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Resistance Development (resistance + development)
Selected AbstractsStatus of Streptomycin Resistance Development in Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola in China and their Resistance CharactersJOURNAL OF PHYTOPATHOLOGY, Issue 9 2010Ying Xu Abstract Rice leaves with bacterial blight or bacterial leaf streak symptoms were collected in southern China in 2007 and 2008. Five hundred and thirty-four single-colony isolates of Xanthomonas oryzae pv. oryzae and 827 single-colony isolates of Xanthomonas oryzae pv. oryzicola were obtained and tested on plates for sensitivity to streptomycin. Four strains (0.75%) of X. oryzae pv. oryzae isolated from the same county of Province Yunnan were resistant to streptomycin, and the resistance factor (the ratio of the mean median effective concentration inhibiting growth of resistant isolates to that of sensitive isolates) was approximately 226. The resistant isolate also showed streptomycin resistance in vivo. In addition to resistant isolates, isolates of less sensitivity were also present in the population of X. oryzae pv. oryzae from Province Yunnan. However, no isolates with decreased streptomycin-sensitivity were obtained from the population of X. oryzae pv. oryzicola. Mutations in the rpsL (encoding S12 protein) and rrs genes (encoding 16S rRNA) and the presence of the strA gene accounting for streptomycin resistance in other phytopathogens or animal and human pathogenic bacteria were examined on sensitive and resistant strains of X. oryzae pv. oryzae by polymerase chain reaction amplification and sequencing. Neither the presence of the strA gene nor mutations in the rpsL or rrs were found, suggesting that different resistance mechanisms are involved in the resistant isolates of X. oryzae pv. oryzae. [source] Problems of resistance development in arthropod pests of agricultural crops in RussiaEPPO BULLETIN, Issue 1 2008G. I. Sukhoruchenko This paper presents the results of long-term monitoring of insecticide resistance in populations of agricultural pests in Russia. Over the last 45 years, resistance developments were recorded for 36 arthropod pest species in 11 agricultural crops and pastures in relation to nearly all commonly used plant protection products. Development of group, cross and multiple resistance has been revealed in populations of many economically important pests. Toxicological and phenotypical (for Colorado potato beetle) methods have been devised to monitor the development of pesticide resistance. Based on experience over the last century, systems aimed at preventing the development of pest resistance to insecticides and acaricides are elaborated. These systems are based on resistance monitoring and using plant protection measures which minimize the toxic pressure on agroecosystems. [source] Isolation of transcripts from Diabrotica virgifera virgifera LeConte responsive to the Bacillus thuringiensis toxin Cry3Bb1INSECT MOLECULAR BIOLOGY, Issue 3 2010A. Sayed Abstract Crystal (Cry) proteins derived from Bacillus thuringiensis (Bt) have been widely used as a method of insect pest management for several decades. In recent years, a transgenic corn expressing the Cry3Bb1 toxin has been successfully used for protection against corn rootworm larvae (genus Diabrotica). The biological action of the Bt toxin in corn rootworms has not yet been clearly defined. Because development of resistance to Bt by corn rootworms will have huge economic and ecological costs, insight into larval response to Bt toxin is highly desirable. We identified 19 unique transcripts that are differentially expressed in D. virgifera virgifera larvae reared on corn transgenic for Cry3Bb1. Putative identities of these genes were consistent with impacts on metabolism and development. Analysis of highly modulated transcripts resulted in the characterization of genes coding for a member of a cysteine-rich secretory protein family and a glutamine-rich membrane protein. A third gene that was isolated encodes a nondescript 132 amino acid protein while a fourth highly modulated transcript could not be further characterized. Expression patterns of these four genes were strikingly different between susceptible and resistant western corn rootworm populations. These genes may provide useful targets for monitoring of Bt exposure patterns and resistance development in pest and non-target insect populations. [source] Differential mRNA expression levels and gene sequences of carboxylesterase in both deltamethrin resistant and susceptible strains of