Aggressive Strains Research Articles

Isolation of a more aggressive GVI-1 genotype strain HX of the avian infectious bronchitis virus

The avian infectious bronchitis virus (IBV) poses a significant economic threat to the global poultry industry. Although in recent years, the GVI-1 lineage of IBV has proliferated throughout China, there is still a lack of comprehensive studies regarding the pathogenicity of this lineage, particularly with respect to infections of the digestive tract and the antigenic characteristics of the S1 gene. In this study, we investigated the effects of infecting 14-day-old chicks with the HX strain of the GVI-1 lineage over a 14-d period postinfection. Assessment of the pathogenicity of the HX strain included clinical observations; monitoring of body weight, organ viral load, viral shedding, and gross anatomy; histopathological analysis, and bioinformatics-based antigenic characterization of the S1 protein. The findings revealed that compared with previously reported GVI-1 lineage strains, the HX strain is characterized by greater virulence, with infection leading to approximately 26% mortality and extensive severe organ damage, including that of the proventriculus and kidneys. Moreover, at 14 d postinfection, 80% of oral swabs and 100% of cloacal swabs from chickens infected with the HX strain tested positive, indicating a prolonged period of viral shedding relative to that previously reported for GVI-1 lineage strains. Bioinformatic analysis of B-cell epitopes on the S1 protein revealed 7 potential antigenic epitopes. Collectively, our findings in this study provide clear evidence to indicate that compared previously reported GVI-1 lineage strains, chicks infected with the IBV GVI-1 lineage strain HX are characterized by heightened rates of mortality, more pronounced organ damage, and an extended period of viral shedding. This comprehensive characterization highlights the pathogenic potential of the GVI-1 lineage and its capacity to induce severe kidney and proventriculus damage, thereby emphasizing the imperative of early initiated preventive measures. Furthermore, on the basis of our analysis of the antigenic properties of the S1 protein, we have identified 7 potential linear B-cell epitopes, which will provide valuable insights for the development of epitope-based vaccines.

РОДОВОЙ СОСТАВ И АГРЕССИВНОСТЬ ГРИБНЫХ БОЛЕЗНЕЙ У ОДНОЛЕТНИХ ЦВЕТОЧНЫХ КУЛЬТУР

In the context of the development of the agro-industrial complex and the replacement of imported plant material in the Russian Federation, the development of methods and technologies for the prevention and control of diseases and pests is a priority area of agrarian science. Fungal diseases cause great damage to both vegetable and ornamental crops. Some of the most harmful phytopathogens are fungi of the genus Fusarium (Fusarium Link). The objective of the study is to identify and determine the aggressiveness of the pathogenic mycobiota complex present on annual flowering plants of the Lamiaceae Bromhead family. During immunological studies on plants, fungal pathogens from the genera Alternaria Nees, Fusarium Link, some species of Pythium spp. and representatives of lower mold fungi Penicillium Link, Mucor Fresen were identified. Based on this, a collection of the most common pathogens from the genera Alternaria (5 samples) and Fusarium (10 samples) was created. When testing the selected samples using the method of L.M. Sokolova, the strains of alternariosis did not show high pathogenicity, the damage score of the tested material was from 0.5 to 1.0. When testing the strains of fusarium, the damage score varied from 1.0 to 4.0. Based on this, only one aggressive strain FAK-7 was selected, which had a damage score of 4.0 for the tested material. This pathogenic strain was isolated from the root system of the snapdragon selection line A-5-1. This strain will be involved in the selection process to work on the resistance of snapdragon lines and varieties to root rot.

