MAJOR PATHOGENICITY FACTORS OF STREPTOCOCCUS PYOGENES

Streptococcal diseases and their complications are one of the global problems of international health. S. pyogenes (group A streptococci - GAS) is a pathogen that causes significant morbidity in different countries and different age groups of the population, occurring both sporadically and epidemic outbreaks. Due to ineffective antibacterial therapy or its absence, 3-5% of people who have had streptococcal infection may develop complications such as acute rheumatic fever, rheumatic heart disease, acute post-streptococcal glomerulonephritis and invasive complications: necrotizing fasciitis and myositis, septicemia and toxic shock syndrome, highly lethal due to the rapid development of the process and systemic organ damage. According to recent estimates, at least 517,000 deaths occur annually in the world due to diseases caused by GAS. The diverse arsenal of pathogenic factors of this pathogen is manifested in a combination of joint or sequential reactions in the process of microbial colonization of tissue, formation of the focus of infection and overcoming the host's defense mechanisms. It is an important point in the process of studying the pathogenesis of diseases caused by these microbes. The pathogenic factors of GAS can be divided into extracellular and associated with the microbial cell, predominantly with its cell wall. The spectrum activity of pathogenicity factors can be quite wide (M proteins, pyrogenic exotoxins, superantigens) or limited (serine and cysteine proteinases, streptokinase). Information about the specificity of pathogenicity factors, their properties, relationships, regulation and specific function in pathology is the task of scientific, as well as, complex researches, leading to understanding the pathogen-host interaction. An integrated approach to the investigation of GAS pathogenicity factors is needed to study the pathogenicity of streptococci, since pathogenicity factors do not manifest themselves in isolation and are not always independently regulated. In many cases, regulators control the expression of more than one of them. S. pyogenes has been studied for about 150 years but a number of issues related to their pathogenicity remain unknown to this day. Some factors need more in-depth study for example, endo--β-N-acetylglucosaminidase, argininedeiminase. Immunoglobulin-degrading enzymes require special attention due to their possible participation in the genesis of immunopathological processes of streptococcal etiology. This review summarizes the literature data about most of the pathogenicity factors of S. pyogenes and their role in the infectious process.

Virulence and pathogenicity factors of S. agalactiae strains isolated from pregnant women and newborns

BACKGROUND: Obstetric and neonatal infections caused by Steptococcus agalactiae are among the most significant perinatal infections. To date, intrapartum antibiotic prophylaxis is used to prevent the transmission of the pathogen to the child, however, the growth of antibiotic resistance and ineffectiveness of therapy against late-onset neonatal infection are its limitations. Vaccination is considered to be the most effective method for preventing diseases caused by S. agalactiae in both pregnant women and newborn babies. To identify promising vaccine targets and to develop alternative prevention approaches, it is necessary to study the virulence factors of S. agalactiae strains and their variability in the population. AIM: The aim of this study was to evaluate the variability of virulence and pathogenicity factors (capsular polysaccharides, pili, hypervirulent sequence type ST-17, biofilm-forming ability, antibiotic resistance) of S. agalactiae isolated from pregnant women and newborn infants in St. Petersburg, Russia. MATERIALS AND METHODS: We studied isolates of S. agalactiae out of clinical material samples obtained from pregnant women and newborns at the D.O. Ott Research Institute of Obstetrics, Gynecology, and Reproductology in 2018-2020. The PCR method was used to determine the types of capsular polysaccharides, pili, and strain affiliation with the hypervirulent sequencing type ST-17. Biofilm-forming ability was determined by the Christensen method. The antibiotic sensitivity was determined by disc diffusion. RESULTS: We examined 60 clinical isolates of S. agalactiae. The most common S. agalactiae serotypes were Ia, Ib, II, III, IV, and V; in total, these six serotypes accounted for 95.1% of all strains. The most common pili genotype was PI-1 + PI-2a (60%). Resistance to erythromycin was found in 36.7% of the strains, and a similar number of the strains were resistant to clindamycin. The ability to form biofilms was detected in 68% of the strains, and the increased ability was associated with the PI-2b pili allele. CONCLUSIONS: A hexavalent vaccine based on capsular polysaccharides of types Ia, Ib, II, III, IV, and V would have a 95% efficacy in this region. Stable distribution of different pili types is an important factor when using pili as vaccine targets. The high level of resistance of S. agalactiae strains to erythromycin and clindamycin indicates that isolates should be tested for sensitivity to these antibiotics before their use, and regular regional monitoring of antibiotic resistance of the pathogen to update clinical guidelines should be performed.

