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PubMed2002

The relation between sale of antimicrobial drugs and antibiotic resistance in uropathogens in general practice.

BACKGROUND: Overuse of antimicrobial drugs has resulted in an alarming increase in bacterial resistance in most countries. The relevance for general practice is unknown. OBJECTIVE: To evaluate the impact of the sale of antimicrobial drugs on bacterial resistance as found in uropathogens from general practice. SETTING: General practice in Belgium and Norway. METHODS: Observational study. RESULTS: The sale of antimicrobial drugs indicated for use in the treatment of urinary tract infection was four times higher in Belgium than in Norway (18.5 vs 4.4 DDD/1000 inhabitants/day). The antibiotic resistance reported by microbiological laboratories as valid for general practice was significant higher in Belgium than in Norway (ampicillins (44% vs 27%), co-trimoxazole (28% vs 17%), fluoroquinolones (12% vs 2%) and nitrofurantoin (16% vs 11%, p < 0.0001 for all). However, the antibiotic resistance found in urine samples from dysuric women in general practice was similar (trimethoprim 14% vs 12%, co-trimoxazole 14% vs 11%, nitrofurantoin 7% vs 3%), except in the case of ampicillins (30% vs 19%, p < 0.05). CONCLUSION: The impact of the antimicrobial sale on resistance in uropathogens seems less than expected at the general practice level, even though local microbiological reports mention fairly high antibiotic resistance data. Adapted methods for following-up bacterial resistance evolution in general practice are needed.

Acute Disease↗
PubMed2003

Tírez lake as a terrestrial analog of Europa.

Tírez Lake (La Mancha, central Spain) is proposed as a terrestrial analogue of Europa's ocean. The proposal is based on the comparison of the hydrogeochemistry of Tírez Lake with the geochemical features of the alteration mineralogy of meteoritic precursors and with Galileo's Near Infrared Mapping Spectrometer data on Europa's surface. To validate the astrobiological potential of Tírez Lake as an analog of Europa, different hydrogeochemical, mineral, and microbial analyses were performed. Experimental and theoretical modeling helped to understand the crystallization pathways that may occur in Europa's crust. Calculations about the oxidation state of the hypothetical Europan ocean were estimated to support the sulfate-rich neutral liquid model as the origin of Europa's observed hydrated minerals and to facilitate their comparison with Tírez's hydrogeochemistry. Hydrogeochemical and mineralogical analyses showed that Tírez waters corresponded to Mg-Na-SO(4)-Cl brines with epsomite, hexahydrite, and halite as end members. A preliminary microbial ecology characterization identified two different microbial domains: a photosynthetically sustained community represented by planktonic/benthonic forms and microbial mat communities, and a subsurficial anaerobic realm in which chemolithotrophy predominates. Fluorescence in situ hybridization has been used to characterize the prokaryotic diversity of the system. The subsurficial community seemed to be dominated by sulfate-reducing bacteria and methanogens. Frozen Tírez brines were analyzed by Fourier-transform infrared techniques providing spectra similar to those reported previously using pure components and to the Galileo spectral data. Calorimetric measurements of Tírez brines showed pathways and phase metastability for magnesium sulfate and sodium chloride crystallization that may aid in understanding the processes involved in the formation of Europa's icy crust. The use of fluorescence hybridization techniques for microbial detection and characterization in hypersaline environments makes this methodology strongly advisable for future Europa astrobiological missions.

Chemical Phenomena↗
PubMed2005

The Alexander Project: the benefits from a decade of surveillance.

