEEpitopes underpin the antigenicity of protein antigens. Although the concept of antigenic epitopes has been proposed over 50 years, our understanding on epitopes remains incomplete. Multiple antigenic epitopes can be identified on a single antigen, while the number of these epitopes that function in vaccinated individuals remains unclear-a gap hindering the rational design of vaccines. In previous studies, we identified six non-overlapping epitopes of Pasteurella multocida PlpE. Herein, we found that the total number of non-overlapping epitopes-capable of significantly triggering antibody production-that are present in PlpE chimeric proteins does not exceed three per vaccinated individual. This finding offers important insights for rational vaccine design: given the highly limited number of non-overlapping epitopes that function in vaccinated individuals, only a limited number of epitopes can be grafted onto scaffold proteins. Epitope-focused vaccine design must, therefore, account for competitive interactions between epitopes on the new antigen.

Interferon-γ release assays (IGRAs), such as the QuantiFERON-TB Gold Plus (QFTTB), are commonly used to detect past exposure to Mycobacterium tuberculosis complex (Mtb), the cause of tuberculosis (TB). IGRA-positive (IGRA+) asymptomatic individuals are diagnosed with presumptive latent tuberculosis infection (LTBI) and often offered therapy to prevent active disease. However, discordant results during serial testing pose challenges for interpretation and may lead to unnecessary treatment. We conducted a retrospective study of subjects who received QFTTB testing at Stony Brook Medicine between October 2020 and March 2024 to identify sociodemographic and clinical variables associated with quantitative QFTTB results. A total of 743 subjects were analyzed, including all 436 QFTTB-positive (QFTTB+) cases of 11,641 tests ordered (3.7%), of whom 16 were diagnosed with active TB during the 4-year study period within the context of a reported incidence rate of 3.4/100,000 persons per year in Suffolk County, a region of low TB incidence. A random sample of 307 age-sex-matched QFTTB-negative controls was included. Of 203 subjects undergoing serial QFTTB testing, 170 (83.7%) had concordant results, while 33 (16.3%) showed discordance-23 (69.7%) with reversion and 10 (30.3%) with conversion. Conversions occurred in significantly older subjects (mean age 51.1 ± 15.0 vs 37.0 ± 15.6, P = 0.025) and over longer intervals (415.1 vs 91.2 days, P = 0.026). Our findings reinforce the use of confirmatory or repeat testing before initiating LTBI therapy, particularly when testing intervals are short (<6 months) or results fall near the diagnostic cutoff (0.35 IU/mL).

Importance: Reliable interpretation of interferon-γ release assays (IGRAs) is critical for the diagnosis and management of latent tuberculosis infection (LTBI). However, variability in test performance during serial or confirmatory testing complicates clinical decision-making and may result in unnecessary treatment. Our study demonstrates that demographic factors, clinical comorbidities, and testing intervals contribute to discordant QuantiFERON-TB Gold Plus results. These findings underscore the need to integrate epidemiologic risk, pre-test probability of Mycobacterium tuberculosis complex exposure, clinical history, and repeat testing when appropriate before initiating LTBI therapy. Improved understanding of IGRA variability can strengthen both patient care and research applications, including tuberculosis vaccine and protective biomarker studies.

Most human pathogens, while originating from animals, have crossed species barriers to infect humans, often leading to outbreaks of new infectious diseases. Despite significant efforts, the mechanisms, timing, and locations of these emerging diseases remain largely uncertain. Here, using a viral metagenomic approach, we discovered a novel canine-associated parvovirus in human oropharyngeal secretions. Molecular screening revealed the presence of this parvovirus in different canine tissues, including 24 of 108 pharyngeal lymph node samples. Further molecular investigation showed that the virus was detected in the oropharyngeal secretions of pet dogs and in human samples that were not linked to these animals. This parvovirus was therefore named human-canine associated parvovirus 1 (HCAPV-1). Nine complete genomes of HCAPV-1 were acquired through next-generation sequencing, combining Sanger sequencing. Genomic and phylogenetic analyses indicate that these nine strains of HCAPV-1 belong to the genus Protoparvovirus and form a distinct clade, with their closest relatives being newlaviruses from foxes. Amino acid substitutions have been characterized in the capsid proteins of the variants of HCAPV-1, which potentially alter their infection patterns. Potential genomic recombination was also observed in HCAPV-1. Taken together, our findings reveal the presence of a novel parvovirus in both canine and human samples, highlighting the need to investigate its host range and transmission dynamics.IMPORTANCEThis study identified a novel parvovirus, human-canine associated parvovirus 1 (HCAPV-1), which was detected in human oropharyngeal secretions and various canine tissues, suggesting that its host range may extend beyond a single species. Phylogenetic analysis revealed that HCAPV-1 forms a distinct clade within the genus Protoparvovirus, closely related to newlaviruses from foxes. Amino acid substitutions observed in the capsid proteins of HCAPV-1 variants indicate genetic divergence, warranting further investigation into their potential implications for host interactions. Recombination events may have contributed to its emergence. This finding highlights the importance of continued surveillance in settings where humans and companion animals coexist and underscores the need for further research to clarify the ecological and host-range characteristics of such viruses.