Trend in the age mortality structure during the COVID-19 pandemic

Introduction. The COVID-19 pandemic, caused by a novel SARS-CoV-2 coronavirus infection, lasted just over three years. Its end was announced in early May 2023. According to official data, the pandemic claimed 6.9 million lives worldwide, but it is believed that at least 20 million people were victims. The first wave of the pandemic was caused by a virus that spread from China. The virus mainly kills representatives of older age groups of the population and is characterized by a high degree of mutagenicity, which contributes to the emergence of new strains of the virus. The most aggressive and established in the population new strains of the virus spread and gave rise to the second wave of the pandemic, which turned out to be the longest. The third wave was caused by the most aggressive strain, spreading from India, and caused the greatest number of deaths. Aim of the study was to identify the extent to which changes in the virus itself affected the gender and age mortality structure during the three waves of the COVID-19 pandemic observed between 2020 and 2021. Materials and methods. The method of single factor analysis of variance was applied. The study was based on the data of the Operational Headquarters under the Government of Samara region, which were published daily with the indication of gender, age, and cause of each death. Results. The analysis confirmed the influence of the virus variability factor on the age mortality structure at the significance level of p<0.05. Comparison of the diagrams of the shares of the selected age segments in the mortality of men and women in each of the pandemic waves clearly showed how the gender and age mortality structure changed. The result of the analysis of variance showed that the changes occurring in the virus itself, although not as significant, affected the mortality pattern, with male mortality being more affected than female mortality. Conclusion. The result of the analysis of variance showed changes occurring in the virus itself to have an impact on the mortality structure, and on male mortality to a greater extent than on female mortality.

The adult plant resistance (APR) genes Yr18, Yr29 and Yr46 in spring wheat showed significant effect against important yellow rust races under North-West European field conditions

Yellow rust caused by Puccinia striiformis f. sp. tritici (Pst) is one of the most important wheat diseases. Adult plant resistance (APR) genes have gained the attention of breeders and scientists because they show higher durability compared to major race-specific genes. Here, we determined the effect of the APR genes Yr18, Yr29 and Yr46 in North-West European field conditions against three currently important Pst races. We used three pairs of sibling wheat lines developed at CIMMYT, which consisted of a line with the functional resistance gene and a sibling with its non-functional allele. All APR genes showed significant effects against the Pst races Warrior and Warrior (–), and a race of the highly aggressive strain PstS2. The effects of Yr18 and Yr46 were especially substantial in slowing down disease progress. This effect was apparent in both Denmark, where susceptible controls reached 100 percent disease severity, and in United Kingdom where disease pressure was lower. We further validated field results by quantifying fungal biomass in leaf samples and by micro-phenotyping of samples collected during early disease development. Microscopic image analyses using deep learning allowed us to quantify separately the APR effects on leaf colonization and pustule formation. Our results show that the three APR genes can be used in breeding yellow rust resistant varieties of spring wheat to be grown in North-West European conditions, and that deep learning image analysis can be an effective method to quantify effects of APR on colonisation and pustule formation.

Exploring the genetic basis of resistance to Neopestalotiopsis species in strawberry.

Aggressive strains of Neopestalotiopsis sp. have recently emerged as devastating pathogens of strawberry (Fragaria × ananassa Duchesne ex Rozier), infecting nearly all plant parts and causing severe outbreaks of leaf spot and fruit rot in Florida and globally. The development of host resistance is imperative due to the absence of fungicides that effectively inhibit Neopestalotiopsis sp. growth on an infected strawberry crop. Here, we analyzed 1578 individuals from the University of Florida's (UF) strawberry breeding program to identify and dissect genetic variation for resistance to Neopestalotiopsis sp. and to explore the feasibility of genomic selection. We found that less than 12% of elite UF germplasm exhibited resistance, with narrow-sense heritability estimates ranging from 0.28 to 0.69. Through genome-wide association studies (GWAS), we identified two loci accounting for 7%-16% of phenotypic variance across four trials and 3 years. Several candidate genes encoding pattern recognition receptors, intra-cellular nucleotide-binding leucine-rich repeats, and downstream components of plant defense pathways co-localized with the Neopestalotiopsis sp. resistance loci. Interestingly, favorable alleles at the largest-effect locus were rare in elite UF material and had previously been unintentionally introduced from an exotic cultivar. The array-based markers and candidate genes described herein provide the foundation for targeting this locus through marker-assisted selection. The predictive abilities of genomic selection models, with and without explicitly modeling peak GWAS markers as fixed effects, ranged between 0.25 and 0.59, suggesting that genomic selection holds promise for enhancing resistance to Neopestalotiopsis sp. in strawberry.

