Search

Author(s): Lale Guliyeva [sup.1] , Yilmaz Tabel [sup.2] , Ali Düzova [sup.3] , Nusret Akpolat [sup.4] , Seza Özen [sup.5] , Rezan Topaloglu [sup.3] , Betül Sözeri [sup.6] Author Affiliations: [...]

The side effects associated with tuberculosis therapy bring with them the risk of noncompliance and subsequent drug resistance. Increasing the therapeutic index of antituberculosis drugs should thus improve treatment effectiveness. Several antituberculosis compounds require in situ metabolic activation to become inhibitory. Various thiocarbamide-containing drugs, including ethionamide, are activated by the mycobacterial monooxygenase EthA, the production of which is controlled by the transcriptional repressor EthR. Here we identify drug-like inhibitors of EthR that boost the bioactivation of ethionamide. Compounds designed and screened for their capacity to inhibit EthR-DNA interaction were co-crystallized with EthR. We exploited the three-dimensional structures of the complexes for the synthesis of improved analogs that boosted the ethionamide potency in culture more than tenfold. In Mycobacterium tuberculosis-infected mice, one of these analogs, BDM31343, enabled a substantially reduced dose of ethionamide to lessen the mycobacterial load as efficiently as the conventional higher-dose treatment. This provides proof of concept that inhibiting EthR improves the therapeutic index of thiocarbamide derivatives, which should prompt reconsideration of their use as first-line drugs., The directly observed treatment short course, a multidrug therapy program developed by the World Health Organization, is one of the most efficient weapons against the global tuberculosis epidemic. Nevertheless, the [...]

Resistant TB Is a Serious Threat to Global Health Tuberculosis (TB) remains the leading cause of death from a largely preventable and curable infectious disease, with an estimated 1.7 million [...]

Resistance to many antimalaria drugs developed on the Cambodia-Thailand border long before developing elsewhere. Because antimalaria resistance is now a global problem, artemisinin-based combination therapies (ACTs) are the first-line therapies [...]

Lung cancers caused by activating mutations in the epidermal growth factor receptor (EGFR) are initially responsive to small molecule tyrosine kinase inhibitors (TKIs), but the efficacy of these agents is often limited because of the emergence of drug resistance conferred by a second mutation, T790M. Threonine 790 is the 'gatekeeper' residue, an important determinant of inhibitor specificity in the ATP binding pocket. The T790M mutation has been thought to cause resistance by sterically blocking binding of TKIs such as gefitinib and erlotinib, but this explanation is difficult to reconcile with the fact that it remains sensitive to structurally similar irreversible inhibitors. Here, we show by using a direct binding assay that T790M mutants retain low-nanomolar affinity for gefitinib. Furthermore, we show that the T790M mutation activates WT EGFR and that introduction of the T790M mutation increases the ATP affinity of the oncogenic L858R mutant by more than an order of magnitude. The increased ATP affinity is the primary mechanism by which the T790M mutation confers drug resistance. Crystallographic analysis of the T790M mutant shows how it can adapt to accommodate tight binding of diverse inhibitors, including the irreversible inhibitor HKI-272, and also suggests a structural mechanism for catalytic activation. We conclude that the T790M mutation is a 'generic' resistance mutation that will reduce the potency of any ATP-competitive kinase inhibitor and that irreversible inhibitors overcome this resistance simply through covalent binding, not as a result of an alternative binding mode. lung cancer | tyrosine kinase | x-ray crystallography

Objective In the Republic of Korea (ROK), soldiers stationed where there is a risk of contracting malaria have received antimalarial chemoprophylaxis since 1997. However, chemoprophylaxis may facilitate the development of drug resistance, and late primary attacks in individuals who have received chemoprophylaxis are becoming more frequent. We investigated the association between chemoprophylaxis and the epidemiological characteristics and effectiveness of treatment for re-emergent Plasmodium vivax malaria, using a nationwide malaria database. Methods Among soldiers at risk of malaria between 1999 and 2001, we reviewed all P. vivax malaria cases (1158) that occurred before 31 December 2003. Early and late primary attacks were defined as cases occurring [less than or equal to] 2 or > 2 months after the last day of exposure to risk of malaria, respectively. Findings Of these cases, 634 (72.0%) had received chemoprophylaxis, and 324 (28.0%) had not. Cases occurred mostly in summer, with a peak in July-August. Stratification by chemoprophylaxis history revealed different rimes to onset. Early primary attacks were more prevalent in the group not receiving chemoprophylaxis, while in the group receiving chemoprophylaxis most cases were late primary attacks. Of the latter, 312 out of 461 (67.7%) did not take primaquine regularly. After treatment of the first attack, 14 (1.2%) of 1158 were re-treated; all re-treated cases were cured using the same doses and regimen used for the first treatment. Conclusion In ROK, the increase in late primary episodes of re-emergent P. vivax malaria is associated with the use of antimalarial chemoprophylaxis., Voir page 833 le resume en francais. En la pagina 833 figura un resumen en espanol. Introduction Plasmodium vivax, the causative agent of vivax malaria, has been endemic in the [...]