The Alexander Project, initiated in 1992 as an international, multicentre, longitudinal surveillance study of antimicrobial susceptibility among common respiratory pathogens, has been pivotal in defining the role of global surveillance. At the time, there were few studies in which data were collected in a way that allowed meaningful comparisons to be made between studies, locations or over time. The project instituted the use of a central laboratory and standardized methods for the collection of isolates and determination of susceptibility, and this was continued with the addition of two further reference laboratories. Data from the study have provided a resource for measuring trends in the susceptibility patterns of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis at country, regional and global levels. Determination and publication of quantitative MICs enabled detailed assessment of changes in susceptibility distributions and assessment of microbiological and potential clinical susceptibility using different breakpoints, including those based on pharmacokinetic/pharmacodynamic parameters. Comparisons of antimicrobial usage patterns and resistance prevalences over time allowed hypotheses to be examined with respect to the role of quantity and type of antimicrobial use in the selection and spread of resistance. The resulting collection of isolates has provided a valuable resource for molecular studies into the evolution of resistance over time and location; a substantial proportion of this collection is now in the public domain. This paper reviews the 10 years of the Alexander Project and the benefits it has brought to an understanding of the evolution of antibacterial resistance in community respiratory bacteria.

Anti-Bacterial Agents↗
PubMed2000

Evolution of chloramphenicol resistance, with emergence of cross-resistance to florfenicol, in bovine Salmonella Typhimurium strains implicates definitive phage type (DT) 104.

The prevalence of resistance to florfenicol, a phenicol drug newly introduced in veterinary therapy, was determined in 86 chloramphenicol-resistant Salmonella Typhimurium isolates from cattle collected during 1985-1995. All were highly resistant to chloramphenicol (MICs > or = 128 mg/L) and 38 were simultaneously resistant to florfenicol (MICs >16 mg/L) and to beta-lactam agents, spectinomycin, streptomycin, sulphonamides and tetracyclines. The isolates susceptible to florfenicol harboured the chloramphenicol acetyl transferase gene, cat of type I. All the florfenicol-resistant isolates harboured the floR resistance gene and the characteristic multiple resistance genetic locus, previously characterised in a S. Typhimurium DT104 strain and identified by a multiplex PCR. Plasmid profiles and ribotype patterns were determined for all the isolates. The florfenicol-resistant isolates were grouped into the same ribotyping pattern and presented similar plasmid profiles, whereas the florfenicol-susceptible isolates showed a wider genetic diversity that is usual for S. Typhimurium. Thus, the florfenicol-resistant isolates could represent a clonal cluster, closely related to, if not of DT104 phage type, which appeared in 1989 and is now predominant within chloramphenicol-resistant S. Typhimurium. The multiplex PCR provided a useful tool to survey further evolution of multiresistant S. Typhimurium strains.

Animals↗
PubMed2000

Evolution of lamivudine resistance in human immunodeficiency virus type 1-infected individuals: the relative roles of drift and selection.

Human immunodeficiency virus type 1 (HIV-1) rapidly develops resistance to lamivudine during monotherapy, typically resulting in the appearance at position 184 in reverse transcriptase (RT) of isoleucine instead of the wild-type methionine (M184I) early in therapy, which is later replaced by valine (M184V). M184V reduces viral susceptibility to drug in vitro by approximately 100-fold, but also results in a lower processivity of RT. We show that a drop in absolute viral fitness associated with the outgrowth of M184V results in a drop in viral load only in individuals with high CD4(+) counts, from whom we estimate the relative fitness of M184V in the presence of drug to be approximately 10% of that of the wild type prior to therapy. The timing of emergence of the M184V mutant varies widely between infected individuals. From analysis of the frequency of M184I and M184V mutants determined at multiple time points in seven individuals during lamivudine therapy, we estimated the fitness advantage of M184V over M184I during therapy to be approximately 23% on average. We have also estimated the average ratio of the frequencies of the two mutants prior to therapy to be 0. 2:1, with a range from 0.12:1 to 0.33:1. We have found that the differences between individuals in the rate of evolution of lamivudine resistance arise due to genetic drift affecting the relative frequency of M184I and M184V prior to therapy. These results show that stochastic effects can be significant in HIV evolution, even when there is large fitness difference between mutant and wild-type variants.