Central amygdala is related to the reduction of aggressive behavior by monosodium glutamate ingestion during the period of development in an ADHD model rat.

Monosodium glutamate (MSG), an umami substance, stimulates the gut-brain axis communication via gut umami receptors and the subsequent vagus nerves. However, the brain mechanism underlying the effect of MSG ingestion during the developmental period on aggression has not yet been clarified. We first tried to establish new experimental conditions to be more appropriate for detailed analysis of the brain, and then investigated the effects of MSG ingestion on aggressive behavior during the developmental stage of an ADHD rat model. Long-Evans, WKY/Izm, SHR/Izm, and SHR-SP/Ezo were individually housed from postnatal day 25 for 5 weeks. Post-weaning social isolation (PWSI) was given to escalate aggressive behavior. The resident-intruder test, that is conducted during the subjective night, was used for a detailed analysis of aggression, including the frequency, duration, and latency of anogenital sniffing, aggressive grooming, and attack behavior. Immunohistochemistry of c-Fos expression was conducted in all strains to predict potential aggression-related brain areas. Finally, the most aggressive strain, SHR/Izm, a known model of attention-deficit hyperactivity disorder (ADHD), was used to investigate the effect of MSG ingestion (60 mM solution) on aggression, followed by c-Fos immunostaining in aggression-related areas. Bilateral subdiaphragmatic vagotomy was performed to verify the importance of gut-brain interactions in the effect of MSG. The resident intruder test revealed that SHR/Izm rats were the most aggressive among the four strains for all aggression parameters tested. SHR/Izm rats also showed the highest number of c-Fos + cells in aggression-related brain areas, including the central amygdala (CeA). MSG ingestion significantly decreased the frequency and duration of aggressive grooming and attack behavior and increased the latency of attack behavior. Furthermore, MSG administration successfully increased c-Fos positive cell number in the intermediate nucleus of the solitary tract (iNTS), a terminal of the gastrointestinal sensory afferent fiber of the vagus nerve, and modulated c-Fos positive cells in the CeA. Interestingly, vagotomy diminished the MSG effects on aggression and c-Fos expression in the iNTS and CeA. MSG ingestion decreased PWSI-induced aggression in SHR/Izm, which was mediated by the vagus nerve related to the stimulation of iNTS and modulation of CeA activity.

SSR‐based analysis of structural variation of the Russian population of Puccinia striiformis f. sp. tritici in 2019–2021

AbstractThe importance of monitoring and management of yellow rust, caused by Puccinia striiformis f. sp. tritici (Pst), has markedly increased in Russia over recent years because of intensifying negative effects of this destructive disease on wheat production. The Pst virulence survey was conducted in 2019–2021 in the European (North‐West, Volga, North Caucasus) and Asian (Siberia) parts of Russia, and the same 109 isolates have been genotyped here with 20 SSR markers. Fifty‐three multilocus genotypes (MLGs) were detected, seven of which occurred in two or more regions. The most frequent MLG was found in three European Pst collections (except Dagestan) and Siberia. SSR‐based variation within the regional collections was low because many MLGs were closely related. Nevertheless, each collection contained relatively different small genotype groups. No clear geographic structure of the Russian Pst population was observed because the five studied regional collections shared groups of similar genotypes. The most singular SSR genotype was identified in the North‐West collection, but genotypes of four invasive isolates belonging to the PstS2 temperature‐adapted aggressive strain did not considerably differ from others. The observed heterozygosity at all SSR loci exceeded the expected one in all regional Pst collections, which could imply asexual reproduction of the pathogen. Both the SSR and virulence analyses demonstrated similar patterns of relationships between the regional Pst collections, although the magnitude of differences between the collections was larger for virulence pathotypes. However, no significant association was established between the virulence pathotypes and SSR genotypes because multiple pathotypes had the same genotype and vice versa.

