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Results for “Host Microbial Interactions”

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PubMed1999

Necrotizing ulcerative periodontitis.

In patients with no known systemic disease or immune dysfunction, necrotizing periodontitis (NUP) appears to share many of the clinical and etiologic characteristics of necrotizing ulcerative gingivitis (NUG) except that patients with NUP demonstrate loss of clinical attachment and alveolar bone at affected sites. In these patients, NUP may be a sequela of a single or multiple episodes of NUG or may be the result of the occurrence of necrotizing disease at a previously periodontitis-affected site. The existence of immune dysfunction may predispose patients to NUG and NUP, especially when associated with an infection of microorganisms frequently associated with periodontal disease such as Treponema and Selenomonas species, Fuscobacterium nucleatum, Prevotella intermedia, and Porphyromonas gingivalis. The role of immune dysfunction is exemplified by the occasionally aggressive nature of necrotic forms of periodontal disease seen in patients with HIV infection or malnutrition, both of which may impact host defenses. Clinical studies of HIV-infected patients have shown that patients with NUP are 20.8 times more likely to have CD4+ cell counts below 200 cells/mm3. However, these same studies have demonstrated that most patients with CD4+ cell counts below 200 cells/mm do not have NUP, suggesting that other factors, in addition to immunocompromisation, are involved. Further studies are needed to define the complex interactions between the microbial, or viral, etiology of necrotic lesions and the immunocompromised host. It is, therefore, recommended that NUG and NUP be classified together under the grouping of necrotizing periodontal diseases based on their clinical characteristics.

Disease Progression↗

PubMed1993

Biocompatibility: its future in prosthodontic research.

The future of prosthodontic research will involve replacing lost tissues by using scientific methods that evaluate biomaterials and treatment designs based on desired biologic outcomes. The present concept of a biocompatible material is one that elicits an appropriate host response in a specific application. To design optimal biomaterials, three interactive components should be considered: the chemical nature of the surface, the mediating pellicle layer, and microbial and host response. Surface chemistry determines which molecules are selectively absorbed onto a surface from oral fluids. The pellicle-coated surface should be designed to elicit a more desirable host response. Pellicle composition can be altered by chemically changing the surface, precoating surfaces with biological molecules, or using synthetic materials designed to mimic natural tissues. Several surface-sensitive techniques are available to assess these modifications, including vibrational spectroscopy, electron microscopy for chemical analysis, and bioanalytical methods. To develop more biocompatible materials, a further understanding of pellicle formation as a function of surface composition, microbial adhesion to biomaterials, and cellular reaction to implant biomaterials is necessary. This knowledge will facilitate development of new biologically based rationales for treatment modalities in restorative dentistry.

Biocompatible Materials↗

PubMed2001

Pathogenic trickery: deception of host cell processes.

Microbial pathogens cause a spectrum of diseases in humans. Although the disease mechanisms vary considerably, most pathogens have developed virulence factors that interact with host molecules, often usurping normal cellular processes, including cytoskeletal dynamics and vesicle targeting. These virulence factors often mimic host molecules, and mediate events as diverse as bacterial invasion, antiphagocytosis, and intracellular parastism.

Animals↗

PubMed1991

Molecular cross talk between epithelial cells and pathogenic microorganisms.

The conference brought together epithelial cell biologists and molecular microbiologists and emphasized that these seemingly diverse disciplines are intricately intertwined. The model systems discussed throughout the meeting emphasized the novel approaches available to address key issues and begin to understand the molecular details of responses triggered at the microbial-epithelial interface. For example, co-crystallization of native ligand-receptor complexes as well as biologically or chemically altered forms of these complexes will allow fine details of receptor-ligand interactions to be determined. This approach is critical in development of new generation antimicrobial agents. Furthermore, transfection techniques that allow receptor expression in model epithelia, development of representative animal model systems, and development of transgenic mouse strains will aid in dissecting microbial-epithelial interactions and will provide further advances in studies on pathogenesis and tissue and host tropism. We are only beginning to uncover the nature of the bidirectional regulatory signals that occur between microbes and hosts. We know little about how these signals relate to the disease state, to microbial virulence, or to immune function. Clearly the cross talk between cell biologists and microbiologists is an important step in unraveling the events occurring between microbes and eukaryotic cells.

