SEARCH · PubMed Health

Results for “Pathogen diversity”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources

PubMed1997

The rap and hor proteins of Erwinia, Serratia and Yersinia: a novel subgroup in a growing superfamily of proteins regulating diverse physiological processes in bacterial pathogens.

The enteric bacterium Serratia marcescens is an opportunistic human pathogen. The strain ATCC39006 makes the red pigment, prodigiosin (Pig), and the beta-lactam antibiotic carbapenem (Car). Mutants were isolated that were concomitantly defective for Pig and Car production. These mutants were found to have a mutation in the rap gene (Regulation of Antibiotic and Pigment). Sequence analysis of the rap gene revealed a predicted protein product showing strong homology to SlyA, originally thought to be a haemolytic virulence determinant in Salmonella typhimurium. Homologues of rap were detected in several bacterial genera, including Salmonella, Yersinia, Enterobacter, and species of the plant pathogen, Erwinia. The Erwinia hoeEr (homologue of rap) and the Yersinia horYe genes were also found to be very similar to rap and slyA. Marker exchange mutagenesis of horEr revealed that it encoded a regulatory protein controlling the production of antibiotic and exoenzyme virulence determinants in the phytopathogen, Erwinia carotovora subspecies carotovora. We have shown that these new homologues of SlyA form a highly conserved subgroup of a growing superfamily of bacterial regulatory proteins controlling diverse physiological processes in human, animal and plant pathogens.

Amino Acid Sequence↗

PubMed1984

[Significance of hemagglutinins for the pathogenicity of avian influenza viruses].

In addition to acute viral diseases, persistent infections have attained considerable interest in recent years. Such persistent infections are characterized by extended time periods in which the infecting virus remains within the organism before the eventual appearance of manifest symptoms. These infections may be evoked by a variety of virus species resulting in a diversity of pathogenic reactions and clinical manifestations. The mechanisms of viral persistence, where known, also appear to be quite diverse. As far as space permits, some examples of persistent infections will be presented and the mechanisms of the pathogenesis of the resulting diseases will be discussed.

Amino Acid Sequence↗

PubMed1999

Design of a "microbicide" for prevention of sexually transmitted diseases using "inactive" pharmaceutical excipients.

The human immunodeficiency virus (HIV-1) pandemic has been driven primarily by the sexual transmission of the virus, and facilitated by prior infections with other sexually transmitted disease (STD) pathogens. Although treatment of these STDs has been proposed as a means to decrease the rate of HIV-1 sexual transmission, preventive measures effective against both HIV-1 and other STD pathogens are expected to have a larger impact. These measures include topically applied mechanical and chemical (i.e. microbicidal) barriers. Microbicides of preference should have a broad specificity against diverse STD pathogens and a well established safety record, considering their repeated use over decades. Here, we report that cellulose acetate phthalate (CAP), an "inactive" pharmaceutical excipient, commonly used in the production of enteric tablets and capsules: (1) has antiviral activity against HIV-1 and several herpesviruses (HSV); and (2) when appropriately formulated, in micronized form, inactivates HIV-1, HSV-1, HSV-2, cytomegalovirus, Neisseria gonorrhoeae, Trichomonas vaginalis, Haemophilus ducreyi and Chlamydia trachomatis but does not affect Lactobacilli, components of the natural vaginal flora contributing to resistance against STDs. Thus, the CAP formulations meet the criteria for preferred microbicides and warrant further evaluation in vivo in humans.

Animals↗

PubMed2001

Subgingival strains of Candida albicans in relation to geographical origin and occurrence of periodontal pathogenic bacteria.

