Virulence Factors Research Articles

Molecular analysis of rhizobacteria with insecticidal activity against potato pest Tecia solanivora

ABSTRACT Rhizosphere bacteria, selected by plants for their diverse beneficial functions, have the potential to act as biocontrol agents due to their capability to infect and kill insect pests. One such pest, Tecia solanivora, poses a significant threat to potato crops in Central and South America. However, the capacity of rhizobacteria from potato crops to control T. solanivora remains unclear. This study aimed to evaluate the insecticidal capabilities of rhizobacteria against T. solanivora. Through phenotypic assays and genomic analysis, the virulence factors employed by the rhizobacteria in the infection process were characterised. Two rhizobacteria strains, Enterobacter asburiae, and Raoultella terrigena, exhibited significant insecticidal activity, causing 85% and 77% larval mortality, respectively. Genomic analysis revealed numerous virulence factors in both strains, including enzymes, antimicrobial compounds, volatile organic compounds, and toxins, which contribute to rhizosphere colonisation and the infection and killing of insect pests. Notably, the Tc toxin in E. asburiae and the SdiA receptor in R. terrigena were identified as the most significant virulence factors in these rhizobacteria. Comparative genomics showed that the virulence factors identified in this study are common among known insecticidal rhizobacteria, such as Yersinia entomophaga MH96 and various strains of Pseudomonas. These findings elucidate the infection mechanisms employed by R. terrigena and E. asburiae against T. solanivora, highlighting their potential as biocontrol agents for this pest.

Avian pathogenic Escherichia coli (APEC) isolated from chicks and embryos in the hatchery.

Avian pathogenic Escherichia coli (APEC) is the most common cause of omphalitis. This disease affects newborn chicks up to the 7th day of life, causing high mortality and reduced performance of broilers. The study aimed to determine the frequency of APEC occurrence in embryos and newly hatched chicks. E. coli isolates were subjected to PCR to identify the minimal predictive virulence factors, phylogenetic groups, and predictive identification of the clonal complex (CC) ST131, ST117, and ST95. The phenotypic analysis assessed the antimicrobial resistance profile. A total of 254 samples were analyzed and 60.63% (n = 154/254) were positive for E. coli, of which 35.71% (n = 55/154) were classified as APEC (60% (n = 33/55) isolated in the yolk sac of day-old chicks, 29.09% (n = 16/55) in pipped eggs and 10.91% (n = 6/55) in embryonated eggs). The B2 phylogenetic group accounted for 21.81% (n = 12/55), with an increase in the contamination by B2 strains during the incubation process, from 6.25% (n = 1) to 30.30% (n = 10). We also identified 14.54% (n = 8/55) strains for the G group. The sequence types ST131 and ST117 were observed at the same frequency (10.90%, n = 6), followed by ST95 (3.6%, n = 2). A total of 27.27% were considered multidrug-resistant strains (MDR). The highest resistance rate was amoxicillin (43.64%, n = 24) and tetracycline (25.45%, n = 14). To a lesser extent, levels of resistance to critical drugs commonly used in hatcheries were identified, such as ceftiofur (20%, n = 11) and gentamicin (7%, n = 4).

Inhibitors of the PqsR Quorum-Sensing Receptor Reveal Differential Roles for PqsE and RhlI in Control of Phenazine Production.

