PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Microbial interactions”

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 1,747 records · Page 97Linked to original sources
PubMed2000

Two-particle model of anaerobic solid state fermentation.

A structured mathematical model of anaerobic solid state fermentation (ASSF) has been developed. Since a stable ASSF requires addition of significant quantities of methanogenic seed sludge and mass-transfer limitation becomes important, the model postulates the existence of two different types of particles inside the fermenting solid mass--so-called "seed" particles with low biodegradability and high methanogenic activity and so-called "waste" particles with high biodegradability and low methanogenic activity. Any particle is assumed to be a completely mixed reactor and mass transfer of solutes between the particles is brought about by diffusion. The model includes multiple-reaction stoichiometry, microbial growth kinetics, material balances, liquid-gas interactions and liquid phase equilibrium chemistry. The theoretical model agrees on the qualitative level with existing experimental studies of ASSF. Hypothetical computer simulations are presented to illustrate the influence of biodegradability and mass transfer intensity on the stability of ASSF. On this basis, possible measures are proposed to prevent accumulation of volatile fatty acids inside the "seed" particles beyond their assimilative methanogenic capacity.

Bacteria, Anaerobic↗
PubMed1975

Microbe ingestion and killing by neutrophils: normal mechanisms and abnormalities.

Microbial ingestion and killing by neutrophils involves the interaction between the phagocytic cells of the body and certain serum factors. The primary phagocytes of the blood are the polymorphonuclear neutrophil, eosinophil and monocyte. The fixed tissue macrophage of the reticuloendothelial system is responsible for phagocytosis and killing of encapsulated bacteria, viruses, and protozoans, whereas the blood phagocyte system is involved in killing of pyogenic bacteria and certain fungi. Proper ingestion of bacteria requires opsonisation of these bacteria by either complement of specific antibody, or an interaction of these two proteins. Opsonised bacteria are fixed to the surface of the phagocytic cells which contain receptors for IgG and C3. Following immune adherence ingestion of bacteria involves invagination of the plasmalemmal membrane. This process utilises ATP and a re-arrangement of lipids occurs during formation of the phagocytic vacuole. Granular enzymes containing peroxidase, hydrolases, and cationic proteins are transferred from the granule into the phagocytic vacuole. There is activation of oxidative metabolism with an increased consumption of oxygen leading to hydrogen peroxide production.

Anemia, Sickle Cell↗
PubMedDate not supplied

[Homologous protein domains in superkingdoms Archaea, Bacteria, and Eukaryota and the problem of the origin of eukaryotes].

The distribution of protein domains was analyzed in superkingdoms Archaea, Bacteria, and Eukaryota. About a half of eukaryotic domains have prokaryotic origin. Many domains related to information processing in the nucleocytoplasm were inherited from archaea. Sets of domains associated with metabolism and regulatory and signaling systems were inherited from bacteria. Many signaling and regulatory domains common for bacteria and eukaryotes were responsible for the cellular interaction of bacteria with other components of the microbial community but were involved in coordination of the activity of eukaryotic organelles and cells in multicellular organisms. Many eukaryotic domains of bacterial origin could not originate from ancestral mitochondria and plastids but rather were adopted from other bacteria. An archaeon with the induced incorporation of alien genetic material could be the ancestor of the eukaryotic nucleocytoplasm.

Animals↗
PubMed2006

Emerging infectious diseases at the beginning of the 21st century.

The emergence and re-emergence of infectious diseases involves many interrelated factors. Global interconnectedness continues to increase with international travel and trade; economic, political, and cultural interactions; and human-to-human and animal-to-human interactions. These interactions include the accidental and deliberate sharing of microbial agents and antimicrobial resistance and allow the emergence of new and unrecognized microbial disease agents. As the 21st century begins, already new agents have been identified, and new outbreaks have occurred. Solutions to limiting the spread of emerging infectious diseases will require cooperative efforts among many disciplines and entities worldwide. This article defines emerging infectious diseases, summarizes historical background, and discusses factors that contribute to emergence. Seven agents that have made a significant appearance, particularly in the 21st century, are reviewed, including: Ebola and Marburg hemorrhagic fevers, human monkeypox, bovine spongiform encephalopathy, severe acute respiratory syndrome (SARS), West Nile virus, and avian influenza. The article provides for each agent a brief historical background, case descriptions, and health care implications.

Animals↗
PubMed1990

In vitro antimicrobial activity of a novel aminothiazolylglycylcephalosporin, MT0703S, compared with that of ceftazidime, cefoperazone and aztreonam.

