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European Journal of Clinical... Nov 2013Streptococcus infections are still one of the important problems facing contemporary medicine. As the World Health Organization (WHO) warns, Streptococcus pneumoniae is... (Review)
Review
Streptococcus infections are still one of the important problems facing contemporary medicine. As the World Health Organization (WHO) warns, Streptococcus pneumoniae is responsible for the highest number of pneumonia cases all over the world. Despite an increasing number of pneumococcal vaccinations, incidences of disease connected to this pathogen's infection stay at the same level, which is related to a constantly increasing number of infections caused by nonvaccinal serotypes. Unfortunately, the pathogenicity of bacteria of the Streptococcus genus is also connected to species considered to be physiological flora in humans or animals and, additionally, new species exhibiting pathogenic potential have been discovered. This paper presents an opinion concerning the epidemiology of streptococci infections based on case studies and other publications devoted to this problem. It also sheds new light based on recent reports on the prevention of protective vaccinations application in the case of streptococci infections.
Topics: Global Health; Humans; Prevalence; Streptococcal Infections; Streptococcus pneumoniae; Virulence
PubMed: 24141975
DOI: 10.1007/s10096-013-1914-9 -
Annual Review of Microbiology 2000Virulence factors of pathogenic bacteria (adhesins, toxins, invasins, protein secretion systems, iron uptake systems, and others) may be encoded by particular regions of... (Review)
Review
Virulence factors of pathogenic bacteria (adhesins, toxins, invasins, protein secretion systems, iron uptake systems, and others) may be encoded by particular regions of the prokaryotic genome termed pathogenicity islands. Pathogenicity islands were first described in human pathogens of the species Escherichia coli, but have recently been found in the genomes of various pathogens of humans, animals, and plants. Pathogenicity islands comprise large genomic regions [10-200 kilobases (kb) in size] that are present on the genomes of pathogenic strains but absent from the genomes of nonpathogenic members of the same or related species. The finding that the G+C content of pathogenicity islands often differs from that of the rest of the genome, the presence of direct repeats at their ends, the association of pathogenicity islands with transfer RNA genes, the presence of integrase determinants and other mobility loci, and their genetic instability argue for the generation of pathogenicity islands by horizontal gene transfer, a process that is well known to contribute to microbial evolution. In this article we review these and other aspects of pathogenicity islands and discuss the concept that they represent a subclass of genomic islands. Genomic islands are present in the majority of genomes of pathogenic as well as nonpathogenic bacteria and may encode accessory functions which have been previously spread among bacterial populations.
Topics: Bacteria; Base Sequence; Biological Evolution; DNA, Bacterial; Genes, Bacterial; RNA, Transfer; Repetitive Sequences, Nucleic Acid; Virulence
PubMed: 11018140
DOI: 10.1146/annurev.micro.54.1.641 -
International Journal of Molecular... Jul 2020Microbial virulence factors encompass a wide range of molecules produced by pathogenic microorganisms, enhancing their ability to evade their host defenses and cause...
Microbial virulence factors encompass a wide range of molecules produced by pathogenic microorganisms, enhancing their ability to evade their host defenses and cause disease [...].
Topics: Bacteria; Humans; Virulence; Virulence Factors
PubMed: 32727013
DOI: 10.3390/ijms21155320 -
Canadian Journal of Microbiology Jul 2018The genus Aspergillus includes fungal species that cause major health issues of significant economic importance. These microorganisms are also the culprit for production... (Review)
Review
The genus Aspergillus includes fungal species that cause major health issues of significant economic importance. These microorganisms are also the culprit for production of carcinogenic aflatoxins in grain storages, contaminating crops, and economically straining the production process. Aspergillus fumigatus is a very important pathogenic species, being responsible for high human morbidity and mortality on a global basis. The prevalence of these infections in immunosuppressed individuals is on the rise, and physicians struggle with the diagnosis of these deadly pathogens. Several virulence determinants facilitate fungal invasion and evasion of the host immune response. Metabolic functions are also important for virulence and drug resistance, since they allow fungi to obtain nutrients for their own survival and growth. Following a positive diagnostic identification, mortality rates remain high due, in part, to emerging resistance to frequently used antifungal drugs. In this review, we discuss the role of the main virulence, drug target, and drug resistance determinants. We conclude with the review of new technologies being developed to treat aspergillosis. In particular, microsphere and nanoparticle delivery systems are discussed in the context of improving drug bioavailability. Aspergillus will likely continue to cause problematic infections in immunocompromised patients, so it is imperative to improve treatment options.
