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At least 109 records · Page 6Linked to original sources
PubMed2006

Bacterial populations as perfect gases: genomic integrity and diversification tensions in Helicobacter pylori.

Microorganisms that persist in single hosts face particular challenges. Helicobacter pylori, an obligate bacterial parasite of the human stomach, has evolved a lifestyle that features interstrain competition and intraspecies cooperation, both of which involve horizontal gene transfer. Microbial species must maintain genomic integrity, yet H. pylori has evolved a complex nonlinear system for diversification that exists in dynamic tension with the mechanisms for ensuring fidelity. Here, we review these tensions and propose that they create a dynamic pool of genetic variants that is sufficiently genetically diverse to allow H. pylori to occupy all of the potential niches in the stomach.

Biological Evolution↗
PubMed2002

Optimal testing conditions for determining MICs and minimum fungicidal concentrations of new and established antifungal agents for uncommon molds: NCCLS collaborative study.

This collaborative three-center study evaluated NCCLS M38-A document testing conditions and other testing conditions for the antifungal susceptibility testing of 35 isolates of Aspergillus nidulans, A. terreus, Bipolaris hawaiiensis, B. spicifera, Cladophialophora bantiana, Dactylaria constricta, Fusarium solani, Paecilomyces lilacinus, Scedosporium prolificans, Trichoderma longibrachiatum, and Wangiella dermatitidis for itraconazole, three new triazoles (voriconazole, posaconazole, and ravuconazole), and amphotericin B. MICs and minimum fungicidal concentrations (MFCs) were determined in each center by using four media (standard RPMI-1640 [RPMI], RPMI with 2% dextrose [RPMI-2%], antibiotic medium 3 [M3], and M3 with 2% dextrose [M3-2%]) and two criteria of MIC determination (complete growth inhibition [MICs-0] and prominent growth inhibition [MICs-2]) at 24, 48 and 72 h. MFCs were defined as the lowest drug concentrations that yielded <3 colonies (approximately 99 to 99.5% killing activity). The reproducibility (within three wells) was higher among MICs-0 (93 to 99%) with either RPMI or M3 media than among all MICs-2 (86 to 95%) for the five agents at 48 to 72 h. The agreement for MFCs was lower (86 to 94%). Based on interlaboratory agreement, the optimal testing conditions were RPMI broth, 48 to 72 h of incubation and 100% growth inhibition (MIC-0); MFCs can be obtained after MIC determination with the above optimal testing parameters. These results warrant consideration for inclusion in the future version of the NCCLS M38 document. However, the role of these in vitro values as predictors of clinical outcome remains to be established in clinical trials.

Amphotericin B↗
PubMed2003

Quality control limits for fluconazole disk susceptibility tests on Mueller-Hinton agar with glucose and methylene blue.

An international collaborative study was performed in order to propose quality control limits for fluconazole disk diffusion susceptibility tests on Mueller-Hinton agar with 2% glucose and 0.5 micro g of methylene blue per ml. The supplements may be added before autoclaving the agar, or Mueller-Hinton agar plates may be flooded with a glucose-methylene blue solution. Replicate tests on both types of agar plates generated data to propose zone size limits for tests of Candida parapsilosis ATCC 22019 (22 to 33 mm), C. tropicalis ATCC 750 (26 to 37 mm), and C. albicans ATCC 90028 (28 to 39 mm). C. krusei ATCC 6258 was not useful for this purpose.

Agar↗
PubMed2004

Quality control limits for voriconazole disk susceptibility tests on Mueller-Hinton agar with glucose and methylene blue.

An international collaborative study was performed in order to propose quality control limits for voriconazole disk diffusion tests on Mueller-Hinton agar with 2% glucose and 0.5 micro g of methylene blue per ml. The supplement may be added to the agar before autoclaving, or Mueller-Hinton agar plates may be flooded with a glucose-methylene blue solution. Replicate tests on both types of agar plates with 1- micro g voriconazole disks generated data to propose zone size limits for tests of Candida parapsilosis ATCC 22019 (28 to 37 mm), Candida albicans ATCC 90028 (31 to 42 mm), and Candida krusei ATCC 6258 (16 to 25 mm). Candida tropicalis ATCC 750 was not useful for this purpose.