Animals↗

PubMed2000

Oral microbial communities: biofilms, interactions, and genetic systems.

Oral microbial-plaque communities are biofilms composed of numerous genetically distinct types of bacteria that live in close juxtaposition on host surfaces. These bacteria communicate through physical interactions called coaggregation and coadhesion, as well as other physiological and metabolic interactions. Streptococci and actinomyces are the major initial colonizers of the tooth surface, and the interactions between them and their substrata help establish the early biofilm community. Fusobacteria play a central role as physical bridges that mediate coaggregation of cells and as physiological bridges that promote anaerobic microenvironments which protect coaggregating strict anaerobes in an aerobic atmosphere. New technologies for investigating bacterial populations with 16S rDNA probes have uncovered previously uncultured bacteria and have offered an approach to in situ examination of the spatial arrangement of the participant cells in oral-plaque biofilms. Flow cells with saliva-coated surfaces are particularly useful for studies of biofilm formation and observation. The predicted sequential nature of colonization of the tooth surface by members of different genera can be investigated by using these new technologies and imaging the cells in situ with confocal scanning laser microscopy. Members of at least seven genera now can be subjected to genetic studies owing to the discovery of gene-transfer systems in these genera. Identification of contact-inducible genes in streptococci offers an avenue to explore bacterial responses to their environment and leads the way toward understanding communication among inhabitants of a multispecies biofilm.

Bacteria↗

PubMed1983

Cell biology of host-parasite membrane interactions in leishmaniasis.

Molecular interactions at the host-parasite interface are crucial for the outcome of microbial infection, particularly in infection by intracellular parasites, such as Leishmania donovani and Leishmania mexicana, whose natural transmission begins with the delivery of the promastigote stage by the sandfly vector into the susceptible host. The ensuing event is intracellular parasitism of macrophages in the host by the amastigote stage. The establishment of this event in leishmaniasis must follow the sequence: (1) Leishmania-macrophage attachment; (2) entry of Leishmania species into macrophages; (3) intra-macrophage survival and differentiation of Leishmania species; and (4) intracellular multiplication of Leishmania species. This sequence precedes all clinical symptoms and pathological consequences in different forms of the disease. Study of these cellular events in Leishmania-macrophage systems in vitro indicates that host-parasite membrane interactions dictate many of the cellular events. Some morphological and functional changes of macrophages in response to leishmanial infection are related to their membrane activities, i.e. endocytosis and exocytosis. Leishmania parasites undergo profound plasma membrane-related changes, on entry into macrophages, at the morphological, antigenic and molecular levels. Most of these changes probably reflect necessary steps for the transition of Leishmania species from an extracellular to an intracellular life. The remarkable ability of Leishmania species subsequently to live in the secondary lysosome of the macrophage may also be due to certain intrinsic structures and dynamic properties of the parasite plasma membrane. Further analysis of leishmanial surface molecules and their interactions with macrophages is essential in any attempt to understand the pathogenic mechanism in leishmaniasis.

Animals↗

PubMed2005

Animal models of intestinal inflammation: ineffective communication between coalition members.

The microbiota, epithelial cells, and mucosal immune cells in the intestine comprise an important gastrointestinal coalition. The intestinal microbiota can exert both beneficial as well as deleterious effects on their animal hosts. They interact with the innate defenses provided by epithelial cells through microbial recognition receptors. This communication, under normal conditions, results in a state of controlled inflammation. This article will focus on several animal models of intestinal inflammation, in which spontaneous or induced mutations or other genetic manipulations result in severe alterations in one of the members of the gastrointestinal coalition. These animal models of colitis have shown that alterations in communication between members of this coalition ultimately lead to gastrointestinal disease.

Animals↗

PubMed1980

The symbiotic microbial community of the Sonoran Desert termite: Pterotermes occidentis.