Structural Characterization of Toxoplasma gondii Brain Cysts in a Model of Reactivated Toxoplasmosis Using Computational Image Analysis

Toxoplasma gondii is an obligate intracellular parasite existing in three infectious life stages—tachyzoites, bradyzoites, and sporozoites. Rupture of tissue cysts and re-conversion of bradyzoites to tachyzoites leads to reactivated toxoplasmosis (RT) in an immunocompromised host. The aim of this study was to apply ImageJ software for analysis of T. gondii brain cysts obtained from a newly established in vivo model of RT. Mice chronically infected with T. gondii (BGD1 and BGD26 strains) were treated with cyclophosphamide and hydrocortisone (experimental group—EG) or left untreated as infection controls (ICs). RT in mice was confirmed by qPCR (PCR+); mice remaining chronically infected were PCR−. A total of 90 images of cysts were analyzed for fractal dimension (FD), lacunarity (L), diameter (D), circularity (C), and packing density (PD). Circularity was significantly higher in PCR+ compared to IC mice (p < 0.05 for BGD1, p < 0.001 for the BGD26 strain). A significant negative correlation between D and PD was observed only in IC for the BGD1 strain (ρ = −0.384, p = 0.048), while fractal parameters were stable. Significantly higher D, C, and PD and lower lacunarity, L, were noticed in the BGD1 compared to the more aggressive BGD26 strain. In conclusion, these results demonstrate the complexity of structural alterations of T. gondii cysts in an immunocompromised host and emphasize the application potential of ImageJ in the experimental models of toxoplasmosis.

Diversity of Strains in the Pseudomonas syringae Complex Causing Bacterial Stem Blight of Alfalfa (Medicago sativa) in the United States.

Alfalfa growers in the Intermountain West of the United States have recently seen an increased incidence in bacterial stem blight (BSB), which can result in significant herbage yield losses from the first harvest. BSB has been attributed to Pseudomonas syringae pv. syringae and P. viridiflava; however, little is known about the genetic diversity and pathogenicity of these bacteria or their interaction with alfalfa plants. Here, we present a comprehensive phylogenetic and phenotypic analysis of P. syringae and P. viridiflava strains causing BSB on alfalfa. A multilocus sequence analysis found that they grouped exclusively with P. syringae PG2b and P. viridiflava PG7a. Alfalfa symptoms caused by both bacterial groups were indistinguishable, although there was a large range in mean disease scores for individual strains. Overall, PG2b strains incited significantly greater disease scores than those caused by PG7a strains. Inoculated plants showed browning in the xylem and collapse of epidermal and pith parenchyma cells. Inoculation with a mixture of PG2b and PG7a strains did not result in synergistic activity. The populations of PG2b and PG7a strains were genetically diverse within their clades and did not group by location or haplotype. The PG2b strains had genes for production of the phytotoxin coronatine, which is unusual in PG2b strains. The results indicate that both pathogens are well established on alfalfa across a wide geographic range and that a recent introduction or evolution of more aggressive strains as the basis for emergence of the disease is unlikely.

Identificación de fuentes de resistencia a <i>Fusarium oxysporum</i> en genotipos de <i>Physalis </i>sp.

The resistance of Cape gooseberry to Fusarium oxysporum was evaluated in 70 accessions of Physalis peruviana and related taxa (P. philadelphica, P. ixocarpa, P. floridana, P. pubescens, P. angulata, P. pruinosa, P. viscosa, P. mexicana, Nicandra physalodes, and Solanum auriculatum). These accessions were obtained from different national and international collections, including accessions from the Colombian productive sector. These represented wild materials, commercial cultivars, native and foreign weeds, and commercial ecotypes from the main producing countries: Colombia, South Africa, Kenya, and Peru. The evaluation of resistance to F. oxysporum was carried out under greenhouse conditions using the most aggressive strain supplied by the Fusarium collection maintained by the molecular microbiology laboratory of the Center for Biotechnology and Bioindustry (CBB), currently in charge of the Working Collection of Microorganisms of Agrosavia, which was isolated from infected fields. The symptoms were monitored using a severity scale, containing 10 degrees and five categories. Data information obtained from daily evaluations was analyzed through a severity evaluation and different statistical analyses. The results identified one accession belonging to Physalis peruviana and two related taxa (Physalis floridana and Solanum auriculatum) as resistant to this pathogen. These accessions could be directly used in breeding programs, either as improved cultivars or as race-specific resistance donors for other Physalis peruviana genotypes.