Agar↗
PubMed2000

Standardization of antituberculosis drug resistance surveillance in Europe. Recommendations of a World Health Organization (WHO) and International Union Against Tuberculosis and Lung Disease (IUATLD) Working Group.

Surveillance of antituberculosis drug resistance is an essential tool for evaluating the quality of tuberculosis control programmes. Consensus-based recommendations on uniform reporting of antituberculosis drug resistance surveillance data in Europe have been developed by a Working Group of the World Health Organization (WHO) and the International Union Against Tuberculosis and Lung Disease (IUATLD). Laboratories should use standardized methods for testing drug susceptibility with a quality assurance programme including national and international proficiency testing. The proportion of drug resistance, particularly resistance to isoniazid, rifampicin or both (multidrug resistance) among all definite, i.e. culture-positive, tuberculosis cases at the start of treatment is the major indicator of interest. It should be calculated separately among patients treated previously and among those who have never been treated with > or = 1 month of combined antituberculosis drugs. The Working Group recommends that, in countries in which resources allow, laboratories report drug susceptibility test results on all isolates of the Mycobacterium tuberculosis complex. Test results of the specimen at the start of treatment and clinical data from the notification should be linked using a suitable identifier. Results should be presented by calendar year and analysed by age, sex, place of birth, site of disease and sputum smear results. In countries in which a routine system cannot be organized, representative surveys or sentinel systems are possible alternatives. In some countries, the annual prevalence of multidrug-resistant tuberculosis may be estimated through a national laboratory reporting system.

Antitubercular Agents↗
PubMed1997

Epidemiological approach to the prevention of imported infectious diseases in the age of globalization.

As globalization progresses, over 10% of Japanese citizens now travel abroad. With this, there are many cases in which people catch a variety of infectious and contagious diseases abroad. In addition, new infectious diseases also have been emerging in the world. Therefore, protection of travelers' health and prevention of the import of infectious diseases are of ever increasing importance. From this point of view, at the Narita Airport Quarantine Station, a Health Information Corner for travelers going abroad was established in 1992, along with Health Consultation Rooms for arriving passengers. In order to overcome imported infectious diseases, the promotion of domestic and international cooperation among the health and medical organizations concerned is required for primary prevention, and early detection or treatment of the diseases.

Cholera↗
PubMed2000

Antibiotic use in developing countries.

Antimicrobials have been used successfully for over 6 decades, but genes expressing resistance to them have emerged in strains of bacteria and have disseminated through the global ecosystem to reach infecting microorganisms, produce disease, and seriously interfere with therapy, allowing infections to progress and kill despite antibiotic administration. The upsurge in prevalence of such resistance genes in the bacterial population that colonize and infect humans involves two processes, emergence and dissemination, in both of which there have been contributions from the developing world, where resistance is common and increasing. The emergence of pneumococcal isolates noted in Papua New Guinea and later in South Africa that 1 decade later spread to most of the world and the intercontinental spread between the United States and Venezuela of a new gentamicin resistance gene carried on an epidemic plasmid are examples of the ability of bacteria to travel freely, without regard to borders. Complex societal issues such as the misuse of antibiotics by physicians, pharmacists, and the public; the suboptimal quality of the drugs (emergence); and conditions such as crowding, lack of hygiene, poor or nonexistent hospital infection control practices, or insufficient surveillance (dissemination) play a largely unmeasured role that requires study and solutions. In the meantime, we may intervene to delay the emergence of resistance and to limit its spread by promoting the judicious use of antibiotics both at the local level as well as from multinational organized cooperative efforts. Education and improvement of surveillance and socioeconomic conditions are integral parts of any solution strategy.

Anti-Bacterial Agents↗
PubMed2003

Dendritic cell-induced autoimmune heart failure requires cooperation between adaptive and innate immunity.

Genetic susceptibility and autoimmunity triggered by microbial infections are factors implicated in the pathogenesis of dilated cardiomyopathy, the most common cause of heart failure in young patients. Here we show that dendritic cells (DCs) loaded with a heart-specific self peptide induce CD4+ T-cell-mediated myocarditis in nontransgenic mice. Toll-like receptor (TLR) stimulation, in concert with CD40 triggering of self peptide-loaded dendritic cells, was shown to be required for disease induction. After resolution of acute myocarditis, DC-immunized mice developed heart failure, and TLR stimulation of these mice resulted in relapse of inflammatory infiltrates. Injection of damaged, syngeneic cardiomyocytes also induced myocarditis in mice if TLRs were activated in vivo. DC-induced myocarditis provides a unifying theory as to how tissue damage and activation of TLRs during infection can induce autoimmunity, relapses and cardiomyopathy.