Pterotermes occidentis is a large, obscure, very primitive dry wood termite limited to the Sonoran desert of North America. Its development, caste system and behavior are discussed in relation to aspects of its ecology. What appear to be single wood-digesting individual termites are in fact insect hosts which harbor extensive microbial communities estimated to contain more than 40 interacting species. All healthy, wood-eating Pterotermes contain these densely populated communities of highly motile symbionts suggesting that species diversity is necessary for termite survival. A morphological catalogue of the major hindgut microbes is presented here. From 10(7) to 10(11) bacteria and from 10(3) to 10(6) protists/ml of hindgut fluid are found in an average nymph or larva. The species of four wood-ingesting mastigotes (genera Trichonympha, Metadevescovina, Tricercomitus and Microrhopalodina) and nearly 30 morphologically distinct types of bacteria are described. The description of this morphological diversity observed with light, scanning and transmission electron microscopy is a prerequisite to functional analyses of the symbioses. Since Pterotermes is easily maintained in the laboratory and is so large it is hoped that it will provide a useful model for symbiosis research.

Animals↗

PubMed2000

Novel approaches to monitor bacterial gene expression in infected tissue and host.

Elucidating the complex and dynamic host-microbe interactions during infection requires, among other things, detailed knowledge of microbial gene expression in vivo. Recently, advances in fluorescence and bioluminescence detection techniques, as well as recombinase-based in vivo expression technology, have rendered monitoring virulence gene expression in vivo a feasible task. These techniques have been adapted by several laboratories to study the spatial and temporal patterns of virulence gene expression by organisms such as Salmonella typhimurium, Listeria monocytogenes, Yersinia entercolitica and Vibrio cholerae during infection of tissue culture or animal models of infection.

Animals↗

PubMed2000

Intravascular catheter-related infections: a preventable challenge in the critically ill.

In modem medicine, central venous catheters (CVCs) have a pivotal role in the management of critically ill patients. The most serious complication of effective CVC placement is catheter-related bloodstream infection (CRBSI). Microbial colonization and CRBSI are the byproducts of the interaction of 4 factors: (1) microbial factors (hydrophobicity and exopolysaccharide production), (2) host factors (such protein adhesins as fibrin and fibronectin that attach to the catheter surface), (3) catheter material (hydrophobicity, surface charges, thrombogenicity), and (4) iatrogenic factors (total parenteral nutrition, interleukin-2). The organisms most frequently associated with CRBSI are Staphylococcus epidermidis, Staphylococcus aureus, and Candida spp. CRBSIs were traditionally diagnosed through semiquantitative or quantitative cultures of the catheter tip. However, the diagnosis can be achieved without catheter removal through cultures of blood specimens collected simultaneously though the CVC and a peripheral vein. Currently, the most effective method of preventing a CRBSI is the use of a CVC coated with antimicrobial agents. Intravenous administration of vancomycin for 7 days is adequate for an uncomplicated CRBSI caused by coagulase-negative staphylococci, and at least 10 days of therapy with beta-lactams is required for an uncomplicated infection caused by methicillin-sensitive S. aureus. CRBSI caused by Candida albicans or Candida parapsilosis can be treated with at least 14 days of therapy with fluconazole or amphotericin B. In the case of Candida krusei, only amphotericin B is effective.

Bacteremia↗

PubMed2006

Towards a vaccine for Cryptococcus neoformans: principles and caveats.

In the Damage-response framework of microbial pathogenesis, infectious diseases are one outcome of a host-microorganism interaction in a susceptible host. In cryptococcal disease, damage to the host is caused by Cryptococcus neoformans virulence determinants, the nature of the host response, or both. Further, the disease may be acute or reactivated from a latent state. Hence, a vaccine for C. neoformans would need to prevent disease resulting from either acute or reactivated infection. The evidence to support the development of a vaccine for C. neoformans that induces antibody-mediated immunity is discussed herein.

Animals↗

PubMed1986

Microbiological evaluation of the intraruminal in sacculus digestion technique.