Transmission of rifampicin-resistant and multidrug-resistant tuberculosis (MDR/RR-TB) is a major driver of the global drug-resistant TB epidemic, yet the contribution of compensatory mutations to its spread remains uncertain. We analyzed 206 non-duplicate MDR/RR-TB isolates collected from five surveillance sites in Hunan Province, China, between 2013 and 2020 using whole-genome sequencing. Transmission clusters were defined by ≤12 single-nucleotide polymorphism (SNP) differences, and compensatory mutations in rpoA, rpoB, and rpoC were identified through a curated mutation catalog and phylogenetic evidence. Clusters were further classified based on whether compensatory mutations predated transmission (C-type), arose after transmission (M-type), or were absent (N-type), with M-type clusters excluded to reduce confounding. Among the 206 isolates, 63 (30.6%) carried at least one compensatory mutation, predominantly in rpoC, and 27 clusters (32.5%) were identified, ranging from 2 to 6 isolates. No significant difference was observed in clustering frequency between compensated and non-compensated strains (21.7% vs 32.8%, P = 0.113), nor in cluster size between C-type and N-type clusters (P = 0.961). These findings demonstrate that compe nsatory mutations do not significantly affect transmission clustering at the population level; instead, prolonged infectious periods associated with diagnostic delays and treatment challenges are more likely to sustain MDR/RR-TB spread, underscoring the importance of rapid detection, timely effective therapy, and robust patient management to curb transmission.IMPORTANCEUnderstanding the drivers of multidrug-resistant and rifampicin-resistant tuberculosis (MDR/RR-TB) transmission is critical for global TB control. Compensatory mutations in RNA polymerase subunits have been proposed as key contributors to the success of drug-resistant strains, yet population-level evidence has been limited. In this population-based genomic study of 206 MDR/RR-TB isolates collected over 8 years in Hunan Province, China, we systematically examined the association between compensatory mutations and transmission clustering. Our results show that compensatory mutations did not significantly increase clustering frequency or cluster size, indicating a limited impact on the spread of MDR/RR-TB in the community. These findings challenge the prevailing assumption that compensatory evolution is a major determinant of transmission success and provide robust genomic evidence to refine our understanding of drug-resistant TB epidemiology.

Antibiotic resistance is a critical public health issue, causing resistant bacterial strains to be increasingly difficult to control. Antivirulence therapies, which target bacterial virulence factors rather than kill bacteria, present a promising approach. Sortase enzymes, particularly SrtA, are crucial for gram-positive bacterial virulence by anchoring surface proteins essential for bacterial adhesion and biofilm formation to the bacterial outer cell wall. This study evaluates the selectivity of the peptidomimetic inhibitor BzLPRDSar toward various gram-positive bacteria. The BzLPRDSar significantly inhibited biofilm formation in multidrug-resistant Staphylococcus aureus and Staphylococcus epidermidis. Conversely, it showed variable and generally lower selectivity to gram-positive species such as Enterococcus faecalis, Bacillus cereus, and Streptococcus agalactiae. The selectivity toward Staphylococcus species is attributed to conserved structural elements in the SrtA enzyme, particularly the β7/β8 loop region with a key tryptophan, likely facilitating strong binding interactions with the inhibitor.