Adaptation, Physiological↗
PubMed2005

Aspartate transcarbamylase from the hyperthermophilic archaeon Pyrococcus abyssi. Insights into cooperative and allosteric mechanisms.

Aspartate transcarbamylase (ATCase) (EC 2.1.3.2) from the hyperthermophilic archaeon Pyrococcus abyssi was purified from recombinant Escherichia coli cells. The enzyme has the molecular organization of class B microbial aspartate transcarbamylases whose prototype is the E. coli enzyme. P. abyssi ATCase is cooperative towards aspartate. Despite constraints imposed by adaptation to high temperature, the transition between T- and R-states involves significant changes in the quaternary structure, which were detected by analytical ultracentrifugation. The enzyme is allosterically regulated by ATP (activator) and by CTP and UTP (inhibitors). Nucleotide competition experiments showed that these effectors compete for the same sites. At least two regulatory properties distinguish P. abyssi ATCase from E. coli ATCase: (a) UTP by itself is an inhibitor; (b) whereas ATP and UTP act at millimolar concentrations, CTP inhibits at micromolar concentrations, suggesting that in P. abyssi, inhibition by CTP is the major control of enzyme activity. While V(max) increased with temperature, cooperative and allosteric effects were little or not affected, showing that molecular adaptation to high temperature allows the flexibility required to form the appropriate networks of interactions. In contrast to the same enzyme in P. abyssi cellular extracts, the pure enzyme is inhibited by the carbamyl phosphate analogue phosphonacetate; this difference supports the idea that in native cells ATCase interacts with carbamyl phosphate synthetase to channel the highly thermolabile carbamyl phosphate.

Adenosine Triphosphate↗
PubMed1998

Cooperative organization of bacterial colonies: from genotype to morphotype.

In nature, bacteria must often cope with difficult environmental conditions. To do so they have developed sophisticated cooperative behavior and intricate communication pathways. Utilizing these elements, motile microbial colonies frequently develop complex patterns in response to adverse growth conditions on hard surfaces under conditions of energy limitation. We employ the term morphotype to refer to specific properties of colonial development. The morphologies we discuss include a tip-splitting (T) morphotype, chiral (C) morphotype, and vortex (V) morphotype. A generic modeling approach was developed by combining a detailed study of the cellular behavior and dynamics during colonial development and invoking concepts derived from the study of pattern formation in nonliving systems. Analysis of patterning behavior of the models suggests bacterial processes whereby communication leads to self-organization by using cooperative cellular interactions. New features emerging from the model include various models of cell-cell signaling, such as long-range chemorepulsion, short-range chemoattraction, and, in the case of the V morphotype, rotational chemotaxis. In this regard, pattern formation in microorganisms can be viewed as the result of the exchange of information between the micro-level (the individual cells) and the macro-level (the colony).

Bacteria↗
PubMed1991

Allergic manifestations of human immunodeficiency virus (HIV) infection.

Drug allergy is the most common and significant allergic manifestation of HIV3 infection. Initially described in patients treated with SMX-TMP for PCP, allergy is now known to involve a multitude of drugs. The pathogenesis of, and risk factors for, allergy in HIV infection are poorly understood, although there is evidence suggesting that allergy is more common with advancing immunodeficiency. HIV-negative subjects with sulfonamide allergy may have drug-specific antibodies and drug metabolite-induced lymphocyte cytotoxicity, abnormalities that could partly explain the allergic mechanisms and which may have future diagnostic potential; these abnormalities have not been described in HIV-infected subjects. Therapy includes avoidance, suppressive agents such as corticosteroids, and desensitization, although the appropriate role for each is not entirely clear. Serum IgE levels have been shown to rise with progressive disease; those patients with higher levels may have a worse prognosis. The mechanisms of this rise are multifactorial, probably a combination of altered T-lymphocyte regulation of IgE synthesis and of production of specific IgE directed against microbial antigens.

Acquired Immunodeficiency Syndrome↗