The influence of nature of the feed sample, feeding frequency and pore size on the influx of bacteria and protozoa into synthetic fiber bags suspended in the rumens of sheep fed different diets was studied. Counts of total culturable bacteria in bags with a pore size of 10 microns were less than 30% of the ruminal counts for animals that were fed the lucerne hay and high-roughage diets. The maximum count (62 and 82% of the ruminal count) for these specific diets was obtained by using bags with a pore size of 53 microns. Protozoal counts in bags with pore sizes of 30 and 53 microns were equal to or higher than the ruminal counts for the lucerne hay and high-roughage diets but less than half of the ruminal count for the low-roughage diet. An interaction between incubation time, feeding frequency of the host animals, and the microbial populations developing inside the bags was also demonstrated. The results clearly show that the microbial population inside the bag differed from that of the surrounding ruminal ingesta and that caution must be taken in interpreting results on feed evaluation and especially on rates of degradation when using the in sacculus technique. Factors influencing the influx of bacteria and protozoa into bags with different pore sizes and containing a variety of substrates are discussed together with suggestions for the use of this technique.

Animal Feed↗

PubMedDate not supplied

[Physiopathology of alveolar bone].

Bone tissue is a dynamic system in which the net balance between resorption and apposition defines the final osseous form. This process occurs in minute asynchronous foci and results from a cascade of activations, cooperations and inhibitions of specialized cells (osteoblasts and osteoclasts). The alveolar bone resorption due to periodontal disease is a complex and dynamic chain reaction in which both osteoclasts and osteoblasts have a role in the hormonal interactions occurring during the course of the resorption activity. Both microbial and host factors as prostaglandins, endotoxins and lipoteic acid seems to be able in activating bone resorption. However bone resorption can be interchanged with repair formative episodes, more or less intense, which can delay the destructive process.

Alveolar Process↗

PubMed2004

The involvement of an integrin-like protein and protein kinase C in amoebic adhesion to fibronectin and amoebic cytotoxicity.

Adherence of a pathogen to the host cell is one of the critical steps in microbial infections. Naegleria fowleri, a causative agent of primary amoebic meningoencephalitis in humans, is expected to interact with extracellular components of the host, such as fibronectin, in a receptor-mediated mode. In this study, we investigated the interaction between N. fowleri and fibronectin to understand its cytopathology. In binding assays using immobilized fibronectin, the number of amoebae bound to fibronectin was increased compared to the controls, and was dependent on the amount of coated fibronectin present. A fibronectin binding protein of 60 kDa was found in extracts of N. fowleri. Western blot and immunolocalization assays using integrin alpha(5)/FnR antibodies showed that a 60 kDa protein reacted with the antibodies in extracts of N. fowleri, which was localized on the surface of N. fowleri. Preincubation of N. fowleri with the integrin antibodies significantly inhibited amoebic binding to fibronectin and cytotoxicity to the CHO cells. Additionally, protein kinase C activity was detected in the extract of N. fowleri. When N. fowleri was pretreated with protein kinase C activator or inhibitor, the abilities of amoebic adhesion to fibronectin and cytotoxicity to the host cells were markedly affected compared to untreated amoebae. These results suggest that an amoebic integrin-like receptor and protein kinase C play important roles in amoebic cellular processes in response to fibronectin.

Animals↗

PubMed2026

Reframing the asthma microbiome: Multikingdom, multisite, and multiomic perspectives.

The field of asthma microbiome research has shifted rapidly in recent years. Advances in sequencing technology have led to an increased ability to characterize multikingdom microbial species and integration with host -omics profiling to enhance future translational applications. Traditional bacteria-centric, cross-sectional studies are giving way to mechanistic frameworks that incorporate fungi, viruses, and host-immune interactions. In this state-of-the-art review of emerging concepts in microbiome asthma research, we first propose a structured framework to consider microbiome studies across 5 major domains-microbial kingdom, site of sampling, integration with host -omics, clinical outcome domain, and translational relevance-in order to synthesize recent high-impact human microbiome studies in asthma. We highlight emerging evidence that fungal and viral communities contribute independently to asthma risk and that human microbial communities are linked to distinct inflammatory and immune pathways shaped by host genetic susceptibility.

Asthma↗

PubMed1976

Nutritional determinants of the ecology of the oral flora.

