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At least 1,441 records · Page 80Linked to original sources
PubMed2000

Molecular cloning of cDNA encoding alpha-N-acetylgalactosaminidase from Acremonium sp. and its expression in yeast.

Alpha-N-acetylgalactosaminidase (alpha-GalNAc-ase; EC 3.2.1.49) is an exoglycosidase specific for the hydrolysis of terminal alpha-linked N-acetylgalactosamine in various sugar chains. The cDNA, nagA, encoding alpha-GalNAc-ase from Acremonium sp. was cloned, sequenced, and expressed in yeast Saccharomyces cerevisiae. The nagA contains an open reading frame which encodes for 547 amino acid residues including 21 residues of a signal peptide in its N-terminal. The calculated molecular mass of mature protein from the deduced amino acid sequence of nagA is 57260 Da, which corresponds to the value obtained from SDS-PAGE of native and recombinant enzymes treated with endo-beta-N-acetylglucosaminidase H. The amino acid sequence of NagA showed significant similarity to those of eukaryotic alpha-GalNAc-ases and alpha-galactosidases (alpha-Gal-ases), particularly alpha-Gal-ase A (AglA) from Aspergillus niger. Phylogenetic analysis revealed that NagA does not belong to the cluster of vertebrate alpha-GalNAc-ase and alpha-Gal-ase but forms another cluster with AglA and yeast alpha-Gal-ases. Thus, the evolutionary origin of the fungal alpha-GalNAc-ase is suggested to be different from that of vertebrate alpha-GalNAc-ase. This is the first report of a microbial alpha-GalNAc-ase gene.

Acremonium↗
PubMed2002

Laser--Raman imagery of Earth's earliest fossils.

Unlike the familiar Phanerozoic history of life, evolution during the earlier and much longer Precambrian segment of geological time centred on prokaryotic microbes. Because such microorganisms are minute, are preserved incompletely in geological materials, and have simple morphologies that can be mimicked by nonbiological mineral microstructures, discriminating between true microbial fossils and microscopic pseudofossil 'lookalikes' can be difficult. Thus, valid identification of fossil microbes, which is essential to understanding the prokaryote-dominated, Precambrian 85% of life's history, can require more than traditional palaeontology that is focused on morphology. By combining optically discernible morphology with analyses of chemical composition, laser--Raman spectroscopic imagery of individual microscopic fossils provides a means by which to address this need. Here we apply this technique to exceptionally ancient fossil microbe-like objects, including the oldest such specimens reported from the geological record, and show that the results obtained substantiate the biological origin of the earliest cellular fossils known.

Archaea↗
PubMedDate not supplied

New trends in regulatory rules and surveillance of antimicrobial resistance in bacteria of animal origin.

Since the introduction in the 1940s of antibiotics as drugs against bacterial infections in human and then veterinary medicine, two major events have caused a shift in the antibiotherapy era: (1) the emergence of resistant bacteria and (2) the awareness of the limits of new drug development. It rapidly became urgent to set up measures in order to evaluate the importance of resistant bacteria and their origin as well as to limit the dissemination of resistant vectors (bacteria and bacterial genes). This led to the establishment of guidelines and regulatory rules necessary for risk assessment and clearly dependent upon monitoring and research organisations. At a veterinary level, the possible dissemination of multiresistant bacteria from animals to humans, through feeding, urged various national European and international institutions to give general recommendations to monitor and contain the emergence and diffusion of resistant strains. This paper gives an overview of the evolution of regulatory rules and monitoring systems dealing with multiresistant bacteria.

Animal Diseases↗
PubMed2000

Evolutionary reversals during viral adaptation to alternating hosts.