We surveyed the populations of 19 European countries to compare the prevalence of antimicrobial drug self-medication in the previous 12 months and intended self-medication and storage and to identify the [...]

Ever since the 1930s large number of antibiotics or potent anti-microbial agents, have been developed. With the introduction of new products, a new issue, termed, drug resistance has come to the focus. The causes of drug resistance, such as changes in the genetic activity of microbial pathogens, or altering of the binding site by bacteria, or excessive use of drugs; the consequences of drug resistance, and the necessary steps, healthcare professionals need to take, are detailed.

A hypothesis to test whether blips represent random biological and statistical variation around mean steady-state HIV-1 RNA levels slightly below 50 copies/mL rather than biologically significant elevations in viremia is presented. It is concluded that most blips appear to represent random biological and statistical variation around mean HIV-1 levels below 50 copies/mL rather than clinically significant elevations in viremia.

Byline: Elisabeth Meyer (1), Frank Schwab (2,4), Daniel Jonas (1), Henning Rueden (2,4), Petra Gastmeier (3,4), Franz D. Daschner (1,4) Keywords: Antimicrobial use; Intensive care unit; SARI; Surveillance Abstract: Objective To study antimicrobial use for benchmarking and ensuring quality of antimicrobial treatment and to identify risk factors associated with the high use of antimicrobials in German intensive care units (ICUs) through implementation of the SARI (Surveillance of Antimicrobial Use and Antimicrobial Resistance in ICUs) system. Design Prospective, unit-based surveillance on antimicrobial use from February, 2000, until June, 2002. The data are standardised by use of the defined daily dose (DDD) for each antimicrobial defined by the WHO and by calculating use per 1000 patient days. Setting The data were obtained from 35 German ICUs and stratified by type of ICU (medical, surgical, interdisciplinary). Results To date, the project covers a total of 266,013 patient days in 744 reported ICU months and 354,356 DDDs. Mean antimicrobial use density (AD) was 1,332 DDD/1000 patient days and was correlated with length of stay. Penicillins with beta-lactamase inhibitor (AD 338.3) and quinolones (155.5) were the antimicrobial group with the highest ADs. Comparison with US ICARE (Intensive Care Antimicrobial Resistance Epidemiology)/AUR (Antimicrobial Use and Resistance) data revealed a higher AD for glycopeptides and 3rd generation cephalosporins in ICARE/AUR ICUs, but a higher AD for carbapenems in German SARI ICUs regardless of the type of ICU. In the multivariate analysis, length of stay was an independent risk factor for an AD above the 75% percentile of the total amount of antimicrobials used (OR 1.96 per day) likewise, for the AD above the 75% percentile of carbapenems (OR 1.90 per day) and penicillins with extended spectrum (OR 2.01 per day). High use of glycopeptides and quinolones (AD >75% percentile) correlated with central venous catheter (CVC) rate (OR 1.14 per CVC day per 100 patient days and 1.16, respectively). Conclusion The SARI data on antimicrobials serve ICUs as a benchmark by which to improve the quality of antimicrobial drug administration and for international comparison. Author Affiliation: (1) Institute of Environmental Medicine and Hospital Epidemiology, Freiburg University Hospital, Hugstetter Strasse 55, 79106, Freiburg, Germany (2) Institute of Hygiene and Environmental Medicine, University Hospital Benjamin Franklin and Department of Hospital Epidemiology, University Hospital Charite , Free University Berlin and Humboldt University Berlin, Hindenburgdamm 27, 12203, Berlin, Germany (3) Institute of Medical Microbiology and Hospital Epidemiology, Hannover School of Medicine, Carl Neuberg Strasse 1, 30625, Hannover, Germany (4) National Reference Centre for Surveillance of Nosocomial Infections, Heubnerweg 8, 14059, Berlin, Germany Article History: Registration Date: 01/03/2004 Received Date: 26/05/2003 Accepted Date: 26/02/2004 Online Date: 26/03/2004 Article note: Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00134-004-2266-9