Consideration of nutritional factors as determinants of oral microbial ecology leads to the conclusion that endogenous factors play a dominant role. It is the interactions between specific microorganisms and nutritional and other factors provided by the host that selectively determine the kinds of microorganisms which willinitially reside in the oral cavity and the sites which they will colonize. The persistence of these original "colonists" in their respective ecologic niches will depend in part on the accessibility of endogenous nutrients variously provided by saliva, tissue exudates, crevicular fluids, or degenerating host cells. It will also depend on their response to and interaction with microorganisms which immigrate to that site subsequently. The microbial ecology of a given site is therefore rarely uncomplicated, the notable exception occurring at the most microscopic level where one may encounter microcolonies of individual species within more heterogenous populations of microorganisms. The extent of this heterogeneity quantitatively and qualitatively is a reflection of the degree to which the interactions between the resident flora and the new arrivals, plus the local environmental changes which they both generate, serve to promote or to discourage the survival and growth of the individual species. This element of heterogeneity in a dynamic system with its inherent potential for variation makes it possible for relatively minor changes in local environmental conditions to result in significant differences in the microflora between one site and another even though they may be in close proximity to each other. Once this concept is appreciated it becomes easy to understand how disease processes such as dental caries may affect specific areas of a tooth while nearby areas are unaffected. The effects of exogenous nutrients on the ecology of the oral microbiota, nevertheless cannot be ignored. The diet may modulate such endogenous factors as the salivary secretions and the local resistance of the gingival tissues to infections. Although at our present state of knowledge the direct influence of dietary proteins and fats on the oral microbiota is thought to be of relatively minor consequence, dietary carbohydrates are of major ecological significance. Dietary sugars provide readily available substrates for the oral microorganisms, most of which depend on carbohydrates for energy sources. The metabolism of dietary sucrose by S. sanguis and S. mutans with the productions of acids and intracellular and extracellular polysaccharides has specific influence on the microbial composition, metabolic activities, and mass of coronal plaque. The ready availability of dietary carbohydrates undoubtedly influences the microflora of other parts of the oral cavity as well, eic species or indirectly through the interactions of other organisms with them...

Adhesiveness↗

PubMed1999

Interaction of antimicrobial peptides with biological and model membranes: structural and charge requirements for activity.

Species right across the evolutionary scale from insects to mammals use peptides as part of their host-defense system to counter microbial infection. The primary structures of a large number of these host-defense peptides have been determined. While there is no primary structure homology, the peptides are characterized by a preponderance of cationic and hydrophobic amino acids. The secondary structures of many of the host-defense peptides have been determined by a variety of techniques. The acyclic peptides tend to adopt helical conformation, especially in media of low dielectric constant, whereas peptides with more than one disulfide bridge adopt beta-structures. Detailed investigations have indicated that a majority of these host-defense peptides exert their action by permeabilizing microbial membranes. In this review, we discuss structural and charge requirements for the interaction of endogenous antimicrobial peptides and short peptides that have been derived from them, with membranes.

Amino Acid Sequence↗

PubMed1997

Prevention of urinary tract infection.

Recurrent UTI remains an exceedingly common clinical problem among women of all ages. Among otherwise healthy premenopausal and postmenopausal women, increased susceptibility to recurrences seems to be conferred by intrinsic host factors, such as nonsecretor genotype or estrogen status, and by exogenous exposures or behaviors, such as use of a diaphragm with spermicide, antimicrobial use, and sexual behavior. The natural history of recurrent UTIs is notable for a temporal clustering phenomenon, the tendency of women to revert to a baseline infection pattern after the cessation of preventive interventions, and repeated serial reinfections of the urinary tract from the fecal reservoir, often by genetically identical organisms. Low-dose antimicrobial regimens given daily, three times weekly, or postcoitally are effective in preventing recurrences in most women with a predisposition to frequent infection. Intermittent patient-initiated self-treatment is an appropriate and effective option in some patients with lower recurrence rates. In postmenopausal women, estrogen replacement therapy, particularly vaginally applied estriol creams, may also significantly reduce the rate of recurrent UTI. Ongoing investigations in the areas of microbial ecology of the vaginal flora, the molecular basis for host-parasite interactions within the urinary tract, and vaccine development may eventually lead to improved means to prevent recurrent urinary tract infections more effectively.

Adult↗