the cotton aphid, Aphis gossypiiINSECT SCIENCE, Issue 3 2008Chuan-Wang Cao Abstract Extensive use of insecticides on cotton has prompted resistance development in the cotton aphid, Aphis gossypii (Glover) in China. A deltamethrin-selected population of cotton aphids from Xinjiang Uygur Autonomous Region, China with 228.59-fold higher resistance to deltamethrin was used to examine how carboxylesterase conferred resistance to this pyrethroid insecticide. The carboxylesterase activity in the deltamethrin-resistant strain was 3.67-, 2.02- and 1.16-fold of the susceptible strain when using ,-naphthyl acetate (,-NA), ,-naphthyl acetate (,-NA) and ,-naphthyl butyrate (,-NB) as substrates, respectively. Carboxylesterase cDNA was cloned and sequenced from both deltamethrin-resistant and susceptible strains. The cDNA contained 1581 bp open reading frames (ORFs) coding a 526 amino acid protein. Only one amino acid substitution (Val87 -Ala) was observed between deltamethrin-resistant and susceptible strains but it is not genetically linked to resistance by the catalytic triad and signature motif analysis. The real-time polymerase chain reaction analysis indicated that the resistant strain had a 6.61-fold higher level of carboxylesterase mRNA than the susceptible strain. The results revealed that up-regulation of the carboxylesterase gene, not modified gene structure, may be responsible for the development of resistance in cotton aphids to deltamethrin. [source] Assessment of resistance to colicinogenic Escherichia coli by E. coli O157:H7 strainsJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2005G. P. Schamberger Abstract Aims:, To assess a collection of 96 Escherichia coli O157:H7 strains for their resistance potential against a set of colicinogenic E. coli developed as a probiotic for use in cattle. Methods and Results:,Escherichia coli O157:H7 strains were screened for colicin production, types of colicins produced, presence of colicin resistance and potential for resistance development. Thirteen of 14 previously characterized colicinogenic E. coli strains were able to inhibit 74 serotype O157:H7 strains. Thirteen E. coli O157:H7 strains were found to be colicinogenic and 11 had colicin D genes. PCR products for colicins B, E-type, Ia/Ib and M were also detected. During in vitro experiments, the ability to develop colicin resistance against single-colicin producing E. coli strains was observed, but rarely against multiple-colicinogenic strains. The ability of serotype O157:H7 strains to acquire colicin plasmids or resistance was not observed during a cattle experiment. Conclusions:,Escherichia coli O157:H7 has the potential to develop single-colicin resistance, but simultaneous resistance against multiple colicins appears to be unlikely. Colicin D is the predominant colicin produced by colicinogenic E. coli O157:H7 strains. Significance and Impact of the Study:, The potential for resistance development against colicin-based strategies for E. coli O157:H7 control may be very limited if more than one colicin type is used. [source] Management of patients with decompensated hepatitis B virus associated cirrhosisLIVER TRANSPLANTATION, Issue S2 2008Fabien Zoulim Key Points 1Hepatitis B virus replication is associated with a severe outcome in patients with decompensated cirrhosis. 2Viral suppression induced by antivirals results in a clinical improvement that allows liver transplantation to be delayed or avoided. 3Early treatment intervention is mandatory in patients with decompensated cirrhosis because of the delay in the restoration of liver functions. 4Lamivudine is no longer the drug of choice because the initial enthusiasm has been tempered by the high rate of resistance development. 5Early add-on therapy with adefovir allows us to rescue lamivudine resistance, but its use may be limited by nephrotoxicity. 6Studies are ongoing with the newer generation of antivirals (telbivudine, tenofovir, entecavir, and emtricitabine) in monotherapy or in combination to determine the best strategy for achieving rapid and prolonged suppression of viral replication. These improved strategies should enhance treatment success enough to obtain clinical stabilization, to delay or prevent the need for transplantation, and to reduce the risk of hepatitis B virus recurrence on the graft. Liver Transpl 14:S1,S7, 2008. © 2008 AASLD. [source] Investigation of risk factors for tonsillopharyngitis with macrolide resistant Streptococcus pyogenes in Turkish childrenPEDIATRICS INTERNATIONAL, Issue 6 2002Abstract Background: Streptococcus pyogenes is the