Importance: Antibiotic resistance is making it harder to treat bacterial infections, even with our strongest medicines. This study explores a new approach that does not aim to kill bacteria but instead disarms them by blocking the tools they use to cause disease. We focused on a bacterial enzyme called sortase A (SrtA), which helps harmful bacteria stick to surfaces and form protective layers called biofilms-structures that make infections very difficult to treat. We tested a specially designed molecule, BzLPRDSar, and found it could stop biofilm formation in drug-resistant strains of Staphylococcus aureus and Staphylococcus epidermidis. It was less effective against other bacteria, likely because of differences in the SrtA enzyme sequences. Our findings suggest that targeting virulence rather than killing bacteria may offer a safer and more sustainable way to treat infections, especially those caused by bacteria that no longer respond to antibiotics.

Bacteroides thetaiotaomicron (B. theta) dominates the gut microbiome of most mammals. This strictly anaerobic gut symbiont colonizes the mucus layer of host intestinal epithelial cells in both healthy and diseased conditions. Reduced neuronal and vagal afferent innervation observed in germ-free mice was found to be normalized by colonization with B. theta. In addition to deficits in gut innervation, germ-free mice have been reported to have reduced neuronal number and neurotransmitter levels in the brain. Here, we investigated the hallmarks of Alzheimer's disease (AD) in the brain of germ-free mice compared to mice mono-colonized with B. theta. We analyzed the number of mature neurons, neurotransmitter transporters, amyloid precursor protein processing, and inflammatory status in three brain regions: the hippocampus, prefrontal cortex (PFC), and cerebellum. The hippocampus and the PFC are regions thought to be highly susceptible to pathogenesis, whereas the cerebellum is thought to be only mildly affected. Interestingly, secretion of neuroprotective sAPPα decreased in hippocampus and remained unchanged in PFC, while levels were increased in the cerebellum in response to bacterial colonization. In addition, the number of presynaptic boutons increased in the hippocampus but remained unaffected in the cerebellum.

Importance: The gut microbiome has been reported to not only contribute to diseases of the gastrointestinal tract but also to interfere with and potentially even initiate diseases of other organ systems, such as the brain. Interference with the gut microbiome has been shown to elicit cognitive changes, for example, in rodent models of AD. Colonization with the common gut microbe B. theta not only affected the brain per se in our study but also showed specific brain region-dependent effects related to AD. This implies that evaluating the impact the microbiome might have on brain disorders needs a much more detailed investigation in the future with spatial and also potentially time resolution.

Plants of the genus Terminalia have been widely used in traditional medicine for the treatment of multiple ailments, including infectious diseases. Previously, our group performed metabolomic analyses using liquid chromatography-mass spectrometry of various Terminalia spp. and highlighted several phytochemicals (particularly flavonoids) that may contribute to the antibacterial activities of those species. Herein, we screen 15 flavonoids found in Terminalia spp. against antibiotic-resistant and antibiotic-sensitive strains of Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus. Orientin, hispidulin, vitexin, rutin, fisetin, and isoorientin inhibited the growth of both methicillin- and β-lactam-resistant pathogens, producing MIC values ranging from 250 to 62.5 µg/mL. Orientin and isoorientin were the most effective at restricting the growth of methicillin-resistant and β-lactamase pathogens, with MIC values of 125 µg/mL against E. coli and extended-spectrum β-lactamase E. coli and 62.5 µg/mL against S. aureus. In combination with selected conventional antibiotics, some flavonoids potentiated the antimicrobial activity of selected conventional antibiotics. A total of 4 synergistic, 4 additive, and 22 non-interactive interactions were identified. The toxicity of the flavonoids was examined using Artemia franciscana nauplii lethality assays. With the exception of fisetin, genistein, and gossypetin, the flavonoids were non-toxic. Orientin and isoorientin were assessed for their potential to inhibit efflux pumps and demonstrated notable efflux pump inhibitory activity at four different concentrations: 125.0, 62.5, 31.25, and 15.26 µg/mL. The results obtained suggest that these flavonoids could serve as a valuable tool in combating antibiotic resistance.

Importance: Bacteria are becoming resistant to many types of antibiotics. This study has identified plant phytochemicals known as flavonoids, which were found to be capable of inhibiting the growth of numerous bacterial pathogens. Evidence is shown which reveals that the compounds are capable of blocking bacterial efflux pumps, which demonstrate that the flavonoids may be valuable compounds in the design of new antibiotic drugs.