Pseudomonas aeruginosa is a leading cause of hospital-acquired infections and it is resistant to many current antibiotic therapies, making development of new antimicrobial treatments imperative. The cell-to-cell communication process called quorum sensing controls P. aeruginosa pathogenicity. Quorum sensing relies on the production, release, and group-wide detection of extracellular signal molecules called autoinducers. Quorum sensing enables bacteria to synchronize group behaviors. P. aeruginosa possesses multiple quorum-sensing systems that control overlapping regulons, including some required for virulence and biofilm formation. Interventions that target P. aeruginosa quorum-sensing receptors are considered a fruitful avenue to pursue for new therapeutic advances. Here, we developed a P. aeruginosa strain that carries a bioluminescent reporter fused to a target promoter that is controlled by two P. aeruginosa quorum-sensing receptors. The receptors are PqsR, which binds and responds to the autoinducer called PQS (2-heptyl-3-hydroxy-4(1H)-quinolone) and RhlR, which binds and responds to the autoinducer called C4-HSL (C4-homoserine lactone). We used this reporter strain to screen >100,000 compounds with the aim of identifying inhibitors of either or both the PqsR and RhlR quorum-sensing receptors. We report results for 30 PqsR inhibitors from this screen. All of the identified compounds inhibit PqsR with IC50 values in the nanomolar to low micromolar range and they are readily docked into the autoinducer binding site of the PqsR crystal structure, suggesting they function competitively. The majority of hits identified are not structurally related to previously reported PqsR inhibitors. Recently, RhlR was shown to rely on the accessory protein PqsE for full function. Specifically, RhlR controls different subsets of genes depending on whether or not it is bound to PqsE, however, the consequences of differential regulation on the quorum-sensing output response have not been defined. PqsR regulates pqsE. That feature of the system enabled us to exploit our new set of PqsR inhibitors to show that RhlR requires PqsE to activate the biosynthetic genes for pyocyanin, a key P. aeruginosa virulence factor, while C4-HSL is dispensable. These results highlight the promise of inhibition of PqsR as a possible P. aeruginosa therapeutic to suppress production of factors under RhlR-PqsE control.

Genetic diversity of Streptococcus agalactiae from dairy cattle with mastitis in Argentina

BackgroundBovine mastitis is an important health problem in dairy cattle which affects the quality and yield of milk and causes significant economic losses in the dairy industry. Streptococcus agalactiae is a Gram-positive and zoonotic bacterium that causes clinical and subclinical contagious bovine mastitis. The main strategy for the control of this pathogen in dairy herds is the antimicrobial therapy. The aim of this study was to determine the genetic diversity of S. agalactiae using Multiple Locus Variable number tandem repeat -VNTR- Analysis (MLVA), serotypes, virulence factors (VF) and antimicrobial resistance (AMR) profiles and to compare the discrimination power of these different methods in strains isolated from cattle with mastitis in Argentinian dairy farms.ResultsEighty-seven S. agalactiae isolates obtained from dairy cattle with mastitis in Argentina were analyzed. The detected serotypes were III, II and Ia. The most frequent virulence and AMR detected genes were cpsA, hylB, PI-2b, cylE, rib, spb1, and tetO and ermB respectively. A total of 36 VF + AMR profiles were detected with a discriminatory power of the method of Ds = 0.96. The MLVA based on six VNTRs showed 29 profiles with a Ds = 0.90. The analysis of VF + AMR + MLVA data together showed 59 profiles with an increased discriminatory power (Ds = 0.98).ConclusionThis study highlights that the MLVA is recommended to add to other methodologies in order to study epidemiological relationships in this species Although within each dairy farm there was a predominance of certain serotypes/virulence profiles, the characteristics did not show total homogeneity, as expected due to the contagious nature of the pathogen. This suggests the incorporation of animals from other herds at some point, a practice not uncommon among dairy farms in Argentina. By other hand, the detection of a same clone in the same farm in different periods confirms that S. agalactiae strains can persist on dairy farms for a long time.

Recent Advances in the Development of Antifungal Agents: Beyond Azoles, Polyenes, and Echinocandins.

The escalating incidence of antimicrobial resistance to antifungal agents, alongside the emergence of drug-resistant fungal strains, constitutes a significant threat to a potential global fungal pandemic. In response, researchers are intensifying efforts to identify novel antifungal compounds through diverse methodologies. Emerging strategies focus on innovative therapeutic targets that may reduce the risk of resistance development while offering broad-spectrum efficacy against fungal infections. Additionally, these approaches present potential cost-effectiveness and accelerated development timelines. This review systematically categorizes a range of novel antifungal compounds, including antifungal peptides, cationic amphiphiles, small molecules, polymers, and repurposed drugs, based on their efficacy in inhibiting fungal growth and associated virulence factors. These compounds exhibit notable antimicrobial activity across in silico, in vitro, and in vivo systems against various pathogenic fungal strains, with several showing substantial promise for clinical application. Furthermore, the review highlights the limitations of standard antifungals and elucidates the mechanisms by which fungal strains develop resistance. This work aims to engage researchers in the distinctive field of fungal biology and foster the exploration of new antifungal strategies.