Clonal diversity of subgingival yeast strains was determined in relation to geographical location and coexistence of selected periodontal pathogenic bacteria. A total of 60 dental patients from Finland, the United States and Turkey each contributed five Candida albicans isolates. C. albicans isolates were serotyped using slide agglutination and genotyped using polymerase chain reaction (PCR) amplification and a random sequence primer. In general, each study subject yielded C. albicans isolates belonging to the same serotype and genotype. C. albicans serotype A occurred more frequently in subjects from Finland and Turkey than in subjects from the United States. A total of 27 PCR-based C. albicans genotypes were identified. One C. albicans genotype occurred with particularly high frequency in subjects from Turkey and another genotype in subjects from the United States. Relationships were identified between C. albicans serotypes and genotypes. Further studies are needed to determine environmental factors of importance for subgingival colonization and persistence of C. albicans.

Adult↗

PubMed2003

In the belly of the beast: subversion of macrophage proinflammatory signalling cascades during Toxoplasma gondii infection.

Macrophages (MØ) are used as the intracellular niche by several bacterial and protozoan microorganisms. Such microbial pathogens adopt diverse strategies to avoid MØ microbicidal effects. Recent insights into the Toxoplasma gondii-MØ interaction reveal novel ways that intracellular parasites subvert MØ function. In contrast to some microbial pathogens, Toxoplasma infection is not silent but induces rapid activation of transcription factors such as STAT-1 and NFkappaB. However, the parasite blocks nuclear translocation of both factors, and MØ cannot produce IL-12 or TNF-alpha when subsequently triggered with lipopolysaccharide. The nuclear import blockade is lifted 24 h after infection, but cells remain actively suppressed in TNF-alpha production. Nevertheless, IL-12 synthesis is initiated at this later time point. Toxoplasma gondii-induced production of this cytokine occurs through both MyD88- and CCR5-dependent pathways. The balance of cytokine subversion and stimulation during infection probably results from the parasite's need to simultaneously avoid immune elimination and trigger immunity to prevent host death.

Adaptor Proteins, Signal Transducing↗

PubMed1998

One phytopathologist's growth through ipm to holistic plant health: the key to approaching genetic yield potential.

I relate my becoming a phytopathologist and my very satisfying growth into and beyond IPM to holistic plant health, and puzzle over paradigms that have prevented our accepting the overwhelming logic of (a) seeking defensible disease-loss data to justify funding and guide research and management priorities, (b) managing genetic diversity to retard pathogen development, (c) conserving genetic diversity in situ, and (d) educating and training general practitioner plant doctors. These multidisciplinary health care professionals are key to overcoming sources of stress that cause major world crops to yield only 15-20% of their genetic potential, on average. Thus, plant doctors give hope for approaching attainable yield and feeding a hungry world-if, simultaneously, human population growth is reduced. The plant health movement has the potential to effect the greatest change in world agriculture since the Green Revolution, and the DPH/M to become plant agriculture's most important single degree program.

Journal Article↗

PubMedDate not supplied

Are biological antagonists an alternative to synthetic fungicides for preventing postharvest diseases of fruits and vegetables?

In recent years, both the public and health authorities have become increasingly concerned about the presence of pesticides in our food supply and the environment. As a direct result of this mounting concern, research efforts for the development of alternative methods for the control of postharvest diseases of fruits and vegetables have been intensified. Considerable attention has been placed on assessing the potential of the use of biological antagonists as a viable alternative to the use of synthetic fungicides. Naturally occurring microbial antagonists have been shown to control several rot pathogens on diverse commodities. Such antagonists have various modes of action: antibiosis or competition for nutrients and space or both, induction of resistance in the host tissue, and direct interaction with the pathogen. The commercialization of certain antagonists to control postharvest decay of fruits and vegetables appears to be feasible and may present an alternative to synthetic pesticides.

Agriculture↗

PubMed2000

Emerging resistance problems among respiratory tract pathogens.