Corn silk extract (CSE), a traditional medicinal food rich in polysaccharides, flavonoids, and saponins, has been used as a natural antihypertensive agent, but its mechanism remains unclear. This study aimed to evaluate whether CSE can lower blood pressure through gut microbiota modulation. Spontaneously hypertensive rats received oral CSE for 4 weeks, followed by a 4-week drug-free observation. The treatment significantly reduced blood pressure, increased microbial diversity, decreased the Firmicutes/Bacteroidetes ratio, and enriched beneficial genera, such as Akkermansia and Lactobacillus. These changes were accompanied by reduced serum lipopolysaccharide and pro-inflammatory cytokines, elevated nitric oxide (NO) levels, and restored endothelial function. Permutational multivariate analysis of variance (PERMANOVA) and correlation analyses showed that microbiota and inflammatory markers were more strongly associated with blood pressure improvements than urinary indices. Structural equation modeling suggested a potential mechanistic pathway involving gut microbiota-inflammation-NO regulation. Importantly, fecal microbiota transplantation using post-treatment donor samples reproduced the antihypertensive and anti-inflammatory effects, confirming the microbiota's critical mediating role. These findings provide the first experimental evidence that CSE functions as a prebiotic to improve gut microbial balance and vascular health, offering a promising natural strategy for microbiota-targeted blood pressure control.

Importance: This study identifies corn silk extract (CSE) as a novel plant-derived prebiotic with antihypertensive effects mediated through gut microbiota modulation. Using a spontaneously hypertensive rat model, we demonstrated that CSE reshapes gut microbial composition, enhances microbial diversity, and promotes beneficial genera while reducing systemic inflammation and restoring nitric oxide (NO)-mediated vascular function. Importantly, fecal microbiota transplantation confirmed the causal role of gut microbiota in mediating these effects. These findings highlight a gut microbiota-inflammation-NO axis as a key pathway through which CSE regulates blood pressure. As a safe, accessible, and food-compatible intervention, CSE represents a promising strategy for non-pharmacological blood pressure management and broadens the application scope of prebiotics in cardiovascular health.

Mycoplasma hyopneumoniae (M. hyopneumoniae, Mhp), the primary causative agent of swine enzootic pneumonia, poses significant threats to the pork industry, challenging food safety and sustainable development of the livestock industry. Here, four protoberberine alkaloids-epiberberine, jatrorrhizine, berberine, and coptisine-were identified by screening multiple natural compounds, and their anti-Mhp activity was evaluated. All alkaloids exhibited potent inhibitory effects against the virulent Mhp strain ES-2, with minimum inhibitory concentrations from 8 to 32 µg/mL. Their bactericidal activities were time- and concentration-dependent. At the cellular level, all protoberberine alkaloids significantly enhanced infected cell viability, suppressed pro-inflammatory cytokine expression (TNF-α, IL-6, and IL-1β), and exhibited low cytotoxicity toward host cells. In a Chang Da binary cross-breeding pig infection model, jatrorrhizine markedly alleviated clinical symptoms, reduced pulmonary pathogen loads, and mitigated histopathological damage in lung tissues, with therapeutic efficacy comparable to that of florfenicol. Our findings demonstrated that protoberberine alkaloids possessed potent anti-Mhp activity, high safety profiles, and promising therapeutic potential.

Importance: Swine enzootic pneumonia, caused by Mycoplasma hyopneumoniae (M. hyopneumoniae), remains one of the most economically devastating respiratory diseases in the global swine industry. The emergence of antibiotic resistance in livestock highlights the urgent need for effective, safe, and sustainable alternatives. This study demonstrates that naturally derived protoberberine alkaloids exhibit potent antibacterial activity against M. hyopneumoniae while maintaining low host cytotoxicity and strong anti-inflammatory effects. Among them, jatrorrhizine showed remarkable therapeutic efficacy in infected pigs, comparable with that of florfenicol. These findings provide a scientific basis for developing protoberberine alkaloids as promising natural alternatives to conventional antibiotics for controlling M. hyopneumoniae infections, thereby contributing to improved animal health, reduced antimicrobial resistance, and sustainable swine production.