Flavescence Dorée Strain-Specific Impact on Phenolic Metabolism Dynamics in Grapevine (Vitis vinifera) throughout the Development of Phytoplasma Infection.

Flavescence dorée phytoplasma (FDp) is a phytopathogenic bacterium associated with Grapevine yellowS disease, which causes heavy damage to viticultural production. Epidemiological data revealed that some FDp strains appear to be more widespread and aggressive. However, there is no data on mechanisms underlying the variable pathogenicity among strains. In this research, we employed chromatographic and spectrophotometric techniques to assess how two strains of FDp influence the levels of grapevine phenolic compounds, which are frequently utilized as indicative markers of stress conditions. The results pointed to the upregulation of all branches of phenolic metabolism through the development of infection, correlating with the increase in antioxidative capacity. The more aggressive strain M54 induced stronger downregulation of phenolics' accumulation at the beginning and higher upregulation by the end of the season than the less aggressive M38 strain. These findings reveal potential targets of FDp effectors and provide the first functional demonstration of variable pathogenicity between FDp strains, suggesting the need for future comparative genomic analyses of FDp strains as an important factor in exploring the management possibilities of FDp.

Biochemical Evidence for a Pathological Variant of Progressive Supranuclear Palsy

AbstractBackgroundTau proteins aggregate into spatially and morphologically distinct lesions in primary and secondary tauopathies. These signature lesions result from deposition of tau proteins that are distinctly modified via missense mutation and/or post‐translational modification for each disease strain. Identifying the unique tau protein abnormalities that lead to specific neurodegenerative diseases is beneficial in their early diagnosis and treatment. This is especially true for Progressive Supranuclear Palsy a primary tauopathy with clinical symptoms mirroring Parkinsonian syndromes and frontotemporal dementias.MethodBiochemical analysis of tau aggregates from patients with a pathological diagnosis of Progressive Supranuclear Palsy (n = 60) demonstrate that the tau protein modifications observed in this disease result from tau that is specifically modified and thereby forms the basis of the distinct disease strains observed. Here data collected using the sarkosyl‐insoluble tau fractions from tissue samples of pathologically diagnosed patients with Progressive Supranuclear Palsy without comorbidities allows for the direct observation of the modifications. Most interesting is the variability of the tau proteins that actually accumulate for this disease opening up the possibility that tau strains may exist within any given tauopathy even as the clinical manifestations appear similar. This indicates that early and specific identification and detection of these strains is critical for the development of therapies for these diseases.ResultExtraction and examination of sarkosyl‐insoluble tau proteins from deceased patients pathologically diagnosed with Progressive Supranuclear Palsy indicate that multiple tau strains exist within this primary tauopathy. Western blotting of these extracts from patient tissues demonstrates a unique banding pattern of insoluble tau in a subset of the cases that exhibit extreme hyperphosphorylation as indicated by additional high molecular weight tau banding. These patients also had an earlier age of onset and age of death indicating a more aggressive disease strain. Additional data is presented comparing the structure and seeding capability of this insoluble tau and the distribution and burden of insoluble tau in these Progressive Supranuclear Palsy patients compared to those with typical onset and insoluble tau signature.ConclusionMultiple pathological tau strains exist in Progressive Supranuclear Palsy.

A rabbit model of ear otitis established using the Malassezia pachydermatis strain C23 from dogs.