The antibacterial activity of a novel aminothiazolylglycylcephalosporin, MT0703S, possessing a dihydroxypyridone moiety was compared in vitro with the activity of ceftazidime, cefoperazone, aztreonam and other beta-lactam antibiotics using seven bacterial species of a clinical origin. MT0703S showed the most potent activity against P. aeruginosa, including the ceftazidime-resistant strains, E. coli, K. pneumoniae and C. freundii. MT0703S was comparable to aztreonam but more active than ceftazidime and cefoperazone in its activity against K. oxytoca and E. cloacae, and comparable to ceftazidime against S. aureus and S. marcescens. MT0703S was more active than cefoperazone against S. marcescens but less active against S. aureus. The stability of MT0703S against various beta-lactamases appeared to be intermediate between the stability of ceftazidime and that of cefoperazone. The antimicrobial activity of MT0703S increased in a low-iron environment and decreased in a high ferric ion concentration.

Aztreonam↗
PubMed1989

In vitro bactericidal activity and post-antibiotic effect of dactimicin, a new aminoglycoside, alone and in combination with other antibiotics.

The bactericidal activity of dactimicin, a novel aminoglycoside, has been tested in vitro in combination with piperacillin, mezlocillin and ceftazidime against freshly isolated Gram-negative and Gram-positive aerobes and compared with that of amikacin. Using the checkerboard test, the combination of dactimicin and amikacin with the other drugs resulted in a synergistic interaction with the Enterobacteriaceae strains analysed in 36 out of 39 and 37 out of 39 cases, respectively. Antagonism was never encountered. With the Pseudomonas isolates, indifference prevailed with dactimicin, whereas synergism was observed with amikacin in combination with the other drugs. No case of antagonism was encountered. When the time-kill system was employed, synergism prevailed, indifference was a rare case, and antagonism was not observed. In experiments carried out with dactimicin-susceptible staphylococcal and enterococcal isolates, a synergistic outcome was obtained employing both methods. Dactimicin induced a post-antibiotic effect (PAE) which ranged from about 1 h with Enterobacter cloacae to 3 h with Escherichia coli after exposure of the bacteria for 1 h to 4 x MIC. The PAE was also evaluated employing several drug associations. An average of 0.6 h PAE was apparent when dactimicin was combined with piperacillin, mezlocillin and ceftazidime, and the bacteria were exposed for 1 h to drug concentrations corresponding to one-half their MICs.

Aminoglycosides↗
PubMed1987

Antistaphylococcal activity of teicoplanin in association with other antibiotics.

The in vitro activity of antibiotic combination of teicoplanin and gentamicin (or netilmicin) and teicoplanin and cephalotin on Staphylococcus aureus was evaluated using the checkerboard method and time-kill curves. With few exceptions neither antagonism nor synergism was seen for the combination of teicoplanin and aminoglycosides using the checkerboard method. Using time-kill curves synergism was often found for the combination of teicoplanin and netilmicin (even at sub-minimal inhibitory concentrations of netilmicin) and for the combination of teicoplanin and cephalotin. No antagonistic interactions occurred.

Anti-Bacterial Agents↗
PubMed1977

Antimicrobial agents--Part II. The aminoglycosides: streptomycin, kanamycin, gentamicin, tobramycin, amikacin, neomycin.

Aminoglycoside antibiotics are poorly absorbed from the gastrointestinal tract, do not penetrate well into the cerebrospinal fluid, are minimally bound to plasma proteins, and are rapidly excreted by the normal kidney. Neomycin is limited by its toxicity to irrigating and topical preparations or to oral medication for surgical bowel preparations or hepatic coma. Streptomycin has only a few specific indications, because newer agents are available that have broader spectrums of activity. Kanamycin is indicated in serious gram-negative infections in which Pseudomonas aeruginosa is not a likely causative agent. Gentamicin, tobramycin, and amikacin are effective against a broad spectrum of gram-negative organisms including P. aeruginosa. In general, both gentamicin and tobramycin are more active in vitro than amikacin on a weight basis; however, higher serum levels are achievable with amikacin than with the two others. Amikacin is probably the aminoglycoside of first choice when gentamicin resistance is strongly suspected.

Amikacin↗
PubMed1986

Ciprofloxacin: a comparative evaluation of its bactericidal activity in human serum against four enterobacterial species.