Staphylococcus aureus SaeR/S-regulated factors overcome human complement–mediated inhibition of aggregation to evade neutrophil killing

Staphylococcus aureus (S. aureus) is a frequent culprit in implant-associated infections and employs many virulence factors to escape killing by the host immune system. The specific immune evasion strategies used by small aggregates of S. aureus on a surface, precursors to mature biofilm, are still relatively unknown. Time-lapse confocal microscopy was leveraged to quantify interactions between S. aureus aggregates and human neutrophils in vitro and identify specific mechanisms of resistance to neutrophil killing. Surface-associated wild-type S. aureus rapidly formed small biofilm aggregates when grown in human serum. Conversely, aggregation was inhibited when the SaeR/S two-component gene regulatory system was deleted. Wild-type aggregates began to show individual and population-level resistance to neutrophil killing upon reaching sizes of approximately 50 to 75 µm2, whereas Δsae clusters failed to reach these sizes and were readily cleared. Aggregation of Δsae strains was impaired by serum complement, and this inhibition required complement proteins C3 and factor B, but not C4 or C5, suggesting that this activity primarily occurs at the level of the alternative pathway. Several complement-inhibiting genes regulated by SaeR/S were identified that collectively facilitate biofilm aggregate formation in human, but not murine serum. Finally, aggregation of two related opportunistic pathogens, Staphylococcus epidermidis and Enterococcus faecalis, was inhibited by serum. These data demonstrate a function of serum complement, the ability to inhibit bacterial aggregation, that is potently blocked by S. aureus through the production of multiple complement-interfering proteins that are regulated by the SaeR/S system.

The intricacies of Acinetobacter baumannii: a multifaceted comprehensive review of a multidrug-resistant pathogen and its clinical significance and implications

Acinetobacter baumannii, a highly adaptive and formidable nosocomial pathogen, has emerged as a symbol of modern medicine's struggle against multidrug resistance (MDR). As a Gram-negative dweller in moist hospital environments, A. baumannii has proven its ability to colonize the most vulnerable—critically ill patients—leaving behind a trail of infections highlighted by high morbidity and mortality and rendering nearly all antibiotics ineffective. This literature review aims to provide an in-depth, comprehensive overview of microbiological features, virulence factors, clinical manifestations, epidemiology, and antibiotic resistance mechanisms of A. baumannii. It also highlights the different diagnostic approaches, possible treatment strategies, and infection control, as well as the profound public health burden this pathogen imposes. The genus Acinetobacter has undergone a pivotal taxonomic journey and categorization. In addition, the intricate virulence mechanisms and factors of A. baumannii, including but not limited to outer membrane components and nutrient acquisition systems, have contributed to its pathogenicity and severe clinical manifestations ranging from respiratory tract infections and meningitis to urinary tract infections, skin infections, and bloodstream infections. This review also describes the epidemiological trend of A. baumannii established by its global prevalence and distribution, risk factors, hospital-acquired vs. community-acquired infections, and its geographical variations. In terms of antibiotic resistance, this pathogen has demonstrated resilience to a wide range of first-line and last-resort antibiotics due to its different evasion mechanisms. The current diagnostic approaches, treatment strategies, and infection control measures are further analyzed in detail, underscoring the need for prompt and precise identification of A. baumannii to guide appropriate therapy and reinforce the optimal approaches to limit its transmission and control outbreaks. Finally, the review addresses the substantial public health implications, reflecting on the hindrance that A. baumannii brings to healthcare systems, and the urgent need for global surveillance, effective infection control protocols, innovative research, and therapeutic approaches to mitigate its global threat.