Fungal infections are a growing problem for both humans and animals due to the emergence of pathogenic strains resistant to modern antifungal treatments. To evaluate the efficacy of new antifungal drugs, it is essential to develop animal models that demonstrate typical responses to both the infection (pathogenesis and clinical course) and to the treatment, including adverse effects. In this study, we established a rabbit otitis model by infection of an aggressive multidrug-resistant strain from dogs, Malassezia pachydermatis C23, with no need for concomitant immunosuppression. Twenty healthy adult male gray giant rabbits (1 year old, 5.5 kg) were inoculated once with M. pachydermatis C23 at 108 colony-forming units/mL. We observed the clinical signs of the disease and collected ear smears and blood samples every 5 days. The infection progressed rapidly and exhibited characteristic clinical signs without spontaneous recovery for at least 1 month. In fact, substantial deterioration was observed as evidenced by blood parameters. This rabbit otitis model established using an aggressive drug-resistant fungus strain without immunosuppression could prove valuable for testing novel antifungal agents.

Priming corn resistance to Goss’s wilt using a weakly aggressive strain of Clavibacter nebraskensis

Goss’s wilt, caused by the gram-positive bacterium Clavibacter nebraskensis, has become one of the most widely spread corn diseases in the USA and Canada. Considered as a relatively new disease, with limited knowledge about the more recently renamed pathogen causing it is, it is today a serious yield-limiting factor in corn crops in North America. The diversity of C. nebraskensis strains translates into the differential plant responses it causes, ranging from hypersensitive-like response to partial resistance, or otherwise susceptibility expressed as dark, water-soaked spots and shiny patches of dried bacterial ooze on the lesions. Weakly aggressive strains of C. nebraskensis typically appear as the season winds down and the crop is about to be harvested, whereas highly aggressive strains can be found at any point during the growing season. Previous research showed that plant’s ethylene and reactive oxygen species (ROS) are essential in limiting the spread of Goss's wilt symptoms near infection sites by triggering programmed cell death (PCD). Preliminary observations that certain strains induce strong defense responses with very little to no symptoms fed the idea to use them for disease resistance priming. The induction of biosynthetic or responsive genes of ethylene, ROS, and salicylic acid (SA) both at the local and distal tissues is in line with the limited disease symptoms development in response to priming with the weakly aggressive strain before further inoculation with a highly aggressive one. The results further expand our understanding of differential host responses to strains with different levels of aggressiveness. The priming process led to an inhibition of the elongated lesions in the susceptible corn plants in comparison with the unprimed plants. The expression patters of a lectin receptor-like kinase, Salt Intolerance 2 (ZmSIT2), and blue copper binding protein (ZmBCP) suggests them as key mediators of ethylene and ROS homeostasis in corn tissues upon infection. This adds to the pool of knowledge on corn defenses against bacterial pathogens and the mechanism of its biopriming, which could serve as an environment-friendly alternative method to control Goss’s wilt.

Biological and Chemical Characterization of Musa paradisiaca Leachate.

There is a growing demand for molecules of natural origin for biocontrol and biostimulation, given the current trend away from synthetic chemical products. Leachates extracted from plantain stems were obtained after biodegradation of the plant material. To characterize the leachate, quantitative determinations of nitrogen, carbon, phosphorus, and cations (K+, Ca2+, Mg2+, Na+), Q2/4, Q2/6, and Q4/6 absorbance ratios, and metabolomic analysis were carried out. The potential role of plantain leachates as fungicide, elicitor of plant defense, and/or plant biostimulant was evaluated by agar well diffusion method, phenotypic, molecular, and imaging approaches. The plant extracts induced a slight inhibition of fungal growth of an aggressive strain of Colletotrichum gloeosporioides, which causes anthracnose. Organic compounds such as cinnamic, ellagic, quinic, and fulvic acids and indole alkaloid such as ellipticine, along with some minerals such as potassium, calcium, and phosphorus, may be responsible for the inhibition of fungal growth. In addition, jasmonic, benzoic, and salicylic acids, which are known to play a role in plant defense and as biostimulants in tomato, were detected in leachate extract. Indeed, foliar application of banana leachate induced overexpression of LOXD, PPOD, and Worky70-80 genes, which are involved in phenylpropanoid metabolism, jasmonic acid biosynthesis, and salicylic acid metabolism, respectively. Leachate also activated root growth in tomato seedlings. However, the main impact of the leachate was observed on mature plants, where it caused a reduction in leaf area and fresh weight, the remodeling of stem cell wall glycopolymers, and an increase in the expression of proline dehydrogenase.