most important causative agent of tonsillopharyngitis. Although penicillin is the drug of choice in streptococcal tonsillopharyngitis, macrolides are recommended drugs in patients who have an allergy to penicillin. However, resistance to macrolides is an important problem in some regions of the world. Risk factors for resistance development have not been investigated sufficiently. Objectives: To investigate the risk factors for the development of tonsillopharyngitis with macrolide resistant S. pyogenes. Methods: Three hundred and forty-five children with tonsillopharyngitis caused by S. pyogenes were investigated for various risk factors. Streptococcus pyogenes isolated from children's throat culture were examined for erythromycin, clarithromycin and azithromycin susceptibility. Results: Two hundred and sixty-three children were found eligible for the analysis of risk factors. Resistances to erythromycin, clarithromycin and azithromycin were detected as 3.8, 4.2 and 4.2%, respectively. Macrolide use of the family members in the last 3 months (odds ratio = 7.04, P = 0.005) has been determined to be a risk factor for the development of tonsillopharyngitis with macrolide resistant S. pyogenes. Conclusion: Restriction of macrolide antibiotic use appears to be the most important measure to prevent the development of tonsillopharyngitis with resistant S. pyogenes. [source] Evaluation of the toxicity of 17 essential oils against Choristoneura rosaceana (Lepidoptera: Tortricidae) and Trichoplusia ni (Lepidoptera: Noctuidae),PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 10 2010Cristina M Machial Abstract BACKGROUND: The obliquebanded leafroller, Choristoneura rosaceana Harris, and the cabbage looper, Trichoplusia ni Hübner, are serious fruit and vegetable pests requiring multiple insecticide applications per year. To reduce non-target exposure to hazardous insecticides and to curb resistance development, alternative controls are required. Accordingly, a selection of 17 essential oils was screened against both lepidopteran pests, and the influence of azinphos-methyl resistance on essential oil toxicity to C. rosaceana was studied. RESULTS: Of the 17 essential oils screened, patchouli oil (Pogostemon cablin Benth.) and thyme oil (Thymus vulgaris L.) were selected for further testing against C. rosaceana, whereas patchouli oil, garlic oil (Allium sativum L.) and lemongrass oil (Cymopogon nardus L.) were selected for further testing against T. ni. LC50 and LD50 values confirmed that patchouli oil was the most toxic to C. rosaceana larvae, with LC50 = 2.8 µL mL,1 and LD50 = 8.0 µg insect,1. Garlic oil was the most toxic oil to T. ni larvae with LC50 = 3.3 µL mL,1 and LD50 = 22.7 µg insect,1, followed by patchouli oil and lemongrass oil. Azinphos-methyl-resistant leafrollers were 1.5-fold more tolerant to patchouli oil and 2.0-fold more tolerant to thyme oil. CONCLUSIONS: Based on these results, patchouli oil and other essential oils have sufficient efficacy to be considered as components of an essential oil-based insecticide that targets these lepidopteran pests. Copyright © 2010 Crown in the right of Canada. Published by John Wiley & Sons, Ltd [source] Biochemical mechanisms of methoxyfenozide resistance in the cotton leafworm Spodoptera littoralisPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 7 2009Hadi Mosallanejad Abstract BACKGROUND: Methoxyfenozide is a lepidopteran-specific insecticide that belongs to a new group of insecticides, the non-steroidal ecdysteroid agonists, also called moulting accelerating compounds (MACs). To investigate the risk of resistance and possible mechanisms conferring resistance to methoxyfenozide, the authors selected in the laboratory for a resistant strain of the cotton leafworm Spodoptera littoralis (Boisd.), which is a representative lepidopteran model and an important pest in cotton and vegetables worldwide, with a high risk for resistance development. RESULTS: After selection with methoxyfenozide during 13 generations, toxicity data showed that the selected strain developed fivefold resistance to methoxyfenozide in comparison with the susceptible strain. Measurement of the detoxification enzymes demonstrated that the monooxygenase (MO) activity was 2.1 times higher in the selected strain, whereas there was no change for esterases and glutathione- S -transferases. When the inhibitors piperonyl butoxide (PBO), S,S,S -tributyl phosphorotrithioate (DEF) and diethyl maleate were tested as synergists, the respective synergistic ratios were 0.97, 0.96 and 1.0 for the susceptible strain, and 