The number-1 indication for antibiotic prescriptions in the United States is a respiratory tract infection. The changing spectrum of pathogens and emerging bacterial resistance are changing the way these infections are managed. The epidemiology of community-acquired pneumonia has changed significantly in the past 20 years, with increased diversity of pathogens and mortality. Emerging resistance in respiratory tract pathogens, particularly to beta-lactams, is an increasing concern. Of the important gram-negative pathogens, more than a third of Haemophilus influenzae isolates are now resistant to beta-lactam antibiotics, as well as virtually all isolates of Moraxella catarrhalis. Of the gram-positive organisms, more than 40% of Streptococcus pneumoniae isolates are no longer susceptible to penicillin, and methicillin resistance has been reported in up to half of Staphylococcus aureus isolates in some institutions. Among staphylococci, resistance to the beta-lactam methicillin is often accompanied by resistance to multiple classes of antibiotics, particularly the macrolides. Little resistance to fluoroquinolones has been reported among gram-negative respiratory tract pathogens and S pneumoniae, although increasing resistance may be seen as these drugs are used with increasing frequency. In contrast, fluoroquinolone resistance can develop rapidly in S aureus and appears to be associated with methicillin resistance. Fortunately, many of the newer fluoroquinolones appear to offer significant activity against methicillin-resistant S aureus isolates and are active against ciprofloxacin-resistant strains of S pneumoniae. Today, to combat respiratory tract infections, a broad-based empiric therapy needs to be used and bacterial resistance must be taken into account. New antimicrobial options must be considered, with an emphasis on effective drug use and optimal dosing. Even if a direct relationship between antibiotic resistance and clinical outcomes in the treatment of pneumonia in adults has not been extensively demonstrated, the increasing problem of resistance has changed treatment approaches for respiratory tract infections as a whole.

Anti-Infective Agents↗

PubMed2003

Analysis of genome plasticity in pathogenic and commensal Escherichia coli isolates by use of DNA arrays.

Genomes of prokaryotes differ significantly in size and DNA composition. Escherichia coli is considered a model organism to analyze the processes involved in bacterial genome evolution, as the species comprises numerous pathogenic and commensal variants. Pathogenic and nonpathogenic E. coli strains differ in the presence and absence of additional DNA elements contributing to specific virulence traits and also in the presence and absence of additional genetic information. To analyze the genetic diversity of pathogenic and commensal E. coli isolates, a whole-genome approach was applied. Using DNA arrays, the presence of all translatable open reading frames (ORFs) of nonpathogenic E. coli K-12 strain MG1655 was investigated in 26 E. coli isolates, including various extraintestinal and intestinal pathogenic E. coli isolates, 3 pathogenicity island deletion mutants, and commensal and laboratory strains. Additionally, the presence of virulence-associated genes of E. coli was determined using a DNA "pathoarray" developed in our laboratory. The frequency and distributional pattern of genomic variations vary widely in different E. coli strains. Up to 10% of the E. coli K-12-specific ORFs were not detectable in the genomes of the different strains. DNA sequences described for extraintestinal or intestinal pathogenic E. coli are more frequently detectable in isolates of the same origin than in other pathotypes. Several genes coding for virulence or fitness factors are also present in commensal E. coli isolates. Based on these results, the conserved E. coli core genome is estimated to consist of at least 3,100 translatable ORFs. The absence of K-12-specific ORFs was detectable in all chromosomal regions. These data demonstrate the great genome heterogeneity and genetic diversity among E. coli strains and underline the fact that both the acquisition and deletion of DNA elements are important processes involved in the evolution of prokaryotes.

Electrophoresis, Gel, Pulsed-Field↗

PubMed2004

The Role of the Intestinal Tract As a Source for Transmission of Nosocomial Pathogens.