Serum bactericidal titres following a 200 mg i.v. dose of ciprofloxacin were measured in healthy volunteers and compared with those achieved with standard doses of ceftazidime, piperacillin and gentamicin, given alone or in combination. Five strains of each of four enterobacterial species were included in the study. Bactericidal titres 1 h after infusion of ciprofloxacin exceeded 1:16 for Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris and Enterobacter cloacae. While ceftazidime produced higher peak bactericidal titres against the Enterobacteriaceae, piperacillin was less effective than ciprofloxacin against three of the four enterobacterial species tested. Among the combinations, only piperacillin/gentamicin showed synergistic activity against some strains. Studies of bacterial killing kinetics again confirmed the high bactericidal activity of ciprofloxacin for the Enterobacteriaceae. The combination of ciprofloxacin with gentamicin resulted in more rapid killing of some strains of Klebsiella pneumoniae and Proteus vulgaris.

Adult↗
PubMed1986

[Degradation of the insecticide parathion in soil].

Degradation of the insecticide Parathion in four types of soil from the Northeast of Brazil has been studied using radiometric techniques. In all the soil samples, sterilized or not, metabolites were detected with Rf values of 0.00 and 0.17 respectively--Silica Gel 60 F254 tlc plates (Merck); solvent system: hexane-acetone (4:1, v/v)--. However, 14CO2 was formed only with the non-sterilized soils and this was independent of the use or not of organic fertilizer. These results suggest that the two metabolites, mentioned above, are formed by a predominantly non-biological pathway, where as the formation of carbon dioxide requires the participation of the microbial flora of the soil. Analysis of the interaction of 14C-Parathion with soils shows that the extent of degradation of this insecticide is modified by adsorption on the soil particles.

Adsorption↗
PubMed1985

[Bacteriostatic and bactericidal effect of cefotaxime combinations on Staphylococcus aureus assessed by FIC and FBC-index determination].

Activity of cefotaxime associated with one of nine other antibiotics (amikacin, dibekacin, gentamicin, netilmicin, sisomicin, tobramycin, erythromycin, clindamycin, and chloramphenicol) was studied by a checkerboard method with determination of FIC and FBC-indices. Four S. aureus strains were used: one homogeneous methicillin-resistant strain (S1), one heterogeneous methicillin-resistant strain (S2), and two susceptible strains (S3 and S4). Strong synergism between cefotaxime and aminoglycosides was found only for S2, with no significant differences between aminoglycosides (index # 0.3). Cefotaxime and chloramphenicol showed synergistic or additive bacteriostatic activities and consistently antagonist bactericidal activities. Bactericidal activities of cefotaxime and erythromycin were likewise antagonistic, whereas cefotaxime and clindamycin occasionally exhibited in vitro synergism.

Aminoglycosides↗
PubMed1976

[Experimental study of an aerosol preparation containing gentamicin (gentasol)].

Composition of a suspension aerosol drug, gentasol for local application was developed. It contained gentamycin and prednisolon. The antimicrobial properties of the drug were studied in vitro. It was found that gentasol had a pronounced antimicrobiol effect and inhibited the growth of many microorganisms including cultures resistant to other antibiotics. The drug was active against Ps. aeruginosa and Proteus, which is an advantage of it as compared to other antibiotic aerosol drugs. The study showed that gentasol had self-sterilizing properties.

Aerosols↗
PubMed1992

On the possibility of chemosynthetic ecosystems in subsurface habitats on Mars.

We have reexamined the question of extant microbial life on Mars in light of the most recent information about the planet and recently discovered nonphotosynthetic microbial ecosystems on Earth--deep sea hydrothermal vent communities and deep subsurface aquifer communities. On Mars, protected subsurface niches associated with hydrothermal activity could have continued to support life even after surface conditions became inhospitable. Geochemical evidence from the SNC meteorites and geomorphological evidence for recent volcanism suggest that such habitats could persist to the present time. There are also extensive geological features that attest to the ubiquitous nature of volcano-ground ice interactions on Mars. We suggest a possible deep subsurface microbial ecology similar to those discovered to depths of several kilometers below the surface of the Earth. We focus on anaerobic systems utilizing CO2 as the primary source of carbon. Liquid water could be provided by the heat of geothermal or volcanic activity melting permafrost or other subsurface water sources. Gases from volcanic activity deep in the planet could provide reducing power (as CH4, H2, or H2S) percolating up from below and enabling the development of a microbial community based upon chemolithoautotrophy. We suggest a methanogen (or acetogen) and sulfur-based microbial ecology as one possible basis for microbial primary production. Our hypothetical ecosystem is neither supported, nor excluded, by current observations of Mars. Tests for such a subsurface system involve locating active geothermal areas associated with ground ice or detecting trace quantities of reduced atmospheric gases that would leak from such a system.

Carbon Dioxide↗
PubMed1983

[Interaction of Acholeplasma laidlawii and Mycoplasma arthritidis with the lymphocytes of mice of different strains].