Anti-HIV Agents↗
PubMedDate not supplied

Parallel evolution of CCR5-null phenotypes in humans and in a natural host of simian immunodeficiency virus.

The C-C chemokine receptor CCR5 in humans and rhesus macaques (Macaca mulatta) serves as the primary coreceptor for cellular entry by macrophagetropic strains of human immunodeficiency virus type 1 (HIV-1) and all reported strains of simian immunodeficiency virus (SIV) [1-6]. Humans homozygous for a 32 bp deletion allele of CCR5, resulting in a null phenotype, are highly resistant to infection by HIV-1 [7-9], prompting development of therapies and vaccines targeting CCR5. We now report a novel deletion allele of CCR5, with an allele frequency of 0.04, in sooty mangabey monkeys (Cercocebus torquatus atys), a natural host of SIV (SIVsmm) [10]. The mutant protein was not expressed at the cell surface and accordingly did not function as a viral coreceptor. Primary activated lymphocytes from mangabeys heterozygous for the deletion allele expressed significantly less CCR5 on the cell surface. Moreover, SIV seroprevalence and viremia were comparable among CCR5 heterozygotes and wild-type animals. Parallel evolution of CCR5-null alleles in humans and sooty mangabeys suggests that similar negative selection pressures have acted against CCR5, as would occur during epidemics of infectious agents that require CCR5 for pathogenesis. Sooty mangabeys bred to homozygosity for the deletion allele will be useful for experimental studies on the context-dependent role of CCR5 in host defense and microbial pathogenesis.

Animals↗
PubMed1998

Granule-bound starch synthase: structure, function, and phylogenetic utility.

Interest in the use of low-copy nuclear genes for phylogenetic analyses of plants has grown rapidly, because highly repetitive genes such as those commonly used are limited in number. Furthermore, because low-copy genes are subject to different evolutionary processes than are plastid genes or highly repetitive nuclear markers, they provide a valuable source of independent phylogenetic evidence. The gene for granule-bound starch synthase (GBSSI or waxy) exists in a single copy in nearly all plants examined so far. Our study of GBSSI had three parts: (1) Amino acid sequences were compared across a broad taxonomic range, including grasses, four dicotyledons, and the microbial homologs of GBSSI. Inferred structural information was used to aid in the alignment of these very divergent sequences. The informed alignments highlight amino acids that are conserved across all sequences, and demonstrate that structural motifs can be highly conserved in spite of marked divergence in amino acid sequence. (2) Maximum-likelihood (ML) analyses were used to examine exon sequence evolution throughout grasses. Differences in probabilities among substitution types and marked among-site rate variation contributed to the observed pattern of variation. Of the parameters examined in our set of likelihood models, the inclusion of among-site rate variation following a gamma distribution caused the greatest improvement in likelihood score. (3) We performed cladistic parsimony analyses of GBSSI sequences throughout grasses, within tribes, and within genera to examine the phylogenetic utility of the gene. Introns provide useful information among very closely related species, but quickly become difficult to align among more divergent taxa. Exons are variable enough to provide extensive resolution within the family, but with low bootstrap support. The combined results of amino acid sequence comparisons, maximum-likelihood analyses, and phylogenetic studies underscore factors that might affect phylogenetic reconstruction. In this case, accommodation of the variable rate of evolution among sites might be the first step in maximizing the phylogenetic utility of GBSSI.

Amino Acid Sequence↗
PubMed2003

A rapid microtiter plate method to measure carbon dioxide evolved from carbon substrate amendments so as to determine the physiological profiles of soil microbial communities by using whole soil.