Genome-wide analysis of Claviceps paspali: insights into the secretome of the main species causing ergot disease in Paspalum spp

Background The phytopatogen Claviceps paspali is the causal agent of Ergot disease in Paspalum spp., which includes highly productive forage grasses such as P. dilatatum. This disease impacts dairy and beef production by affecting seed quality and producing mycotoxins that can affect performance in feeding animals. The molecular basis of pathogenicity of C. paspali remains unknown, which makes it more difficult to find solutions for this problem. Secreted proteins are related to fungi virulence and can manipulate plant immunity acting on different subcellular localizations. Therefore, identifying and characterizing secreted proteins in phytopathogenic fungi will provide a better understanding of how they overcome host defense and cause disease. The aim of this work is to analyze the whole genome sequences of three C. paspali isolates to obtain a comparative genome characterization based on possible secreted proteins and pathogenicity factors present in their genome. In planta RNA-seq analysis at an early stage of the interaction of C. paspali with P. dilatatum stigmas was also conducted in order to determine possible secreted proteins expressed in the infection process. Results C. paspali isolates had compact genomes and secretome which accounted for 4.6–4.9% of the predicted proteomes. More than 50% of the predicted secretome had no homology to known proteins. RNA-Seq revealed that three protein-coding genes predicted as secreted have mayor expression changes during 1 dpi vs 4 dpi. Also, three of the first 10 highly expressed genes in both time points were predicted as effector-like. CAZyme-like proteins were found in the predicted secretome and the most abundant family could be associated to pectine degradation. Based on this, pectine could be a main component affected by the cell wall degrading enzymes of C. paspali. Conclusions Based on predictions from DNA sequence and RNA-seq, unique probable secreted proteins and probable pathogenicity factors were identified in C. paspali isolates. This information opens new avenues in the study of the biology of this fungus and how it modulates the interaction with its host. Knowledge of the diversity of the secretome and putative pathogenicity genes should facilitate future research in disease management of Claviceps spp.

In Vitro Secretome Analysis Suggests Differential Pathogenic Mechanisms between Fusarium oxysporum f. sp. cubense Race 1 and Race 4

Banana Fusarium wilt, caused by the fungus pathogen Fusarium oxysporum f. sp. cubense (Foc), is a devastating disease that causes tremendous reductions in banana yield worldwide. Secreted proteins can act as pathogenicity factors and play important roles in the Foc–banana interactions. In this study, a shotgun-based proteomic approach was employed to characterize and compare the secretomes of Foc1 and Foc4 upon banana extract treatment, which detected 1183 Foc1 and 2450 Foc4 proteins. Comprehensive in silico analyses further identified 447 Foc1 and 433 Foc4 proteins in the classical and non-classical secretion pathways, while the remaining proteins might be secreted through currently unknown mechanisms. Further analyses showed that the secretomes of Foc1 and Foc4 are similar in their overall functional characteristics and share largely conserved repertoires of CAZymes and effectors. However, we also identified a number of potentially important pathogenicity factors that are differentially present in Foc1 and Foc4, which may contribute to their different pathogenicity against banana hosts. Furthermore, our quantitative PCR analysis revealed that genes encoding secreted pathogenicity factors differ significantly between Foc1 and Foc4 in their expression regulation in response to banana extract treatment. To our knowledge, this is the first experimental secretome analysis that focused on the pathogenicity mechanism in different Foc races. The results of this study provide useful resources for further exploration of the complicated pathogenicity mechanisms in Foc.

Comparative Genomic Analysis Uncovered Evolution of Pathogenicity Factors, Horizontal Gene Transfer Events, and Heavy Metal Resistance Traits in Citrus Canker Bacterium Xanthomonas citri subsp. citri