2.2, 0.96 and 1.1 for the resistant strain. The significant synergistic effect by PBO concurs with the increased MO activity in the selected strain. CONCLUSION: Taken overall, the present study supports the importance of MO-mediated metabolism in resistance to methoxyfenozide, directing tactics to fight against resistance development for this novel group of insecticides. Copyright © 2009 Society of Chemical Industry [source] Comparison of dose responses and resistance ratios in four populations of the rice stem borer, Chilo suppressalis (Lepidoptera: Pyralidae), to 20 insecticidesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2008Yue Ping He Abstract BACKGROUND: Chemical control is a major strategy for suppressing the rice stem borer, Chilo suppressalis (Walker). Owing to their high toxicity and increasing resistance development in the target insect, many insecticides will be phased out entirely in 2007 in China. Alternatives with relatively low toxicity are urgently needed to replace traditional chemicals for rice stem borer control. In this study, the authors examined four field populations of C. suppressalis for their toxicological responses to more than 20 insecticides, including a few low-toxicity organophosphates and many novel pesticides. Interpopulation resistance levels to 12 conventional insecticides were also compared. RESULTS: Based on LD50 values, the rice stem borer was most sensitive to avermectins and fipronil (LD50 < 1 ng larva,1). The stem borers exhibited the least sensitivity to endosulfan (LD50 > 100 ng larva,1) and monosultap (LD50 > 1000 ng larva,1). Insect growth regulators and chitin synthase inhibitors showed great efficacy against C. suppressalis, especially against populations that had developed resistance to conventional insecticides. Four field populations showed variable tolerance levels to many insecticides. LYG05 was the most susceptible population, only with a low level of resistance to monosultap (RR = 6.6). NC05 and GL05 populations exhibited intermediate tolerance levels with RR values up to 20.4 and 52.8 respectively. RA05 was the most resistant population to many insecticides, with resistance ratios up to 76.2. CONCLUSION: The results from this study provide valuable information for selection and adoption of new alternative insecticides and for resistance management of the rice stem borer. Copyright © 2008 Society of Chemical Industry [source] Insecticide susceptibility of surviving Cotesia plutellae (Hym: Braconidae) and Diaeretiella rapae (M'Intosh) (Hym: Aphidiidae) as affected by sublethal insecticide dosages on host insectsPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 9 2007Yong Wen Lin Abstract The effects of sublethal dosages of insecticides applied to Plutella xylostella L. (Lepidoptera: Yponomeutidae) and Lipaphis erysimi Kaltenbach (Homoptera: Aphidiidae) on the insecticide susceptibility of the surviving endoparasitoids, Cotesia plutellae Kurdjumov (Hymenoptera: Braconidae) and Diaeretiella rapae (M'Intosh) (Hymenoptera: Aphidiidae), were studied in Shangjie, Minhou, China. The susceptibility to methamidophos and the sensitivity of acetylcholinesterase (AChE) to methamidophos and dichlorvos in the adults of host insects were substantially lower than those in the two parasitoids. The host insects were treated with sublethal dosages of methamidophos in P. xylostella and of methamidophos and avermectin in L. erysimi. The cocoon formation in the two parasitoids decreased significantly, from 35.0% (control) to 13.0% (with methamidophos treatment) for C. plutellae; from 20.6% (control) to 9.0% (with methamidophos treatment) and from 24.3% (control) to 16.7% (with avermectin treatment) for D. rapae. The susceptibility to methamidophos of the resultant emerging adults of the two parasitoids was found to be significantly lower than that of the control when the parasitoids were left in contact with the same dosages of methamidophos. The average AChE activity inhibition by methamidophos and dichlorvos in 34,60 adults of the two parasitoids that emerged from the treatments (15.1% and 31.8% respectively for C. plutellae, and 21.1% and 26.9% for D. rapae) was also significantly lower than those of the controls (55.4% and 48.3% respectively for C. plutellae, and 42.9% and 51.7% for D. rapae). The bimolecular rate constant (ki) values of AChE to methamidophos and dichlorvos in the adults of parasitoids without the insecticide treatment were 1.78 and 1.56 times as high as those that emerged from the host insects treated with methamidophos for C. plutellae, and 1.91 and 1.66 