Toxin-producing Escherichia coli: a long-term retrospective study in dogs and cats between 2017 and 2023 in Italy

IntroductionToxin-producing Escherichia coli are gastrointestinal agents found in both animals and humans, potentially leading to mild-to-severe pathogenic outcomes. Therefore, this study aimed to assess the prevalence of toxin-producing E. coli in owned and stray dogs and cats in Southern Italy in order to provide insights into the epidemiology of these zoonotic bacterial infections.MethodsDuring necropsy, organ swabs (i.e., intestine, liver, lung, spleen, lymph node, and brain) from dogs and cats were collected and analyzed to isolate E. coli colonies through bacterial culture between 2017 and 2023. The isolated strains were then subjected to biomolecular investigation for pathogenicity factors.ResultsOut of 911 animals, 451 (49.5%) tested positive for E. coli, including 252 (56.1%) dogs and 199 (43.1%) cats. The higher prevalence among dogs was statistical significant (p < 0.01) and associated with a higher risk of infection (OR = 1.69). However, no statistically significant difference in prevalence over the years was found (p = 0.150). At least one virulence factor was detected in 22% of animals, with 12% exhibiting pathogenicity factors (CNF, CDT, LT, and ST) and 10% showing virulence genes (vtx1, vtx2, and eae). Cats were significantly more likely to produce verocytotoxin compared to dogs (p = 0.020, OR = 2.04).DiscussionThese findings suggest a wide circulation of toxin-producing E. coli in dogs and cats in Southern Italy, highlighting the importance of routine screening for these agents to ensure animal welfare and public health.

Molecular and biological characterization of <i>Streptococcus pneumoniae</i> isolates from patients with pneumococcal meningitis

The aim of the study is to provide key characteristics of Streptococcus pneumoniae isolates circulating in Russia in 2015–2020 and isolated from pneumococcal meningitis patients based on high-throughput sequencing data, including global pneumococcal sequence clusters, serotypes, virulence factors and genetic determinants of resistance, in comparison with clinical data on antimicrobial susceptibility. Materials and methods. We studied 68 invasive S. pneumoniae isolates from blood and cerebrospinal fluid of patients with bacterial meningitis in different regions of Russia in 2015–2020. Species identification was performed taking into account the morphology of colonies on blood agar, the presence of α-hemolysis, negative catalase reaction, sensitivity to optoquine, and positive latex-agglutination results. The sensitivity of isolates to antimicrobials was determined by microdilution in broth, and sensitivity categories were determined based on borderline values of minimum inhibitory concentrations (MICs). Whole genome sequencing of S. pneumoniae isolates, analysis of isolates for penicillin-binding protein signature, determination of global pneumococcal sequence clusters, MLST alleles, serotypes, sequence types and acquired resistance genes (mefA, ermB, tetM, folA/P, cat), identification of virulence genes were carried out. Results. Twenty-eight GPSCs, 45 sequence types and 27 serotypes were identified. The coverage rates of PPV-23 and PCV-13 were 78% and 59%, respectively. Serotypes 3 (18%), 19F (9%), 23F (7%) and 15B (6%) were predominant. The GPSC12 lineage (serotype 3) was predominant (43%). Lineages expressing vaccine serotypes GPSC1(19F), GPSC6(14), GPSC13(6A), GPSC904(14) and GPSC10(19F) exhibited multiple antimicrobial resistance, including penicillin resistance. The resistant lineages expressing non-vaccine serotypes were GPSC230 (13) and GPSC177 (35F). In most cases, genotypic and phenotypic resistance to penicillin (increased MICs of β-lactams correlated with types of penicillin-binding proteins), erythromycin (ermB, mefA, ermB/mefA), clindamycin (ermB) and tetracycline (tetM), and trimethoprim-sulfamethoxazole (folA, folP) was found to be consistent. The virulence genes cbpG, lytA, pce/cbpE, pavA, pfbA, ply, hysA, nanA and cps4A were detected in all isolates. Zinc metalloproteinase C was detected in 13% of isolates. Conclusion. A high diversity of serotypes and lineages among pneumococcal isolates from meningitis patients was revealed. Out of the 68 S. pneumoniae isolates from patients with bacterial meningitis, more than 17% belonged to non-vaccine serotypes. The results of phenotypic and genotypic antimicrobial resistance comparison were characterized by good concordance, which indicates the necessity for further study of the possibility of using whole-genome sequencing as a diagnostic tool to identify resistance mechanisms in clinical isolates of pneumococci.