Sole-carbon-source tests (Biolog), designed to identify bacteria, have become very popular for metabolically fingerprinting soil microbial communities, despite disadvantages associated with the use of carbon source profiles that primarily select for fast-growing bacteria. In this paper we describe the use of an alternative method that combines the advantages of the Biolog community-level physiological profile (CLPP) method, in which microtiter-based detection plates are used, with the ability to measure carbon dioxide evolution from whole soil. This method facilitates measurement over short periods of time (4 to 6 h) and does not require the extraction and culturing of organisms. Deep-well microtiter plates are used as test wells into which soil is placed. The apparatus to fill the deep-well plates and interface it with a second removable detection plate is described. Two detection systems, a simple colorimetric reaction in absorbent alkali and scintillation counting with radioactive carbon sources, are described. The methods were compared to the Biolog-CLPP system by using soils under different vegetation types and soil treated with wastewater sludge. We aimed to test the hypothesis that using whole soil would have specific advantages over using extracts in that more immediate responses to substrates could be obtained that would reflect activity rather than growth. The whole-soil method was more rapid and gave earlier detection of C source use. Also, the metabolic fingerprints obtained could discriminate between sludge treatments.

Bacteria↗
PubMed2002

Cell-Surface display of heterologous proteins: From high-throughput screening to environmental applications.

A variety of expression systems for the display of either short peptides or fully folded proteins on E.coli and, to a lesser extent, on Gram-positive bacteria have been developed. The expression of proteins on the surface of microbial cells has proved extremely important for numerous applications ranging from combinatorial library screening and protein engineering, to whole cell biocatalysts and adsorbants for bioremediation purposes.

Bacterial Proteins↗
PubMed2005

Microbial starch-binding domain.

Glucosidic bonds from different non-soluble polysaccharides such as starch, cellulose and xylan are hydrolyzed by amylases, cellulases and xylanases, respectively. These enzymes are produced by microorganisms. They have a modular structure that is composed of a catalytic domain and at least one non-catalytic domain that is involved in polysaccharide binding. Starch-binding modules are present in microbial enzymes that are involved in starch metabolism; these are classified into several different families on the basis of their amino acid sequence similarities. Such binding domains promote attachment to the substrate and increase its concentration at the active site of the enzyme, which allows microorganisms to degrade non-soluble starch. Fold similarities are better conserved than sequences; nevertheless, it is possible to notice two evolutionary clusters of microbial starch-binding domains. These domains have enormous potential as tags for protein immobilization, as well as for the tailoring of enzymes that play a part in polysaccharide metabolism.

Bacteria↗
PubMed2002

The subsurface origin of microbial life on the Earth.

Life on Earth can be divided into life on the surface made possible by photosynthesis and subsurface life with chemical energy as the driving force. An understanding of both environments is central to our understanding of the origin of life, the search for novel microbial species in the subsurface and for extraterrestrial life or life signatures. In this manuscript, the surface and subsurface worlds are examined with a focus on the origin or assembly of bacterial life.

Bacteria↗
PubMed1998

Molecular analysis of diverse elements mediating VanA glycopeptide resistance in enterococci.

Differences were examined among 24 distinct elements mediating VanA-type glycopeptide resistance in enterococci isolated from hospital patients and non-human sources in the UK. The methods used included long-PCR restriction fragment length polymorphism (L-PCR RFLP) analysis and DNA hybridization. All elements had conserved vanRSHAX genes, but variation occurred upstream of vanR and downstream of vanX. Twenty-one VanA elements had significant alterations upstream of vanR in the transposition genes orf1 and orf2: either parts of these genes were absent or they were disrupted by IS1216V or IS3-like insertion sequences. Among VanA elements with alterations downstream of vanX, seven lacked vanY, one lacked both vanY and vanZ, and ten had copies of insertion sequence IS1216V between vanX and vanY. All VanA elements of group D (from geographically and temporally diverse enterococci) were characterized by the presence of an IS1216V/IS3-like/orf1 complex and a point mutation in vanX, both of which were absent from the other 23 groups of VanA elements. This finding is consistent with the dissemination of a stable resistance element. We conclude that L-PCR RFLP analysis, combined with DNA hybridization, merits further development for studying the evolution and epidemiology of VanA resistance elements in enterococci.