Background: Worldwide citrus production is severely threatened by Asiatic citrus canker which is caused by the proteobacterium Xanthomonas citri subsp. citri. Foliar sprays of copper-based bactericides are frequently used to control plant bacterial diseases. Despite the sequencing of many X. citri strains, the genome diversity and distribution of genes responsible for metal resistance in X. citri subsp. citri strains from orchards with different management practices in Taiwan are not well understood.Results: The genomes of three X. citri subsp. citri strains including one copper-resistant strain collected from farms with different management regimes in Taiwan were sequenced by Illumina and Nanopore sequencing and assembled into complete circular chromosomes and plasmids. CRISPR spoligotyping and phylogenomic analysis indicated that the three strains were located in the same phylogenetic lineages and shared ∼3,000 core-genes with published X. citri subsp. citri strains. These strains differed mainly in the CRISPR repeats and pathogenicity-related plasmid-borne transcription activator-like effector (TALE)-encoding pthA genes. The copper-resistant strain has a unique, large copper resistance plasmid due to an unusual ∼40 kbp inverted repeat. Each repeat contains a complete set of the gene cluster responsible for copper and heavy metal resistance. Conversely, the copper sensitive strains carry no metal resistance genes in the plasmid. Through comparative analysis, the origin and evolution of the metal resistance clusters was resolved.Conclusion: Chromosomes remained constant among three strains collected in Taiwan, but plasmids likely played an important role in maintaining pathogenicity and developing bacterial fitness in the field. The evolution of pathogenicity factors and horizontal gene transfer events were observed in the three strains. These data suggest that agricultural management practices could be a potential trigger for the evolution of citrus canker pathogens. The decrease in the number of CRISPR repeats and pthA genes might be the result of adaptation to a less stressful environment. The metal resistance genes in the copper resistant X. citri strain likely originated from the Mauritian strain not the local copper-resistant X. euvesicatoria strain. This study highlights the importance of plasmids as ‘vehicles’ for exchanging genetic elements between plant pathogenic bacteria and contributing to bacterial adaptation to the environment.

Retrotransposons as pathogenicity factors of the plant pathogenic fungus Botrytis cinerea

Background Retrotransposons are genetic elements inducing mutations in all domains of life. Despite their detrimental effect, retrotransposons can become temporarily active during epigenetic reprogramming and cellular stress response, which may accelerate host genome evolution. In fungal pathogens, a positive role has been attributed to retrotransposons when shaping genome architecture and expression of genes encoding pathogenicity factors; thus, retrotransposons are known to influence pathogenicity. Results We uncover a hitherto unknown role of fungal retrotransposons as being pathogenicity factors, themselves. The aggressive fungal plant pathogen, Botrytis cinerea, is known to deliver some long-terminal repeat (LTR) deriving regulatory trans-species small RNAs (BcsRNAs) into plant cells to suppress host gene expression for infection. We find that naturally occurring, less aggressive B. cinerea strains possess considerably lower copy numbers of LTR retrotransposons and had lost retrotransposon BcsRNA production. Using a transgenic proof-of-concept approach, we reconstitute retrotransposon expression in a BcsRNA-lacking B. cinerea strain, which results in enhanced aggressiveness in a retrotransposon and BcsRNA expression-dependent manner. Moreover, retrotransposon expression in B. cinerea leads to suppression of plant defence-related genes during infection. Conclusions We propose that retrotransposons are pathogenicity factors that manipulate host plant gene expression by encoding trans-species BcsRNAs. Taken together, the novelty that retrotransposons are pathogenicity factors will have a broad impact on studies of host-microbe interactions and pathology.

SANITARY AND ECOLOGICAL IMPORTANCE OF BACTERIA OF THE GENUS ACINETOBACTER ISOLATED FROM WATER AND FISH IN VOLGA DELTA

The article highlights the study of the sanitary and ecological features of acinetobac-teria,which were isolated from the water and fish in the Volga Delta in the period from 1987 up to 2010. Today, these bacteria are among the most dangerous pathogens for people, especially in hospitals. They can exist in hydroecosystems and interact with aquatic biota. There were analyzed 96 beluga species; 295 sturgeon species; 217 stellate sturgeon species; 50 sterlet species; 173 carp species; 447 zander species; 638 water samples in the fishing areas. There were examined the fish, parenchymal organs, intestines, gills, blood, gonads (in sturgeon), and muscle tissues. Pathogenicity factors were taken into account: growth at 37°C, fermentation of hemolysin, protease, lecithinase, catalase; viability in 3.0; 7.0; 10.0% broth with NaCl. It is shown that the occurrence of Acinetobacter in water ranged from 3.0 to 16.7%; in fish-from 4.6 to 10.5% of samples of the entire isolated microflora. Inferior to the dominant enterobacteria and aeromonads, acinetobacteria isolated from water and fish had all the analyzed pathogenicity factors, especially catalase activity. In combination with halophilicity, these bacteria can be preserved in fish when stored frozen and as salted fish products.