Maize plant expresses SWEET transporters differently when interacting with Trichoderma asperellum and Fusarium verticillioides, two fungi with different lifestyles.

Most Trichoderma species are beneficial fungi that promote plant growth and resistance, while Fusarium genera cause several crop damages. During the plant-fungi interaction there is a competition for sugars in both lifestyles. Here we analyzed the plant growth promotion and biocontrol activity of T. asperellum against F. verticillioides and the effect of both fungi on the expression of the maize diffusional sugar transporters, the SWEETs. The biocontrol activity was done in two ways, the first was by observing the growth capacity of both fungus in a dual culture. The second one by analyzing the infection symptoms, the chlorophyl content and the transcript levels of defense genes determined by qPCR in plants with different developmental stages primed with T. asperellum conidia and challenged with F. verticillioides. In a dual culture, T. asperellum showed antagonist activity against F. verticillioides. In the primed plants a delay in the infection disease was observed, they sustained chlorophyll content even after the infection, and displayed upregulated defense-related genes. Additionally, the T. asperellum primed plants had longer stems than the nonprimed plants. SWEETs transcript levels were analyzed by qPCR in plants primed with either fungus. Both fungi affect the transcript levels of several maize sugar transporters differently. T. asperellum increases the expression of six SWEETs on leaves and two at the roots and causes a higher exudation of sucrose, glucose, and fructose at the roots. On the contrary, F. verticillioides reduces the expression of the SWEETs on the leaves, and more severely when a more aggressive strain is in the plant. Our results suggest that the plant is able to recognize the lifestyle of the fungi and respond accordingly by changing the expression of several genes, including the SWEETs, to establish a new sugar flux.

Genetic epidemiology of late blight in Australia using ancient DNA

Late blight caused by Phytophthora infestans is the most destructive disease of potatoes worldwide and is most notable as the cause of the Irish potato famine of the mid 1840’s. Whole mitochondrial genome sequences were generated from 44 Australian, two UK and one US isolates of P. infestans stored as either herbarium specimens or as recent samples on FTA cards, spanning the period 1873–2019. Mitochondrial (mt) genome sequence comparison confirmed that over the past c. 110 years, an old A1 strain of P. infestans has been present in Australia. There was evidence, however, that P. infestans had been introduced on multiple separate occasions in the early 1900s prior to the introduction of quarantine measures. The 44 Australian samples included six infected specimens of the Australian native kangaroo apple (Solanum aviculare) collected in 1911. The P. infestans mt genome sequences from these isolates clustered with P. infestans from infected potatoes collected in Victoria (1910, 1911, 1986, 1989), South Australia (1909, 2003) and Tasmania (1910, 2019), supporting the hypothesis that Australia has one old strain that has survived since the first arrival of the pathogen into the country. The study highlights the success of Australia’s potato biosecurity setting and supports the need for ongoing surveillance and biosecurity measures to prevent the introduction of the newer more aggressive strains of the pathogen.