Animals↗
PubMed2006

Role of bacteriocin immunity proteins in the antimicrobial sensitivity of Streptococcus mutans.

Bacteria utilize quorum-sensing systems to modulate environmental stress responses. The quorum-sensing system of Streptococcus mutans is mediated by the competence-stimulating peptide (CSP), whose precursor is encoded by the comC gene. A comC mutant of strain GS5 exhibited enhanced antimicrobial sensitivity to a wide variety of different agents. Since the addition of exogenous CSP did not complement this phenotype, it was determined that the increased tetracycline, penicillin, and triclosan sensitivities resulted from repression of the putative bacteriocin immunity protein gene, bip, which is located immediately upstream from comC. We further demonstrated that the inactivation of bip or smbG, another bacteriocin immunity protein gene present within the smb operon in S. mutans GS5, affected sensitivity to a variety of antimicrobial agents. Furthermore, both the bip and smbG genes were upregulated in the presence of low concentrations of antibiotics and were induced during biofilm formation relative to in planktonic cells. These results suggest, for the first time, that the antimicrobial sensitivity of a bacterium can be modulated by some of the putative bacteriocin immunity proteins expressed by the organism. The implications of these observations for the evolution of bacteriocin immunity protein genes as well as for potential new chemotherapeutic strategies are discussed.

Anti-Bacterial Agents↗
PubMed1995

Adaptation of Xanthobacter autotrophicus GJ10 to bromoacetate due to activation and mobilization of the haloacetate dehalogenase gene by insertion element IS1247.

Monobromoacetate (MBA) is toxic for the 1,2-dichloroethane-degrading bacterium Xanthobacter autotrophicus GJ10 at concentrations higher than 5 mM. Mutants which are able to grow on higher concentrations of MBA were isolated and found to overexpress haloacid dehalogenase, which is encoded by the dhlB gene. In mutant GJ10M50, a DNA fragment (designated IS1247) had copied itself from a position on the chromosome that was not linked to the dhlB region to a site immediately upstream of dhlB, resulting in a 1,672-bp insertion. IS1247 was found to encode an open reading frame corresponding to 464 amino acids which showed similarity to putative transposases from two other insertion elements. In most of the other MBA-resistant mutants of GJ10, IS1247 was also present in one more copy than in the wild type, which had two copies located within 20 kb. After insertion to a site proximal to dhlB, IS1247 was able to transpose itself together with the dhlB gene to a plasmid, without the requirement of a second insertion element being present downstream of dhlB. The results show that IS1247 causes bromoacetate resistance by overexpression and mobilization of the haloacid dehalogenase gene, which mimics steps during the evolution of a catabolic transposon and plasmid during adaptation to a toxic growth substrate.

Acetates↗
PubMed2000

Nematode Parasitism Genes.

The ability of nematodes to live on plant hosts involves multiple parasitism genes. The most pronounced morphological adaptations of nematodes for plant parasitism include a hollow, protrusible stylet (feeding spear) connected to three enlarged esophageal gland cells that express products that are secreted into plant tissues through the stylet. Reverse genetic and expressed sequence tag (EST) approaches are being used to discover the parasitism genes expressed in nematode esophageal gland cells. Some genes cloned from root-knot (Meloidogyne spp.) and cyst (Heterodera and Globodera spp.) nematodes have homologues reported in genomic analyses of Caenorhabditis elegans and animal-parasitic nematodes. To date, however, the candidate parasitism genes endogenous to the esophageal glands of plant nematodes (such as the ß-1,4-endoglucanases) have their greatest similarity to microbial genes, prompting speculation that genes for plant parasitism by nematodes may have been acquired by horizontal gene transfer.

functional genomics↗
PubMed2005

Survival and growth of Yersinia enterocolitica strains inoculated in skimmed milk treated with high hydrostatic pressure.