Experimental adaptation of the bacteriophage phiX174 to a Salmonella host depressed its ability to grow on the traditional Escherichia host, whereas adaptation to Escherichia did not appreciably affect growth on Salmonella. Continued host switching consistently exhibited this pattern. Growth inhibition on Escherichia resulted from two to three substitutions in the major capsid gene. When these phages were forced to grow again on Escherichia, fitness recovery occurred predominantly by reversions at these same sites, rather than by second-site compensatory changes, the more frequently observed mechanism in most microbial systems. The affected residues lie on the virion surface and they alter attachment efficiency, yet they occur in a region distinct from a putative binding region previously identified from X-ray crystallography. These residues not only experienced high rates of evolution in our experiments, but also exhibited high levels of radical amino acid variation among phiX174 and its known relatives, consistent with a history of adaptation involving these sites.

Adaptation, Physiological↗
PubMed2000

Evolution of lamivudine-resistant hepatitis B virus and HIV-1 in co-infected individuals: an analysis of the CAESAR study. CAESAR co-ordinating committee.

OBJECTIVES: Lamivudine has potent activity against HIV-1 and hepatitis B virus (HBV). Co-infection with these two viruses is common, and this may therefore influence the choice of antiretroviral therapies. A cohort of co-infected patients treated with lamivudine were studied in order to evaluate the differential effects of lamivudine on the two viral populations within the same individual after 44-52 weeks of therapy. DESIGN AND METHODS: Retrospective virological analysis of an HIV-1/HBV co-infected lamivudine cohort derived from a randomized, placebo-controlled study of lamivudine in HIV infection, the CAESAR study. RESULTS: Five of thirteen patients with HBV viral load > 10,000 copies/ml after 44-52 weeks of lamivudine therapy had genotypic drug resistance. Four of these five had a rebound of viral replication over the period of study and in one case this was associated with an alanine transaminase serum elevation. Ten of the thirteen patients had a 44-52 week HIV viral load > 1000 copies/ml, all of whom also had HIV reverse transcriptase M184V or M184I mutations. CONCLUSIONS: Extrapolating these results to the population yields an estimated 1-year incidence of drug-resistant HBV of at least 14% in lamivudine-treated HIV-1/HBV co-infected patients. The clinical and virological benefit of HBV lamivudine monotherapy in co-infected patients should be balanced against the potential for emergence of drug resistance. Further, these data suggest that the determinants of HIV and HBV drug resistance are different and that parallel evolution, rather than co-evolution of HBV and HIV-1 in co-infected individuals occurs.

CD4 Lymphocyte Count↗
PubMed2003

Global analysis of river systems: from Earth system controls to Anthropocene syndromes.

Continental aquatic systems from rivers to the coastal zone are considered within two perspectives: (i) as a major link between the atmosphere, pedosphere, biosphere and oceans within the Earth system with its Holocene dynamics, and (ii) as water and aquatic biota resources progressively used and transformed by humans. Human pressures have now reached a state where the continental aquatic systems can no longer be considered as being controlled by only Earth system processes, thus defining a new era, the Anthropocene. Riverine changes, now observed at the global scale, are described through a first set of syndromes (flood regulation, fragmentation, sediment imbalance, neo-arheism, salinization, chemical contamination, acidification, eutrophication and microbial contamination) with their related causes and symptoms. These syndromes have direct influences on water uses, either positive or negative. They also modify some Earth system key functions such as sediment, water, nutrient and carbon balances, greenhouse gas emissions and aquatic biodiversity. Evolution of river syndromes over the past 2000 years is complex: it depends upon the stages of regional human development and on natural conditions, as illustrated here for the chemical contamination syndrome. River damming, eutrophication and generalized decrease of river flow due to irrigation are some of the other global features of river changes. Future management of river systems should also consider these long-term impacts on the Earth system.

Biodiversity↗
PubMed1988

Chromosomal gene transfer in Spiroplasma citri.

The study of resistance marker rearrangement in Spiroplasma citri mutants provides evidence of transfer of chromosomal information followed by recombination. This is the first report of such a transfer in vivo in the mollicutes--that is, in the smallest self-replicating organisms. The double-resistant phenotypes obtained are stable even without selection pressure. The mechanism of gene transfer is insensitive to deoxyribonuclease, requires contact, and possibly, areas of fusion of the cell membranes; it shares properties with the transfer by protoplast fusion in Gram-positive bacteria. The extensive degenerative evolution of mollicutes has retained, in S. citri, bacterial functions of chromosomal transfer and recombination.