The intestinal tract provides an important source for transmission of many nosocomial pathogens, including Enterococcus species, Clostridium difficile, Candida species, Enterobacteriaceae, and other gram-negative bacilli. Recent data suggest that the intestinal tracts of hospitalized patients may also be an important reservoir of Staphylococcus aureus. Although the clinical manifestations of these pathogens are diverse, a common pathogenesis is involved in their colonization of and dissemination from the intestinal tract. Of particular importance is the role that antibiotic selective pressure plays in promotion of colonization by antibiotic-resistant pathogens. Strategies to limit the spread of these pathogens must include efforts to improve adherence to standard infection control practices and promotion of good antimicrobial stewardship. New strategies that include application of novel technologies to the problem of pathogen transmission are needed, and additional research is needed to clarify the potential utility of selective decontamination of the digestive tract.

Journal Article↗

PubMed1998

Helicobacter pylori--molecular genetics and diagnostic typing.

The genome of H. pylori is 1.68-1.73 Mb in size and contains a relatively low GC content (an average of 32.5 mol%). Physical and genetic maps of five H. pylori strains (NCTC 11637, NCTC 11638, NCTC 11639, UA 802 and UA 861) have been constructed and the complete genome sequence of strain 26695 has been determined. At least 50 genes, some of which play important roles in the physiology and pathogenicity of the bacterium, have been cloned. Marked genomic sequence variability has evolved from stain to strain demonstrated by random arrangement of 17 known genes on the chromosome and frequent mutations within individual genes. Based on such variability, sensitive and efficient molecular tying techniques such ribotyping, AR-PCR, PCR-RFLP, PCR-DNA sequencing and PFGE-RFLP have been developed and widely applied in both epidemiological and clinical studies of this pathogen. Subtypes of vacA (encoding a vacuolating cytotoxin) and the intermediate forms of a pathogenicity island (the cag region) have been identified in different H. pylori strains and these individual vacA subtypes are associated with specific clinical manifestations of H. pylori infection. Further studies on relationships between the genetic diversity and pathogenicity of H. pylori strains would lead to the development of novel and efficient therapeutic strategies for eradication of this microorganism.

Bacterial Typing Techniques↗

PubMed2003

Microbial diversity and prevalence of virulent pathogens in biofilms developed in a water reclamation system.

Bacterial biofilm is a common phenomenon in both natural and engineered systems which often becomes a source of contamination and microbially influenced corrosion. It is thought that formation of biofilm in the monoculture of several bacterial species is regulated by acylhomoserine lactone (AHL) quorum-sensing signals. In this study, we investigated the microbial diversity and existence of AHL-producing and AHL-degrading bacterial species in the biofilm samples from a water reclamation system located in a tropical environment. 16S ribosomal DNA sequencing analysis indicated the presence of at least 11 bacterial species, including the frequently encountered bacterial pathogens Pseudomonas aeruginosa and Klebsiella pneumoniae, and several rare pathogens. We showed that only two groups of isolates, belonging to P. aeruginosa and Enterobacter agglomerans, produced AHL signals. We also found that three bacterial isolates, i.e., Agrobacterium tumefaciens XJ01, Bacillus cereus XJ08, and Ralstonia sp. XJ12, expressed AHL degradation enzymes. Furthermore, we showed that P. aeruginosa isolate HL43 was virulent against animal model Caenorhabditis elegans and released 2-6-fold more pyocyanin cytotoxin than P. aeruginosa strains PA01 and PA14, the two commonly used laboratory strains. These data indicate the complexity and importance of biofilm research in water reclamation.

Animals↗

PubMed2022

Pneumococcal within-host diversity during colonization, transmission and treatment.

Characterizing the genetic diversity of pathogens within the host promises to greatly improve surveillance and reconstruction of transmission chains. For bacteria, it also informs our understanding of inter-strain competition and how this shapes the distribution of resistant and sensitive bacteria. Here we study the genetic diversity of Streptococcus pneumoniae within 468 infants and 145 of their mothers by deep sequencing whole pneumococcal populations from 3,761 longitudinal nasopharyngeal samples. We demonstrate that deep sequencing has unsurpassed sensitivity for detecting multiple colonization, doubling the rate at which highly invasive serotype 1 bacteria were detected in carriage compared with gold-standard methods. The greater resolution identified an elevated rate of transmission from mothers to their children in the first year of the child's life. Comprehensive treatment data demonstrated that infants were at an elevated risk of both the acquisition and persistent colonization of a multidrug-resistant bacterium following antimicrobial treatment. Some alleles were enriched after antimicrobial treatment, suggesting that they aided persistence, but generally purifying selection dominated within-host evolution. Rates of co-colonization imply that in the absence of treatment, susceptible lineages outcompeted resistant lineages within the host. These results demonstrate the many benefits of deep sequencing for the genomic surveillance of bacterial pathogens.