Prognostic Value of the Brixia Radiological Score in COVID-19 Patients: A Retrospective Study from Romania

The novel coronavirus pandemic, SARS-CoV-2, has a variable clinical spectrum, ranging from asymptomatic to critical forms. High mortality and morbidity rates have been associated with risk factors such as comorbidities, age, sex, and virulence factors specific to viral variants. Material and Methods: We retrospectively evaluated imaging characteristics using the Brixia radiological score in relation to favorable or unfavorable outcomes in adult patients. We included COVID-19 cases, admitted between 2020 and 2022, in a specialized pulmonology hospital with no intensive care unit. We analyzed 380 virologically confirmed COVID-19 cases, with a mean age of 52.8 ± 13.02 years. The mean Brixia radiological score at admission was 5.13 ± 3.56, reflecting predominantly mild-to-moderate pulmonary involvement. Multivariate analysis highlighted the utility of this score as a predictive marker for COVID-19 prognosis, with values >5 correlating with other severity biomarkers, NEWS-2 scores, and a lack of vaccination and hospitalization delay of more than 6 days from symptom onset. Summarizing, the Brixia score is itself an effective tool for screening COVID-19 cases at risk of death for early recognition of clinical deterioration and for decisions regarding appropriate care settings. Promoting vaccination can reduce the severity of radiological lesions, thereby decreasing the risk of death. Technologies based on artificial intelligence could optimize diagnosis and management decisions.

Giant transposons promote strain heterogeneity in a major fungal pathogen.

Fungal infections are difficult to prevent and treat in large part due to strain heterogeneity, which confounds diagnostic predictability. Yet, the genetic mechanisms driving strain-to-strain variation remain poorly understood. Here, we determined the extent to which Starships-giant transposons capable of mobilizing numerous fungal genes-generate genetic and phenotypic variability in the opportunistic human pathogen Aspergillus fumigatus. We analyzed 519 diverse strains, including 11 newly sequenced with long-read technology and multiple isolates of the same reference strain, to reveal 20 distinct Starships that are generating genomic heterogeneity over timescales relevant for experimental reproducibility. Starship-mobilized genes encode diverse functions, including known biofilm-related virulence factors and biosynthetic gene clusters, and many are differentially expressed during infection and antifungal exposure in a strain-specific manner. These findings support a new model of fungal evolution wherein Starships help generate variation in genome structure, gene content, and expression among fungal strains. Together, our results demonstrate that Starships are a previously hidden mechanism generating genotypic and, in turn, phenotypic heterogeneity in a major human fungal pathogen.IMPORTANCENo "one size fits all" option exists for treating fungal infections in large part due to genetic and phenotypic variability among strains. Accounting for strain heterogeneity is thus fundamental for developing efficacious treatments and strategies for safeguarding human health. Here, we report significant progress toward achieving this goal by uncovering a previously hidden mechanism generating heterogeneity in the human fungal pathogen Aspergillus fumigatus: giant transposons, called Starships, that span dozens of kilobases and mobilize fungal genes as cargo. By conducting a systematic investigation of these unusual transposons in a single fungal species, we demonstrate their contributions to population-level variation at the genome, pangenome, and transcriptome levels. The Starship compendium we develop will not only help predict variation introduced by these elements in laboratory experiments but will serve as a foundational resource for determining how Starships impact clinically relevant phenotypes, such as antifungal resistance and pathogenicity.