Arsenates↗
PubMed2006

Fitness costs of fluoroquinolone resistance in Streptococcus pneumoniae.

The fitness cost of the genes responsible for resistance to fluoroquinolones in clinical isolates of Streptococcus pneumoniae were estimated in vitro in a common genetic background. Naturally occurring parC, parE, and gyrA loci containing mutations in the quinolone-resistance-determining regions were introduced by transformation into S. pneumoniae strain R6 individually and in combinations. The fitness of these transformants was estimated by pairwise competition experiments with a common R6 strain. On average, single par and gyr mutants responsible for low-level MIC resistance (first-step resistance) impose a fitness burden of approximately 8%. Some of these mutants engender no measurable cost, while one, a parE mutant, reduces the fitness of these bacteria by more than 40%. Most interestingly, the addition of the second par or gyr mutations required for clinically significant, high-MIC fluoroquinolone resistance does not increase the fitness burden imposed by these single genes and can even reduce it. We discuss the implications of these results for the epidemiology of fluoroquinolone resistance and the evolution of acquired resistance in treated patients.

DNA Gyrase↗
PubMed1995

PCR mapping of integrons reveals several novel combinations of resistance genes.

The integron is a new type of mobile element which has evolved by a site-specific recombinational mechanism. Integrons consist of two conserved segments of DNA separated by a variable region containing one or more genes integrated as cassettes. Oligonucleotide probes specific for the conserved segments have revealed that integrons are widespread in recently isolated clinical bacteria. Also, by using oligonucleotide probes for several antibiotic resistance genes, we have found novel combinations of resistance genes in these strains. By using PCR, we have determined the content and order of the resistance genes inserted between the conserved segments in the integrons of these clinical isolates. PCR mapping of integrons can be a useful epidemiological tool to study the evolution of multiresistance plasmids and transposons and dissemination of antibiotic resistance genes.

Base Sequence↗
PubMed2000

Effects of the movement of insertion sequences on the structure of VanA glycopeptide resistance elements in Enterococcus faecium.

A Tn1546-related element with IS1216V at position 8839 underwent a structural change after storage of the host strain of Enterococcus faecium at 4 degrees C. The element acquired IS1542 at position 3932, nucleotides 8732 to 8831 were deleted, and the first 3417 nucleotides were lost and replaced by an inverted copy of the IS1216V-vanY-vanZ-inverted-repeat block from the 3' end. Insertion sequence movement is likely to play a key role in the evolution of VanA resistance elements.

Anti-Bacterial Agents↗
PubMed2004

Diverse tetracycline resistance genotypes of Megasphaera elsdenii strains selectively cultured from swine feces.

A total of 30 Megasphaera elsdenii strains, selectively isolated from the feces of organically raised swine by using Me109 M medium, and one bovine strain were analyzed for tetracycline resistance genotypic and phenotypic traits. Tetracycline-resistant strains carried tet(O), tet(W), or a tet gene mosaic of tet(O) and tet(W). M. elsdenii strains carrying tet(OWO) genes exhibited the highest tetracycline MICs (128 to >256 microg/ml), suggesting that tet(O)-tet(W) mosaic genes provide the selective advantage of greater tetracycline resistance for this species. Seven tet genotypes are now known for M. elsdenii, an archetype commensal anaerobe and model for tet gene evolution in the mammalian intestinal tract.

Animals↗
PubMed1993

[Incidence of tuberculostatic-resistant Mycobacterium tuberculosis. Clinical aspects and impact on therapy and clinical course].