Child↗

PubMed2006

AGS3, an alpha(1-3)glucan synthase gene family member of Aspergillus fumigatus, modulates mycelium growth in the lung of experimentally infected mice.

The cell wall of human fungal pathogen Aspergillus fumigatus protects the fungus against threats from environment and interacts with the host immune system. Alpha(1-3)glucan is the major polysaccharide of Aspergillus fumigatus cell wall, and it has been shown to contribute to the virulence of diverse fungal pathogens. In A. fumigatus, three putative alpha(1-3)glucan synthase genes AGS1, AGS2 and AGS3 have been identified. AGS1 is responsible for cell wall alpha(1-3)glucan biosynthesis, but strains with deletions of either AGS1 or AGS2 are not defective in virulence [Beauvais, A., Maubon, D., Park, S., Morelle, W., Tanguy, M., Huerre, M., Perlin, D.S., Latgé, J. P., 2005. Two alpha(1-3) glucan synthases with different functions in Aspergillus fumigatus. Appl. Environ. Microbiol. 71, 1531-1538]. In contrast, we present evidence that AGS3 is also responsible for cell wall alpha(1-3)glucan biosynthesis and can modulate the virulence of A. fumigatus. An AGS3 deletion strain was found to produce faster and more robust disease than the parental strain in an experimental mouse model of aspergillosis. The apparent hyper-virulence in the AGS3-deleted mutant was correlated with an increased melanin content of the conidial cell wall, a better resistance to reactive oxygen species and a quicker germination rate. These results suggest an indirect role for AGS3 in virulence through an adaptive mechanism.

Animals↗

PubMed2003

Combinatorial immunoglobulin light chain variability creates sufficient B cell diversity to mount protective antibody responses against pathogen infections.

To analyze how combinatorial light (L) chain diversity influences the B cell repertoire, we studied mice with a homozygous immunoglobulin-heavy-chain null mutation (mu MT), in which the B cell developmental block was overridden by the expression of a transgenic immunoglobulin mu heavy (H) chain derived from a vesicular stomatitis virus Indiana serotype (VSV-IND)-neutralizing Ab (T11 mu MT mice). The randomly integrated transgene could not undergo secondary rearrangements and was expressed in combination with endogenous kappa or lambda chains. T11 mu MT mice had a skewed B cell repertoire as evidenced by 30-60% VSV-IND-specific peripheral B cells and spontaneous VSV-IND-neutralizing serum titers. Upon immunization, T11 mu MT mice mounted specific IgM antibody responses against VSV-IND but, interestingly, they also responded against VSV New Jersey serotype (VSV-NJ), lymphocytic choriomeningitis virus, poliovirus and Salmonella typhi porins. Variable-region sequence analysis revealed that VSV-NJ-specific antibodies expressed numerous L chains in combination with the transgenic H chain, which was devoid of hypermutations. Thus, in T11 mu MT mice combinatorial L chain variability alone is able to build up a sufficiently complex B cell repertoire to mount protective immunoglobulin responses against a variety of pathogens.

Animals↗

PubMed1998

The Yersinia Yops inhibit invasion of Listeria, Shigella and Edwardsiella but not Salmonella into epithelial cells.