Topics: Antifungal Agents; Aspergillosis; Aspergillus fumigatus; Drug Resistance, Fungal; Humans; Immunocompromised Host; Nanoparticles; Virulence; Virulence Factors
PubMed: 29586541
DOI: 10.1139/cjm-2017-0749 -
Annual Review of Microbiology 2013Fusarium is a genus of filamentous fungi that contains many agronomically important plant pathogens, mycotoxin producers, and opportunistic human pathogens. Comparative... (Review)
Review
Fusarium is a genus of filamentous fungi that contains many agronomically important plant pathogens, mycotoxin producers, and opportunistic human pathogens. Comparative analyses have revealed that the Fusarium genome is compartmentalized into regions responsible for primary metabolism and reproduction (core genome), and pathogen virulence, host specialization, and possibly other functions (adaptive genome). Genes involved in virulence and host specialization are located on pathogenicity chromosomes within strains pathogenic to tomato (Fusarium oxysporum f. sp. lycopersici) and pea (Fusarium 'solani' f. sp. pisi). The experimental transfer of pathogenicity chromosomes from F. oxysporum f. sp. lycopersici into a nonpathogen transformed the latter into a tomato pathogen. Thus, horizontal transfer may explain the polyphyletic origins of host specificity within the genus. Additional genome-scale comparative and functional studies are needed to elucidate the evolution and diversity of pathogenicity mechanisms, which may help inform novel disease management strategies against fusarial pathogens.
Topics: Fungal Proteins; Fusarium; Genome, Fungal; Phylogeny; Plant Diseases; Virulence
PubMed: 24024636
DOI: 10.1146/annurev-micro-092412-155650 -
Advances in Applied Microbiology 2021Fungal pathogens now account for an unprecedented burden on human health. Like all microorganisms, these fungi must successfully forage for essential micronutrients such... (Review)
Review
Fungal pathogens now account for an unprecedented burden on human health. Like all microorganisms, these fungi must successfully forage for essential micronutrients such as zinc in order to proliferate. However, pathogenic microbes face an additional hurdle in securing zinc from their environment: the action of host nutritional immunity which strictly manipulates microbial access to this essential, but also potentially toxic trace metal. This review introduces the relevant pathogenic species and goes on to cover the molecular mechanisms of zinc uptake by human fungal pathogens. Fungi scavenge zinc from their environment via two basic mechanisms: via a family of cellular zinc importers-the ZIP transporters; and via a unique secreted zinc binding protein-the zincophore. However the genetic requirement of these systems for fungal virulence is highly species-specific. As well as zinc scarcity, potential intoxification with this heavy metal can occur and, unlike bacteria, fungi deal with environmental insult this via intraorganellar compartmentalization. Zinc availability also modulates the morphogenic behavior of a subset of pathogenic yeast species. This chapter will cover these different aspects of zinc availability on the physiology of human fungal pathogens with emphasis on the major pathogenic species Candida albicans.
Topics: Candida albicans; Humans; Micronutrients; Species Specificity; Virulence; Zinc
PubMed: 34742366
DOI: 10.1016/bs.aambs.2021.09.001 -
Microbial Pathogenesis May 2022Cryptococcus neoformans is an encapsulated fungal pathogen that causes infection in immunocompromised individuals such as HIV patients, organ transplant patients,... (Review)
Review
Cryptococcus neoformans is an encapsulated fungal pathogen that causes infection in immunocompromised individuals such as HIV patients, organ transplant patients, hematological malignancies, diabetes patients, etc. The most common invasive fungal pathogens are Candida spp., Aspergillus spp., and Cryptococcus spp. Cryptococcal meningitis has become increasingly common in immunocompromised patients resulting in a death rate of up to 90%. In low-income and middle-income countries, C. neoformans is a neglected killer in most parts of the world. It has unique and complicated virulence factors that facilitate its intracellular survival and dissemination. The initial infection, latency, or dissemination of the pathogen is determined by its specific morphological features such as capsule size, melanin pigment, biofilm development, etc. In this review, we discussed the worldwide distribution, classification of Cryptococcus spp., and a major focus on the pathogen's strategies that allow it to survive, proliferate subsequently disseminate resulting in cellular damage and treatment.
Topics: Cryptococcosis; Cryptococcus neoformans; HIV Infections; Humans; Virulence; Virulence Factors
PubMed: 35436563
DOI: 10.1016/j.micpath.2022.105521 -
Molecular Genetics and Genomics : MGG Nov 2022The current pandemic (COVID-19) has made evident the need to approach pathogenicity from a deeper and more systematic perspective that might lead to methodologies to...