BACKGROUND: To know the incidence of Mycobacterium tuberculosis resistant to anti-tuberculin drugs in addition to the clinical features, treatment and evolution of the patients. METHODS: This was a retrospective study of the clinical histories of patients with isolation of Mycobacterium tuberculosis with some type of resistance studied from January 1980 to April 1992. RESULTS: During the period studied 470 patients were diagnosed with tuberculosis by cultures. In 30 of these cases (6.4%) Mycobacterium tuberculosis resistant to Isoniazide (8), Streptomycin (6), Isoniazide + Rifampicin (4), Isoniazide + Streptomycin (3), Isoniazide + Ethambutol (2), Isoniazide + Rifampicin + Streptomycin (2), Isoniazide + Rifampicin + Ethambutol (2), Rifampicin (1), Ethambutol (1), Isoniazide + Pyrazinamide (1) and Isoniazide + Rifampicin + Streptomycin + Ethambutol (1) were isolated. Clinical information was obtained on 23 patients, with the most frequent clinical pictures being those of respiratory infection (15). Five cases occurred in HIV+ patients. The resistance was considered as primary in 58.97% of the cases with modifications in empiric treatment being necessary in 6 cases. In 15 out of the 19 patients from whom the data of the follow up was obtained the evolution was good. CONCLUSIONS: Resistance to Mycobacterium tuberculosis was 6.4%, with the high number of strains resistant to Rifampicin being of note. In 79% of the cases in which follow up data was obtained the resistance had no impact on treatment due to the good evolution of the patients in relation with the treatment used.

Adult↗
PubMed1976

Primary resistence of mycobacteria in tuberculosis patients.

Primary mycobactria resistance especially in some countries may be a serious obstacle to a successful therapy and the number of patients carrier of primary resistant mycobacteria remains almost at the same level in spite of the chemotherapeutic treatments and the usually rapid recover of the newly diagnosed cases. This may probably be attributed to the fact that the number of chronic patients, spitting resistant tubercle bacilli has remained almost the same, because these patients are eliminated little by little. In our country there is a constant regression of the morbidity, but not so rapid as expected, The newly diagnosed patients are generally young and, if well treated, they heal quickly and well; moreover, they are usually not so richly bacillised as they used to be once and the severity of their disease, globally evaluated, appears also reduced. The cultural positivity at the first admission into hospital is also diminishing. From all the above facts it is obvious that in order to eradicate tuberculosis it is necessary: First - to avoid creatin chronic patients; in order to reach this goal the treatment must be the most effective possible from the very beginning: INH and Rifampin. Second - to try to cure the chronic patients and to render them abacillary of, at least, to treat them intensively, with the purpose of inducing in the infecting flora a polyresistance which reners the mycobacteria hypovirulent, especially if it includes a R/AMP resistance over 40-gamma. Third - the role of the primary resistance in the epidemiology and the evolution of tuberculosis in the various countries and in the single patients, may be very different.

Adolescent↗
PubMedDate not supplied

[The evolution of the clinical course of infectious endocarditis].

As many as 188 records of IE patients were studied as were 67 autopsies of deceased persons. Significant changes in the clinical course of IE were disclosed over the past 10-15 years versus previous 15: more prominent role of staphylococcal and gram-negative flora in the etiology of the illness, with microbial associations-caused IE cases having become more common. Diagnostic value of hemoculture did not appear to show much promise. The following items were found to be important risk factors for IE: prior viral and bacterial infection, invasive interventions, and chronic somatic diseases. There prevailed those IE forms having appeared on the intact heart valves in elderly persons and those at a mature age. In the course of the illness there tended to be more toxic and allergic manifestations, thromboembolic complications, and extensive vascular pathology.

Adolescent↗
PubMedDate not supplied

[Effect of biological activation on the evolution of microflora during composting of urban waste].

In two solid urban wastes piles, one treated with 7.5% of good bovine manure, the other used as a test, the evolution of the microflora has been studied, during the first period of biodegradation and at the end of the maturation process, in order to control if bioactivation can positively affect the biodegradation development. Actinomytcetes and fungi have been examined, and the following functional microbial groups: aerobic nitrogen fixing bacteria, ammonia bacteria, proteolytics, nitrosants, nitricants, aerobic cellulolytics, amilolytics, pectinolytics. During the process, no significant quantitative difference between the microflora of the two piles was found, except for aerobic cellulolytic, which were strongly superior in number in the end product from the bioactivated pile.

Bacteria↗