Four human pathogenic strains of Yersinia enterocolitica (serotypes O:1, O:3, O:8, and O:9) were inoculated (7-8 log CFU/ml) in UHT skimmed milk and treated at 300, 400, and 500 MPa for 10 min at 20 degrees C, and then kept at 8 degrees C to assess their evolution for 15 days. Treatments at 400 and 500 MPa caused the highest lethality, generally reaching counts below detection level (1 CFU/ml) in the culture media. At 300 MPa, the most baroresistant serotypes were O:3 and O:8. After 15 days of storage at 8 degrees C, Y. enterocolitica showed growth over 8 log (CFU/ml) in all treatments. Kinetic study of microbial inactivation in skimmed milk was performed with serotype O:8 at 300 MPa, showing a tailing after 35 min of pressure treatment.

Animals↗
PubMed2002

Insect inhibitors of metalloproteinases.

Two types of peptidic metalloproteinase inhibitors have recently been identified in insects. A homologue of vertebrate tissue inhibitors of metalloproteinases (TIMPs) was found in the fruitfly Drosophila melanogaster which may contributes to regulation of a corresponding matrix metalloproteinase (MMP). The first member of MMPs from insects which shares similarity with vertebrate MMPs has also been cloned and characterized from Drosophila, suggesting conserved evolution of both MMPs and TIMPs. The first insect inhibitor of metalloproteinases (IMPI), which was identified in larvae of the greater wax moth, Galleria mellonella, shares no sequence similarity with known vertebrate or invertebrate proteins and represents the first non-TIMP-like inhibitor of metalloproteinases reported to date. In contrast to TIMPs, the IMPI is not active against MMPs but inhibits microbial metalloproteinases such as bacterial thermolysin. Insects may recognize such toxic metalloproteinases associated with invading pathogens by particular peptidic fragments that result from their nonregulated activity within the hemolymph. Metalloproteinases induce expression of the IMPI along with other antimicrobial proteins in course of humoral immune response of G. mellonella, thereby mediating regulation of metalloproteinase activity released within the hemolymph and inhibition of pathogen development as well.

Animals↗
PubMed1995

The immune self: a selectionist theory of recognition, learning, and remembering within the immune system.

In this paper, I have briefly explored metaphors shared by the immune and nervous systems and shown that this exercise can lead to the elucidation of common principles of organization, as well as to predictions concerning how the immune system functions. Metaphor itself undoubtedly reflects the way in which we categorize and retrieve information 44], so it is not surprising that the deep processes of language tend to sample information from related data categories. Although the nervous and immune systems are obviously not the same and metaphors are indeed just that, my primary goal has been to suggest that by virtue of their having evolved in parallel over millions of years, the nervous and immune systems currently use the same archetypal principles and strategies to address related challenges in information processing and retrieval. Ultimately, nature is conservative. One need only look at a tree, a river, the airways, or the vascular bed in order to see how a fractal pattern of repetitive dichotomous branching has been used by each, in order to optimize the transport of fluids over large distances [45]. While each system has had to adopt different materials in order to solve the problem, the shape of their solutions is remarkably alike. In the immune and nervous systems, the elements used to produce optimal functional responses are also quite different, but again the solutions have been achieved by comparable strategies. I am certain that these two great systems of information processing, each responding with vastly different kinetics, will prove to be far more integrally interdependent than has been previously recognized. For example, should a swift response by the immune system be required in an overwhelming invasion by microbial pathogens, the immune system may be able to cooperate with the rapidly reacting nervous system to rid the host of the invaders. In this regard, we have shown that the beta-adrenergic hormone epinephrine rapidly increases the traffic of memory T-cells to mucosal sites, presumably representing an immune component of the fight-or-flight response [46]. Neural evolution appears to have as its goal the development of more efficient information processing systems that lead to higher levels of consciousness. However, in modern times, technologic advances in information processing have rapidly outstripped the slower adaptations that can be made by evolution. In order to satisfy his compulsive quest for information, man has recently developed and recruited the aid of computers.(ABSTRACT TRUNCATED AT 400 WORDS)

Association Learning↗