times as high as those in the case of D. rapae. It is suggested that there is a difference in AChE sensitivity to insecticides between the resultant emerging parasitoids with and without insecticide pretreatment. Furthermore, the introduction of the insecticides to the host insects could be an important factor in the insecticide resistance development of the endoparasitoids. The natural selectivity would favour the parasitoids that had developed an insensitivity to the insecticide(s). Copyright © 2007 Society of Chemical Industry [source] Impact of spray application methodology on the development of resistance to cypermethrin and spinosad by fall armyworm Spodoptera frugiperda (JE Smith)PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2006Ali Al-Sarar Abstract The development of resistance to an insecticide under various types of application method has yet to be reported in the literature. Five fall armyworm Spodoptera armigera (JE Smith) colonies were reared in a chamber for ten generations before starting topical application bioassays. From each colony, 200,500 third,fourth-instar larvae were fed for 72 h on corn plants sprayed with cypermethrin or spinosad at minimum application rate (20 g ha,1) using a small droplet size nozzle XR8001VS (volume median diameter Dv0.5 = 163 µm) or a large droplet size nozzle XR8008VS (Dv0.5 = 519 µm). Surviving larvae were transferred to untreated corn leaves to complete their life cycle. Next-generation third-instar larvae of each colony were topically dosed with technical cypermethrin or spinosad at 1 µL per larva, and mortality was recorded 24 h post-treatment. The results indicated that cypermethrin demonstrated an insecticidal activity greater than that of spinosad, and the cypermethrin regression lines moved to the right faster than those for spinosad, indicating an increased tolerance of cypermethrin. Generally, larvae from all generations (F1,F7) under the XR8008VS treatments were less susceptible to cypermethrin and developed resistance faster and to higher levels than larvae from the XR8001VS treatments. The confidence limits (95%) of LD50 for all spinosad treatments indicated that there was no significant difference from the LD50 value of the susceptible reference strain. The results are a first indication that application technology/insecticide reaction may affect the rapidity of resistance development in certain pest/plant scenarios, but field studies are needed to confirm this conclusion. Copyright © 2006 Society of Chemical Industry [source] Herbicide resistance work in the United States Department of Agriculture,Agricultural Research Service,,PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 6-7 2003Kevin C Vaughn Abstract Herbicide-resistant weed biotypes are an increasing problem in agriculture, with reports of resistance to almost every herbicide class at some place in the world, and the total number of resistant biotypes at over 250. Agricultural Research Service (ARS) scientists have been key players in this area since the first substantiated occurrence of these resistant biotypes in the 1970s. The most significant of their contributions is the complete unraveling of the mechanism of triazine resistance by Arntzen and colleagues, then with ARS at the University of Illinois. These studies established a high benchmark for research in this area and are a model for all studies in this area. Other ARS scientists have investigated a large number of weed biotypes with resistance to a wide range of herbicide classes and mechanisms of resistance. Collectively, these studies have been used to generate herbicide resistance-management schemes for growers, based upon the herbicide site and the potential for resistance development. Published in 2003 for SCI by John Wiley & Sons, Ltd. [source] Laboratory studies to assess the risk of development of resistance to zoxamidePEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2001David H Young Abstract Laboratory studies were conducted to evaluate the risk of developing field resistance to zoxamide, a new Oomycete fungicide which acts on microtubules. Zoxamide, metalaxyl and dimethomorph were compared with respect to the ease with which fungicide-resistant mutants could be isolated and their level of resistance. Attempts to generate mutants of Phytophthora capsici and P infestans with resistance to zoxamide by mycelial adaptation on fungicide-amended medium were unsuccessful. Similarly, changes in sensitivity to zoxamide were small (resistance factors ,2.2) in mutants of P capsici isolated by chemical mutagenesis of