In response to low iron availability, Vibrio parahaemolyticus synthesizes and secretes a polyhydroxycarboxylate-type siderophore vibrioferrin which is composed of 1 mol each of 2-ketoglutaric acid, L-alanine, ethanolamine, and citric acid. We have previously reported the cloning and characterization of the pvuA gene, which encodes the 78-kDa outer membrane receptor protein for ferric vibrioferrin. In this study, nine genes involved in the biosynthesis and transport of vibrioferrin have been identified in the genomic regions surrounding the pvuA gene. The genes were sequenced, and gene disruptants were constructed by insertion mutation for phenotype analysis. Five of the genes, named pvsABCDE, constitute an operon that is expressed under iron-limiting conditions. Homology searches of their predicted protein products suggested that the four genes pvsABDE are implicated in the biosynthesis of the siderophore. Another gene in the same operon, pvsC, encodes a putative exporter that is homologous to members of the major facilitator superfamily of multidrug efflux pumps. The remaining four genes, named pvuBCDE, encode proteins strongly homologous to Escherichia coli FecBCDE, respectively, which are components of the ATP-binding cassette transporter system for ferric dicitrate. Reverse transcriptase PCR analysis revealed that these transport genes are transcribed as a single mRNA with the upstream genes, psuA and pvuA. Phenotypic comparison between the wild-type strain and its targeted gene disruptants supported the biological functions for the respective operons that were expected on the basis of the homology search.

Yersinia enterocolitica 29930 (biotype 1A; O: 7,8), the producing strain of the phage-tail-like bacteriocin enterocoliticin, possesses a plasmid-encoded conjugative type IV transfer system. The genes of the conjugative system were found by screening of a cosmid library constructed from total DNA of strain 29930. The cosmid Cos100 consists of the vector SuperCos1 and an insert DNA of 40 303 bp derived from a cryptic plasmid of strain 29930. The conjugative transfer system consists of genes encoding a DNA transfer and replication system (Dtr) with close relationship to the mob region of the mobilizable plasmid CloDF13 and a gene cluster encoding a mating pair formation system (Mpf) closely related to the Mpf system of the IncX plasmid R6K. However, a gene encoding a homologue of TaxB, the coupling protein of the IncX system, is missing. The whole transfer region has a size of approximately 17 kb. The recombinant plasmid Cos100 was shown to be transferable between Escherichia coil and Yersinia with transfer frequencies up to 0.1 transconjugants per donor. Mutations generated by inserting a tetracycline cassette into putative tri genes yielded a transfer-deficient phenotype. Conjugative transfer of the cryptic plasmid could not be demonstrated in the original host Y. enterocolitica 29930. However, a kanamycin-resistance-conferring derivative of the plasmid was successfully introduced into E. coil K-12 by transformation and was shown to be self-transmissible. Furthermore, Southern blot hybridization and PCR experiments were carried out to elucidate the distribution of the conjugative transfer system in Yersinia. In total, six Y. enterocolifica biotype 1A strains harbouring closely related systems on endogenous plasmids were identified.

A constitutively active mutant of histidine kinase sensor EvgS was found to confer multi-drug resistance (MDR) to an acrA-deficient Escherichia coil, indicating the relationship between the two-component system EvgAS and the expression of the MDR system. The observed MDR also depended on an outer-membrane channel, TolC. Microarray and S1 mapping assays indicated that, in the presence of this constitutive mutant ErgS, the level of transcription increased for some MDR genes, including the drug efflux genes emrKY, yhiUV, acrAB, mdfA and tolC. Transcription in vitro of emrK increased by the addition of phosphorylated EvgA. Transcription activation of tolC by the activated EvgS was, however, dependent on both EvgAS and PhoPQ ([Mg.sup.2+]-responsive two-component system), in agreement with the presence of the binding site (PhoP box) for the regulator PhoP in the tolC promoter region. Transcription in vitro of yhiUV also appears to require an as-yet-unidentified additional transcriptional factor besides EvgA. Taken together we propose that the expression of the MDR system is under a complex regulatory network, including the phosphorylated EvgA serving as the master regulator.