The interaction of mycoplasmas and mouse lymphocytes has been studied by the microbiological and electron-microscopic methods. The experiments have shown that A. laidlawii and M. arthritidis are adsorbed on lymphocytes and thymocytes of (C57BL6 X A/He)F1, BALB and C57BL mice after 15 minutes of their joint incubation at 37 degrees C, 1 hour later adsorption reaches its maximum intensity and after further prolongation of the time of incubation the number of adsorbed microbial cells remains unchanged. The first stage of the interaction of mycoplasmas with splenic and thymic lymphocytes (adsorption) is the same in (C57BL6 X X A/He)F1, BALB and C57BL mice, and differences in the persistence of mycoplasmas in mice of the above strains are probably due not to different capacity of the cells for adsorbing mycoplasmas, but to differences in the immune status of these animals.

Acholeplasma laidlawii↗
PubMed1991

A host-host-pathogen model with free-living infective stages, applicable to microbial pest control.

A model has been investigated of the dynamics of the interaction between two hosts which are both attacked by a common pathogen, where the pathogen has free-living infective stages the population size of which must itself be modelled explicitly, and where the host species do not interact with one another except through their shared pathogen. If either host interacted with the pathogen alone, three broad classes of dynamics would be possible: host regulation, pathogen persistence and pathogen extinction. Here, all possible types of combinations of hosts are examined: regulation-regulation (both hosts would be regulated if they interacted with the pathogen alone), regulation-persistence, regulation-extinction, persistence-persistence persistence-extinction and extinction-extinction. A wide range of dynamics is generated, including a number of patterns quite unlike those found in the one-host pathogen case (e.g. persistence in one host, elimination of the other host) and behaviour contingent on initial densities in the system. For clarity and pertinence, attention is focused on the case where one host is a pest, the pathogen is a potential microbial control agent, and the other host is a non-target species which it is undesirable to harm. The model suggests, broadly, that non-targets are unlikely to be seriously threatened in such cases, and also that non-targets, far from undermining pest control, are quite likely to contribute to its efficacy.

Animals↗
PubMed1999

Role of fibronectin-binding MSCRAMMs in bacterial adherence and entry into mammalian cells.

Most bacterial infections are initiated by the adherence of microorganisms to host tissues. This process involves the interaction of specific bacterial surface structures, called adhesins, with host components. In this review, we discuss a group of microbial adhesins known as Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMs) which recognize and bind FN. The interaction of bacteria with FN is believed to contribute significantly to the virulence of a number of microorganisms, including staphylococci and streptococci. Several FN-binding MSCRAMMs of staphylococci and streptococci exhibit a similar structural organization and mechanism of ligand recognition. The ligand-binding domain consists of tandem repeats of a approximately 45 amino acid long unit which bind to the 29-kDa N-terminal region of FN. The binding mechanism is unusual in that the repeat units are unstructured and appear to undergo a conformational change upon ligand binding. Apart from supporting bacterial adherence, FN is also involved in bacterial entry into non-phagocytic mammalian cells. A sandwich model has been proposed in which FN forms a molecular bridge between MSCRAMMs on the bacterial surface and integrins on the host cell. However, the precise mechanism of bacterial invasion and the roles of FN and integrins in this process have yet to be fully elucidated.

Adhesins, Bacterial↗
PubMed1995

Functional interaction of ligands and receptors of the hematopoietic superfamily in yeast.

Circulating peptide hormones and growth factors interact with cell surface receptors to initiate specific cellular responses. These complexes can consist of a simple association between two proteins or a more elaborate association of multiple proteins. We describe the functional expression of ligands and corresponding receptors in a microbial system useful for the rapid dissection of these important protein interactions. GH or PRL and extracellular domains of their respective receptors were functionally expressed as fusion proteins in an extended two-hybrid protein-protein interaction system. Reversible and specific ligand-receptor interactions were demonstrated by concurrent expression of free ligand peptides (GH or PRL) as binding competitors. The versatility established by expressing three heterologous proteins allowed for the investigation of higher order structures. Ligand-dependent GH receptor dimerization was demonstrated but PRL receptor dimerization was not observed in an analogous assay, suggesting that these related growth factors may not engage receptors in a similar manner. Additionally, significant association of GH receptors was observed in the absence of ligand, suggesting that there may be substantial avidity between these receptor proteins before ligand binding. Ligand-dependent and ligand-independent receptor dimerization was demonstrated by vascular endothelial growth factor and receptor proteins in similar assays. These findings indicate that extracellular protein interactions such as ligand-receptor association, as well as the formation of higher order protein structures important for the activation of hematopoietic receptors, can be rapidly investigated in this microbial expression system.

Binding, Competitive↗