Coagulase-positive staphylococci in dogs and their antimicrobial resistance (systematic review)

Staphylococcus spp. a common genus of bacteria that colonizes the body of dogs. Some families of this genus are pathogenic and are involved in the development of diseases of various systems and organs, especially the skin and outer ear. One of the main signs of the most pathogenic families of this genus is the secretion of the enzyme coagulase. They are grouped into the group of coagulase-positive Staphylococcus (CoPS). S. pseudintermedius most often is isolated from a dog, about 10-60% isolates. S. aureus is identified less frequently, in 4-15% of cases, but it is associated with people who are its natural carriers. S. schleiferi subsp. coagulans is another family that can be identified in the pathological material obtained from dogs. However, coagulase is one of much different pathogenicity factors in this family. Also, microorganisms of this family can exist both in the form of a planktonic culture and in the structure of a biofilm, on which the effect of antibacterial agents is weakened. Some strain of CoPS carry genes of resistance to various antibacterial agents and may occupy a dominant position in the pathogenic process. Such strains can colonize the environment in places where animals congregate, which leads, for example, to the occurrence of clinical infections. Also resistant are strains of this family that can colonize other animals or humans. Owners and specialists working with animals are constantly at risk. To date, the issue of the emergence of resistance to beta-lactam antibiotics (methicelin-resistant strains) and the acquisition of resistance to several groups of antibacterial agents is acute. In the countries of the European Union, a fairly large number of studies are conducted aimed at studying the spread of Staphylococcus spp. analysis of virulence and pathogenicity factors, as well as mechanisms of acquiring antibacterial resistance. Programs to control the prevalence of resistant strains are also being developed there. Different authors show resistance to a large number of antibacterial agents, the profile of antibacterial resistance may differ both within different groups and between different drugs of the same pharmaceutical group. In Ukraine, there are no systematic studies of the spread of resistant strains of microorganisms among small animals. Key words: Staphylococcus spp., S. pseudintermedius, S. aureus, S. schleiferi subsp. Coagulans, CoPS, MRSP, MRSA, antibacterial resistance, dogs.

Retrotransposons as pathogenicity factors of the plant pathogenic fungus Botrytis cinerea

BackgroundRetrotransposons are genetic elements inducing mutations in all domains of life. Despite their detrimental effect, retrotransposons become temporarily active during epigenetic reprogramming and cellular stress response, which may accelerate host genome evolution. In fungal pathogens, a positive role has been attributed to retrotransposons when shaping genome architecture and expression of genes encoding pathogenicity factors; thus, retrotransposons are known to influence pathogenicity.ResultsWe here uncovered a hitherto unknown role of fungal retrotransposons as being pathogenicity factors, themselves. Studying the aggressive fungal plant pathogen Botrytis cinerea, that is known to deliver some long-terminal repeat (LTR) deriving regulatory trans-species small RNAs (BcsRNAs) into plant cells to suppress host gene expression for infection we found that naturally occurring, less aggressive B. cinerea strains possess considerably lower copy numbers of LTR retrotransposons and had lost retrotransposon BcsRNA production. By a transgenic proof-of-concept approach, we reconstituted retrotransposon expression in a BcsRNA-lacking B. cinerea strain, which resulted in enhanced aggressiveness in a retrotransposon and BcsRNA expression-dependent manner. Moreover, retrotransposon expression in B. cinerea led to suppression of plant defence-related genes during infection.ConclusionsWe propose that retrotransposons are pathogenicity factors that manipulate host plant gene expression by encoding trans-species BcsRNAs. Taken together, the novelty that retrotransposons are pathogenicity factors will have general impact on studies of host-microbe interactions and pathology.

Special Issue “Interplay between Fungal Pathogens and Harvested Crops and Fruits”

The interplay between fungal pathogens and harvest crops is important in determining the extent of food losses following the storage and transport of crops to consumers. The specific factors modulating the activation of colonization are of key importance to determining the initiation of fungal colonization and host losses. It is clear nowadays from the wide number of transcription studies in colonized fruits that pathogenicity in postharvest produce is not only the result of activation of fungal pathogenicity factors but is significantly contributed to fruit maturity and ripening. In this editorial summary of the Special Issue “Interplay between Fungal Pathogens and Harvested Crops and Fruits”, we present a short summary of future research directions on the importance of the interplay between fruit and pathogens and nine published papers (one review and eight original research papers), covering a wide range of subjects within the mechanism of pathogenicity by postharvest pathogens, including transcriptome analysis of pathogenesis, pathogenicity factors, new antifungal compounds and food toxin occurrence by pathogens. This summary may lead the reader to understand the key factors modulating pathogenicity in fruits.