The Link Between Periodontal Disease and Alzheimer's Disease: a narrative review

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder influenced by a range of factors, including chronic inflammation and microbial infections. Recent research highlights a potential link between AD and periodontal disease — a chronic inflammatory condition caused by dysbiotic oral bacteria such as Porphyromonas gingivalis. These pathogens may reach the brain via the bloodstream or trigeminal nerve, triggering neuroinflammation through microglial activation and promoting pathological changes, including amyloid-β accumulation and Tau hyperphosphorylation. P. gingivalis secretes virulence factors like gingipains and lipopolysaccharides (LPS), which disrupt immune responses and contribute to neuronal damage. Genetic predispositions, such as mutations in microglia-regulating genes (e.g., TREM2, CD33, CLU), further impair immune function and exacerbate AD pathology. Aging, a common risk factor for both diseases, weakens immune defenses and the blood-brain barrier, facilitating bacterial entry into the brain. As no cure currently exists for AD, preventing and managing periodontal disease could be a promising strategy to reduce the risk and progression of AD. This review underscores the need for interdisciplinary approaches and further research into the oral-systemic connection to better understand, prevent, and treat neurodegenerative diseases like Alzheimer’s.

No Genomic Signatures Were Found in Escherichia coli Isolates from Camels With or Without Clinical Endometritis

Clinical endometritis is a leading cause of infertility in she-camels. We commonly isolate E. coli from camel uteri with and without endometritis during our routine diagnosis of conception failure. From an epidemiological standpoint, it is critical to know if certain E. coli genotypes and virulence factors are specifically associated with endometritis. Thus, we aimed to compare the abundance of virulence elements and genotypes in uterine E. coli from camels with and without endometritis and understand their evolution. For this investigation, we retrieved data from the genomes of 28 E. coli isolates from humans, cats, dogs, horses, cows, and birds and 14 sequenced genomes of camel uterine E. coli isolates. We found no specific E. coli genotype or virulence factor associated with endometritis. Instead, multiple genotypes and high genomic diversity were observed. Moreover, horizontal gene transfer driven by genomic islands and plasmids contributed to the genetic diversity of the isolates, resulting in the acquisition of virulence genes, metabolic characteristics, and antibiotic resistance determinants to trimethoprim, sulfonamide, streptomycin, and tetracycline. Additionally, the phylogenetic position of the E. coli isolates from camel uteri suggests that they originated from intestinal strains. In conclusion, there was no evidence of E. coli specialization, and E. coli alone may not be able to develop endometritis, as other factors are required. Also, we elucidated the mechanism behind the diversity of the gene repertoire of E. coli isolated from camel uteri. These findings provide insight into the evolutionary origins of E. coli isolates from camel uteri.

A Sec-Dependent Effector from “Candidatus Phytoplasma ziziphi” Suppresses Plant Immunity and Contributes to Pathogenicity

Jujube witches’ broom (JWB) disease, caused by Candidatus Phytoplasma ziziphi (Ca. P. ziziphi), severely threatens the production of Chinese jujube (Ziziphus jujuba Mill.). Emerging evidence highlights the critical role of phytoplasma-secreted effectors in pathogenesis, though few have been functionally characterized. Here, we identified a Sec-dependent effector, JWB790, from Ca. P. ziziphi, which was shown to suppress plant immunity. Through transient expression assays in Nicotiana benthamiana, pathogen inoculation assays, the generation of transgenic Arabidopsis thaliana plants, and RNA-seq-based transcriptomic profiling, we systematically investigated the virulence function of JWB790. Our findings revealed that JWB790 is highly expressed in JWB-infected tissues. The transient expression of JWB790 in N. benthamiana suppressed BAX-induced cell death and H2O2 accumulation. Furthermore, the stable overexpression of JWB790 in A. thaliana compromised disease resistance, accompanied by reduced H2O2 accumulation and callose deposition triggered by flg22. Additionally, the RNA-seq analysis of JWB790 transgenic Arabidopsis plants indicated that the overexpression of JWB790 altered the expression of biotic stress-related genes. In summary, JWB790 is a virulence factor that suppresses plant immunity and promotes pathogen proliferation. These results advance our understanding of Ca. P. ziziphi pathogenesis.