Research has been conducted on adherence to antiretroviral therapy associated with AIDS progression, viral load suppression and death in HIV-infected persons. The use of computer-assisted self-interviewing technology in identifying errors in HIV antiretroviral regimen and in monitoring adherence in order to maximize antiretroviral therapy benefits is discussed.

Research has been conducted on MRP1 membrane glycoprotein which is responsible for multidrug resistance to tumor cells. The role of glutathione in MRP1 drug transport has been investigated via the synthesis of agosterol A photoaffinity analogue, and the details are reported.

During 1995 to 1999, we collected 1,210 Salmonella isolates; 629 were from Finnish travelers returning from abroad. These isolates were tested for susceptibility by determining MICs to ciprofloxacin, nalidixic acid, [...]

HIV reverse transcriptase (RT) is one of the main targets for the action of anti-AIDS drugs. Many of these drugs [e.g., 3[prime].azido-3[prime]-deoxythymidine (AZT) and 2[prime],3[prime]dideoxyinosine (ddI)] are analogues of the nucleoside substrates used by the HIV RT. One of the main problems in anti-HIV therapy is the selection of a mutant virus with reduced drug sensitivity. Drug resistance in HIV is generated for nucleoside analogue inhibitors by mutations in HIV RT. However, most of these mutations are situated some distance from the polymerase active site, giving rise to questions concerning the mechanism of resistance. To understand the possible structural bases for this, the crystal structures of AZT- and ddI-resistant RTs have been determined. For the ddI. resistant RT with a mutation at residue 74, no significant conformational changes were observed for the p66 subunit. In contrast, for the AZT-resistant RT (RTMC) bearing four mutations, two of these (at 215 and 219) give rise to a conformational change that propagates to the active site aspartate residues. Thus, these drug resistance mutations produce an effect at the RT polymerase site mediated simply by the protein. It is likely that such long-range effects could represent a common mechanism for generating drug resistance in other systems.

Researchers are developing new drugs to treat diseases that no longer respond to methotrexate. Methotrexate is used to treat many types of cancer as well as rheumatoid arthritis, psoriasis and autoimmune diseases. It inhibits the enzyme dihydrofolate reductase, which ultimately inhibits DNA replication and causes cell death. However, the cells can become resistant to methotrexate by producing more of the enzyme or changing the transport and metabolism of methotrexate. Mutations in the gene for the enzyme have also been found in drug-resistant tumors. Methotrexate resistance can also occur if the retinoblastoma protein is defective.

The open reading frame encoding human bleomycin hydrolase (hBH) consists of 1365 bases and produces a protein with 455 amino acids. The protein is 40% and 89.5% identical to the yeast and rabbit bleomycin hydrolase, respectively. The protein functions as a protease and efficiently degrades bleomycin A2 and B2. Most human organs have low levels of hBH while tumor cell lines have high hBH levels. The high hBH levels are probably responsible for the resistance of tumor cells to bleomycin. The gene produces a 52 kDa protein in Spodoptera frugiperda Sf6 cells that behaves as an aminopeptidase.

Direct observation of the administration of tuberculosis therapy may reduce the incidence of primary drug resistance, acquired drug resistance and relapse. Drug therapy for tuberculosis is usually effective, but only if patients follow the regimen their doctors prescribe. Failure to comply leads to a recurrence of tuberculosis in many patients, often in a more resistant and harder to treat form. A total of 581 patients with tuberculosis were directly observed by health workers each time they took their medicine. This group's recovery rate was then compared to that of a group of 407 patients who were not observed. There was primary drug resistance in 6.7% of the observed group, compared to 13% of the non-observed patients. Acquired resistance was 2.1% in the observed group and 14% in the non-observed group. The overall relapse rate for the non-observed group was 20.9%, but only 5.5% in the observed group.

Research has been conducted on tetracycline-resistant gram-negative fish farm bacteria. The authors have isolated these bacteria, and have determined the DNA sequence of the bacteria's genes.