Yersinia virulence is dependent on the expression of plasmid-encoded secreted proteins called Yops. After bacterial adherence to receptors on the mammalian cell membrane, several Yops are transported by a type III secretion pathway into the host cell cytoplasm. Two Yops, YopH and YopE, prevent macrophages from phagocytosing Yersinia by disrupting the host cell cytoskeleton and signal transduction pathways. In contrast to this active inhibition of phagocytosis by Yersinia, other pathogens such as Salmonella, Shigella, Listeria and Edwardsiella actively promote their entry into mammalian cells by binding to specific host surface receptors and exploiting existing cell cytoskeletal and signalling pathways. We have tested whether Yersinia Yops can prevent the uptake of these diverse invasive pathogens. We first infected epithelial cells with Yersinia to permit delivery of Yops and subsequently with an invasive pathogen. We then measured the level of bacterial invasion. Preinfection with Yersinia inhibited invasion of Edwardsiella, Shigella and Listeria, but not Salmonella. Furthermore, we found that either YopE or YopH prevented Listeria invasion, whereas only YopE prevented Edwardsiella and Shigella invasion. We correlated the inhibitory effect of the Yops with the inhibitory action of the cell-signalling inhibitors Wortmannin, LY294002 and NDGA, and concluded that the four invasive pathogenic species enter epithelial cells using at least three distinct host cell pathways. We also speculate that YopE affects the rho pathway.

Androstadienes↗

PubMed2002

Toll-like receptors: a family of pattern-recognition receptors in mammals.

The innate immune system uses a variety of germline-encoded pattern-recognition receptors that recognize conserved microbial structures or pathogen-associated molecular patterns, such as those that occur in the bacterial cell-wall components peptidoglycan and lipopolysaccharide. Recent studies have highlighted the importance of Toll-like receptors (TLRs) as a family of pattern-recognition receptors in mammals that can discriminate between chemically diverse classes of microbial products. First identified on the basis of sequence similarity with the Drosophila protein Toll, TLRs are members of an ancient superfamily of proteins, which includes related proteins in invertebrates and plants. TLRs activate innate immune defense reactions, such as the release of inflammatory cytokines, but increasing evidence supports an additional critical role for TLRs in orchestrating the development of adaptive immune responses. The sequence similarity between the intracellular domains of the TLRs and the mammalian interleukin-1 and interleukin-18 cytokine receptors reflects the use of a common intracellular signal-transduction cascade triggered by these receptor classes. But more recent findings have demonstrated that there are in fact TLR-specific signaling pathways and cellular responses. Thus, TLRs function as sentinels of the mammalian immune system that can discriminate between diverse pathogen-associated molecular patterns and then elicit pathogen-specific cellular immune responses.

Animals↗

PubMed2003

Susceptibility of hematopoietic stem cells to pathogens: role in virus/bacteria tropism and pathogenesis.

Human hematopoietic stem cells (HSCs) are generated in the bone marrow and differentiate into erythrocytes, granulocytes, monocytes, megacaryocytes, and lymphocytes. HSCs may be manipulated under different conditions. Advances in cell biology result in a better understanding of the relationship between viruses/bacteria and hematopoietic cells. Microbial infections can lead to profound disturbance of hematopoiesis. Infection may augment the production of cytokines, with proliferation and differentiation of the stem cells. Alternatively, infection may lead to destruction of progenitor cells. This results in defective hematopoiesis in certain infections. Since circulating CD34+ cells represent a distinct progenitor pool responsible for seeding extramedullary sites of hematopoiesis, infected peripheral blood-derived CD34+ progenitor cells may serve to disseminate pathogens into diverse anatomic sites. Therefore, progenitor cell infection may additionally effect long-term functional consequences within extramedullary sites of lymphopoiesis. A variety of viruses have been reported to target HSCs, whereas quiescent human HSCs are fully resistant to infection by different bacteria. For susceptibility of HSCs to infectious agents pathogen-receptor interaction plays an important role in virus/bacteria tropism and pathogenesis.

Bacteria↗