Virulence Genes Encoding for Panton Valentine Leucocidin and Toxic Shock Syndrome Toxin in Methicillin Resistant Staphylococcus aureus

Background: The outcome of Staphylococcal infections ranging from mild skin infection to fatal necrotising pneumonia is determined by the co-presence of virulence factors such as enzymes, toxins (Panton valentine leucocidin & toxic shock syndrome toxin) and methicillin resistance. In this study the association of toxin genes encoding for PVL and TSST was seen with drug resistance. Methods: Staphylococcus aureus isolates collected from clinical samples (pus, tracheal aspirate, wound swabs and blood) from inpatients of the tertiary care hospital. The isolates were analysed for presence of toxin genes and drug resistance. DNA extraction was done by boiling method and target genes were identified by PCR and gel electrophoresis. The data was analysed using Microsoft excel. Chi-square test was used for comparison of qualitative data. Unpaired t test was used for comparison of quantitative data. P value less than 0.05 was taken as significant. Results: Methicillin resistance was seen in 54.8% (108/197) of the staphylococcal isolates. There was no significant difference in MRSA and MSSA distribution amongst hospitalized or outpatients. The PVL and TSST gene was present in 123 (62.4%) and 29 (14.7%) isolates respectively. The presence of both the PVL and TSST were significantly higher in MRSA (P≤0.05). Conclusion: There was significantly higher association of virulence markers such as PVL and TSST in MRSA. The presence of toxins should be investigated from cases of non-resolving MRSA infections to initiate treatment effective against toxins for patient management.

Vaginal Candida albicans infections: host-pathogen-microbiome interactions.

Vaginal Candida albicans infections: host-pathogen-microbiome interactions.

The Magnaporthe oryzae effector Pwl2 alters HIPP43 localization to suppress host immunity.

The rice blast fungus Magnaporthe oryzae secretes a battery of effector proteins to facilitate host infection. Among these effectors, Pathogenicity toward Weeping Lovegrass 2 (Pwl2) was originally identified as a host specificity determinant for the infection of weeping lovegrass (Eragrostis curvula) and is also recognized by the barley (Hordeum vulgare) Mla3 resistance protein. However, the biological activity of Pwl2 remains unknown. Here, we showed that the Pmk1 MAP kinase regulates PWL2 expression during the cell-to-cell movement of M. oryzae at plasmodesmata-containing pit fields. Consistent with this finding, we provided evidence that Pwl2 binds to the barley heavy metal-binding isoprenylated protein HIPP43, which results in HIPP43 displacement from plasmodesmata. Transgenic barley lines overexpressing PWL2 or HIPP43 exhibit attenuated immune responses and increased disease susceptibility. In contrast, a Pwl2SNDEYWY variant which does not interact with HIPP43 fails to alter the plasmodesmata localization of HIPP43. Targeted deletion of three PWL2 copies in M. oryzae resulted in a Δpwl2 mutant showing gain of virulence toward weeping lovegrass and barley Mla3 lines, but reduced blast disease severity on susceptible host plants. Taken together, our results provide evidence that Pwl2 is a virulence factor that suppresses host immunity by perturbing the plasmodesmatal deployment of HIPP43.

A witches' broom phytoplasma effector induces stunting by stabilizing a bHLH transcription factor in Ziziphus jujuba plants.

Phytoplasmas are specialized phloem-limited bacteria that cause diseases on various crops, resulting in significant agricultural losses. This research focuses on the jujube witches' broom (JWB) phytoplasma and investigates the host-manipulating activity of the effector SJP39. We found that SJP39 directly interacts with the plant transcription factor bHLH87 in the nuclei. SJP39 stabilizes the bHLH87 homologs in Arabidopsis thaliana and jujube, leading to growth defects in the plants. Transcriptomic analysis indicates that SJP39 affects the gibberellin (GA) pathway in jujube. We further demonstrate that ZjbHLH87 regulates GA signaling as a negative regulator, and SJP39 enhances this regulation. The research offers important insights into the pathogenesis of JWB disease and identified SJP39 as a virulence factor that can contribute to the growth defects caused by JWB phytoplasma infection. These findings open new opportunities to manage JWB and other phytoplasma diseases.