#4245 CATHETER-ASSOCIATED BLOODSTREAM INFECTIONS IN A HOSPITAL DIALYSIS UNIT – SEASONAL INFLUENCE AND COVID-19 PANDEMIC

Abstract Background and Aims Catheter-associated bloodstream infections (CRBSI) are an important source of morbidity and mortality among patients receiving hemodialysis through a central venous catheter (CVC). Despite of the efforts to choose the arteriovenous fistula as the first vascular access, a large proportion of end stage kidney disease population initiates dialysis using these catheters. Thus, efforts to prevent catheter-associated bloodstream infections remain important. The aim of our study is to analyze the outcomes of the episodes of CRBSI in our dialysis unit. Secondly, we evaluated the seasonal distribution and the possible impact of infection-control measures implemented during COVID-19 pandemic. Method We conducted a single-center retrospective observational study of all cases of tunneled dialysis catheter-associated bacteremia that need hospitalization during a nine-year period (January 2013 – December 2022). Results A total of 67 episodes of catheter-associated bloodstream infections in 52 hemodialysis patients were registered. This translates into a total of 2 episodes per 1000 catheter-days. Among all patients, the mean age was 68.5 years, 74.6% were men and 25.4% women. Five patients (9.6%) had any type of immunosuppressive treatment. Nearly 88% used a tunneled jugular catheter as definite vascular access and the remainder used a femoral one. Eighteen of all episodes (26.9%) occurred during the first thirty days of catheter implantation. Ten of all patients (19.2%) suffer at least a second infection during the follow-up period, without differences in clinical and demographic characteristics. The microbial etiology of the infections were Gram-positive organisms in 67.2% and, within these, 83% were Staphylococcus Aureus. The catheter had to be removed in 65.7% of all cases and there were significant difference (p<0.01) between Gram negative infections (preservation of 70%, successfully treated with prolonged antibiotic therapy) and Gram positive ones (preservation 12%, 3 cases of S. epidermidis and 2 cases of S. Aureus due to limited vascular tree). Admission to the intensive care unit was required in five patients and there were only two cases of endocarditis as metastasic complication. There was no death related to CRBSI. About the seasonal distribution, the majority of episodes occurs in summer and spring (43.3% and 23.9% respectively), whereas in autumn and winter there were fewer cases registered (16.4% and 16.4% in both). Despite of the increasing use of CVC as definite vascular access in our dialysis unit (almost 60%), the rate of CRBSI has been declining in parallel over the years. Since 2018, we reported less than 0.5 episodes per 1000 catheter-days. Conclusion This study shows a low frequency of CRBSI compared to previous studies. Among all episodes, the predominant infecting organism was methicillin-sensitive Staphylococcus Aureus (14.7% were methicillin-resistant). The early catheter removal, especially in aggressive strains as S. Aureus, reflects a low number of serious complications, with uncommon metastatic infections and no death directly related to CRBSI. A large proportion of infections were in summer; it may be attributable to hiring of less experienced professionals. We identified a substantial decline in rates of CRBSI coincident with COVID-19 pandemic. Nevertheless, this reduction was apparent beginning nearly two years before pandemic. This suggests that factors other than changes in infection-control practices during the pandemic are partially responsible of that.

Focus Issue Articles on Diagnostic Assay Development and Validation: The Science of Getting It Right

Focus Issue Articles on Diagnostic Assay Development and Validation: The Science of Getting It Right

Сохранение агрессивности штаммов грибов из рода Fusarium, поражающих подсолнечник, в культуре на разных субстратах и температурных режимах

Species of a genus Fusarium Link. are the most spread fungi infecting agricultural crops including sunflower. Breeding for the resistance promotes the decrease in spreading and development of diseases but to choose breeding material it is necessary to use the most aggressive strains of pathogen. The purpose of the research was to conduct a comparative analysis of preserving of aggressiveness of strains of two species from the genus Fusarium infecting sunflower in a clear culture on the different vegetal substrates. The object of the research was species F. sporotrichioides Sherb. and F. oxysporum (Schlecht.) Snyd. et Hans. var. orthoceras (Appl. et Wr.) Bilai, isolated from the sunflower roots infected with fusariosis. There is presented a range of variability of these strains aggressiveness at preserving temperature +4 °C and +22–28 °C on sterile sunflower seeds, husks, and fragments of plants du ring five months. When preserving the strains of both species at a temperature of +22–28 °C on seeds the significant decrease of the aggressiveness was stated on the third month and on husks – on the forth one. At lowered temperature of +4 °C the aggressiveness of F. sporotrichioides was decreasing insignificantly on sunflower stems and husks during five months, the important decrease of the aggressiveness of F. oxysporum var. orthoceras was stated on the fourth month. We estimated the more aggressive species F. sporotrichioides preserve the high aggressiveness during longer time (five month) than F. oxysporum var. orthoceras.