The current pandemic (COVID-19) has made evident the need to approach pathogenicity from a deeper and more systematic perspective that might lead to methodologies to quickly predict new strains of microbes that could be pathogenic to humans. Here we propose as a solution a general and principled definition of pathogenicity that can be practically implemented in operational ways in a framework for characterizing and assessing the (degree of) potential pathogenicity of a microbe to a given host (e.g., a human individual) just based on DNA biomarkers, and to the point of predicting its impact on a host a priori to a meaningful degree of accuracy. The definition is based on basic biochemistry, the Gibbs free Energy of duplex formation between oligonucleotides and some deep structural properties of DNA revealed by an approximation with certain properties. We propose two operational tests based on the nearest neighbor (NN) model of the Gibbs Energy and an approximating metric (the h-distance.) Quality assessments demonstrate that these tests predict pathogenicity with an accuracy of over 80%, and sensitivity and specificity over 90%. Other tests obtained by training machine learning models on deep features extracted from DNA sequences yield scores of 90% for accuracy, 100% for sensitivity and 80% for specificity. These results hint towards the possibility of an operational, objective, and general conceptual framework for prior identification of pathogens and their impact without the cost of death or sickness in a host (e.g., humans.) Consequently, a reasonable prediction of possible pathogens might pave the way to eventually transform the way we handle and prepare for future pandemic events and mitigate the adverse impact on human health, while reducing the number of clinical trials to obtain similar results.
Topics: Humans; Virulence; COVID-19; Oligonucleotides; DNA; Biomarkers
PubMed: 36125534
DOI: 10.1007/s00438-022-01951-w -
Molecular Microbiology Mar 1997Virulence genes of pathogenic bacteria, which code for toxins, adhesins, invasins or other virulence factors, may be located on transmissible genetic elements such as... (Review)
Review
Virulence genes of pathogenic bacteria, which code for toxins, adhesins, invasins or other virulence factors, may be located on transmissible genetic elements such as transposons, plasmids or bacteriophages. In addition, such genes may be part of particular regions on the bacterial chromosomes, termed 'pathogenicity islands' (Pais). Pathogenicity islands are found in Gram-negative as well as in Gram-positive bacteria. They are present in the genome of pathogenic strains of a given species but absent or only rarely present in those of non-pathogenic variants of the same or related species. They comprise large DNA regions (up to 200 kb of DNA) and often carry more than one virulence gene, the G + C contents of which often differ from those of the remaining bacterial genome. In most cases, Pais are flanked by specific DNA sequences, such as direct repeats or insertion sequence (IS) elements. In addition, Pais of certain bacteria (e,g. uropathogenic Escherichia coli, Yersinia spp., Helicobacter pylori) have the tendency to delete with high frequencies or may undergo duplications and amplifications. Pais are often associated with tRNA loci, which may represent target sites for the chromosomal integration of these elements. Bacteriophage attachment sites and cryptic genes on Pais, which are homologous to phage integrase genes, plasmid origins of replication of IS elements, indicate that these particular genetic elements were previously able to spread among bacterial populations by horizontal gene transfer, a process known to contribute to microbial evolution.
Topics: Biological Evolution; Chromosomes; Genes, Bacterial; Gram-Negative Bacteria; Gram-Positive Bacteria; Virulence
PubMed: 9106201
DOI: 10.1046/j.1365-2958.1997.3101672.x -
Molecular Plant Pathology May 2008The term virulence has a conflicting history among plant pathologists. Here we define virulence as the degree of damage caused to a host by parasite infection, assumed... (Review)
Review
The term virulence has a conflicting history among plant pathologists. Here we define virulence as the degree of damage caused to a host by parasite infection, assumed to be negatively correlated with host fitness, and pathogenicity the qualitative capacity of a parasite to infect and cause disease on a host. Selection may act on both virulence and pathogenicity, and their change in parasite populations can drive parasite evolution and host-parasite co-evolution. Extensive theoretical analyses of the factors that shape the evolution of pathogenicity and virulence have been reported in last three decades. Experimental work has not followed the path of theoretical analyses. Plant pathologists have shown greater interest in pathogenicity than in virulence, and our understanding of the molecular basis of pathogenicity has increased enormously. However, little is known regarding the molecular basis of virulence. It has been proposed that the mechanisms of recognition of parasites by hosts will have consequences for the evolution of pathogenicity, but much experimental work is still needed to test these hypotheses. Much theoretical work has been based on evidence from cellular plant pathogens. We review here the current experimental and observational evidence on which to test theoretical hypotheses or conjectures. We compare evidence from viruses and cellular pathogens, mostly fungi and oomycetes, which differ widely in genomic complexity and in parasitism. Data on the evolution of pathogenicity and virulence from viruses and fungi show important differences, and their comparison is necessary to establish the generality of hypotheses on pathogenicity and virulence evolution.
Topics: Animals; Evolution, Molecular; Fungi; Host-Pathogen Interactions; Plant Diseases; Plant Viruses; Plants; Virulence
PubMed: 18705877
DOI: 10.1111/j.1364-3703.2007.00460.x