Molecular identification, antibiotic susceptibility, and biofilm formation of airborne bacteria

Pathogenic bacterial communities present in urban green spaces significantly affect human health, particularly for immunocompromised populations. The diverse range of pathogenic bacteria found in these areas poses substantial management challenges because of their high prevalence of antibiotic resistance, which can be life-threatening, particularly for immunocompromised individuals, including older adults and children. This study identified airborne bacterial species from 14 natural parks in the Hail region of the Kingdom of Saudi Arabia. Bacterial colonies isolated on blood agar plates were purified and characterised based on their morphological traits and their ability to secrete various virulence factors. A total of 28 distinct airborne bacterial species were isolated and purified. Antibiotic susceptibility tests revealed high resistance to fosfomycin (41.17%), ampicillin (17.64%), tetracycline (17.64%), and gentamicin (11.76%). Biofilm formation was evaluated qualitatively by slime production and quantitatively by crystal violet technique. The results revealed that 41.17% of the tested strains were non biofilm producers on polystyrene surfaces, 17.64% were weak biofilm formers, and 23.52% exhibited moderate biofilm formation. Notably, six strains exhibited strong biofilm-forming capabilities. Additionally, two bacteria from the Arthrobacter genus (A. crystallopoietes and A. saudimassiliensis) were identified. These findings provide valuable insights into the microbial composition of natural parks in the Hail region and highlight effective management strategies to mitigate health risks.

Emergence and characterization of a ST852 Klebsiella quasipneumoniae clinical isolate coharboring blaNDM-1 and blaKPC-2 in China

ObjectivesTo characterize a rare ST852 Klebsiella quasipneumoniae strain co-producing NDM-1 and KPC-2 isolated from a clinical patient.MethodsMinimum inhibitory concentrations (MICs) were measured using a VITEK 2 compact system and broth microdilution. Conjugation experiments were conducted using film matings. Whole genome sequencing (WGS) was performed using Illumina and Nanopore platforms. Antimicrobial resistance determinants were identified using the ABRicate program in the ResFinder database. Insertion sequences (ISs) were identified using ISFinder. Bacterial virulence factors were identified using a virulence factor database (VFDB). Genome function annotation and classification were further analyzed using the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Cluster of Orthologous Groups (COG) databases. Capsular polysaccharides (KL) and lipooligosaccharides (OCL) were tested using Kleborate with the Kaptive. Multilocus sequence typing (MLST) and replicon types were identified using the Center for Genomic Epidemiology website. Prophage region analysis was performed using PHASTEST software. Conjugation-related elements were predicted using oriTfinder. The plasmid structure was visualized using Circos and similar plasmids in the public database were tracked using BacWGSTdb. A global phylogeny for the ST852 K. quasipneumoniae isolates was further performed.ResultsK. quasipneumoniae KPSY isolate was identified as ST852, with KL18 and O3/O3a. It has an extensive drug-resistant (XDR) profile. WGS analysis revealed that it contained one circular chromosome and three plasmids. The results of the COG and KEGG functional classifications showed that most of the functions were associated with metabolism. pKPSY-2 is a 239,226-bp IncU plasmid carrying the carbapenem resistance gene blaNDM-1. pKPSY-3 is a smaller plasmid belonging to the IncN-type conjugative plasmid with blaKPC-2. Importantly, oriT sequence, the T4SS region, T4CP, and relaxase were identified. Tracking of the blaKPC-2 plasmids showed they were identified in different species in different countries, including E. coli, Leclercia sp., Pantoea sp., and E. hormaechei. Global analysis data showed 13 ST852 strains were mainly isolated from China (84.62%, 11/13), and the remaining isolates were collected from Switzerland.ConclusionsThis is the first study to identify an ST852 NDM-1-KPC-2 coproducing K. quasipneumoniae clinical isolate. Surveillance is warranted, and early detection of this high-risk clone in the clinic is recommended to avoid its extensive spread.