zoospore cysts. In parallel experiments with metalaxyl, highly resistant mutants were obtained using both adaptation (P capsici or P infestans) and chemical mutagenesis (P capsici). For dimethomorph, chemical mutagenesis (P capsici) yielded moderately resistant mutants (maximum resistance factor,=,20.9), and adaptation (P capsici or P infestans) did not induce resistance. It is proposed that failure to isolate mutants resistant to zoxamide results from the diploid nature of Oomycete fungi and the likelihood that target-site mutations would produce a recessive phenotype. Our studies suggest that the risk of a highly resistant pathogen population developing rapidly in the field is much lower for zoxamide than for metalaxyl. However, as with any site-specific fungicide, appropriate precautions against resistance development should be taken. © 2001 Society of Chemical Industry [source] The ABC transporter BcatrB from Botrytis cinerea is a determinant of the activity of the phenylpyrrole fungicide fludioxonilPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 5 2001T Vermeulen Abstract This study demonstrates that the ATP-binding cassette (ABC) transporter BcatrB from Botrytis cinerea influences the activity of phenylpyrrole fungicides against the pathogen. This conclusion is based on toxicity assays and northern analysis experiments which show that BcatrB replacement mutants, which do not express the BcatrB gene, show an increased sensitivity to the phenylpyrrole fungicides fludioxonil and fenpiclonil. Mutants overexpressing BcatrB exhibit a decreased sensitivity to these fungicides. In addition, accumulation of fludioxonil by BcatrB replacement mutants was higher than by wild-type isolates. For mutants overexpressing BcatrB the reverse was observed. Additional ABC and major facilitator superfamily (MFS) transporter genes were identified in an expressed sequence tag (EST) database, suggesting that B cinerea has gene families of ABC and MFS transporters. Corresponding fragments of ten ABC (BcatrC,BcatrN) and three MFS transporter genes (Bcmfs1,4) were cloned and characterised. Fludioxonil affected the transcript level of some members of these gene families in germlings during a short treatment with the fungicide at sub-lethal concentrations. Hence, other ABC and MFS transporters may affect the activity of phenylpyrrole fungicides as well. Other fungicides such as the anilinopyrimidine fungicide cyprodinil, the azole fungicide tebuconazole, the dicarboximide fungicide iprodione and the strobilurin fungicide trifloxystrobin also induced transcription of some of the ABC and MFS transporter genes identified. Therefore, we propose that various ABC and MFS transporters function in protection of the fungus against fungicides and are involved in multi-drug resistance development. © 2001 Society of Chemical Industry [source] Sensitivity of Botrytis cinerea from vegetable greenhouses to boscalidPLANT PATHOLOGY, Issue 4 2007C. Q. Zhang Between 2004 and 2006, 228 isolates of Botrytis cinerea from two regions in China were characterized for baseline sensitivity to boscalid, a new active ingredient that interferes with succinate ubiquinone reductase in the electron transport chain. The isolates showed similar sensitivity in different years and regions. Baseline sensitivities were distributed as unimodal curves with mean EC50 values of 1·07 (± 0·11) and 0·42 (± 0·05) mg L,1 for inhibition of mycelial growth and conidial germination, respectively. Laboratory studies were conducted to evaluate the risk of development of resistance to boscalid. Boscalid-resistant mutants were obtained by UV-treatment at lower frequencies and with smaller resistance factors than pyrimethanil-resistant mutants. All boscalid-resistant mutants were also significantly more sensitive to Qo inhibitors than their wild-type parents and showed reduced sporulation in vitro and pathogenicity on aubergine leaves. The results suggested that the risk of resistance developing for boscalid was lower than for pyrimethanil. However, as B. cinerea is a high-risk pathogen, appropriate precautions against resistance development should be taken. Synergism between the activity of boscalid and that of kresoxim-methyl was observed. [source] Enzymatic and structural analysis of the I47A mutation contributing to the reduced susceptibility to HIV protease inhibitor lopinavirPROTEIN SCIENCE, Issue 9 2008Klára Grantz, ková Abstract Lopinavir (LPV) is a second-generation HIV protease inhibitor (PI) designed to overcome resistance development in patients undergoing long-term antiviral therapy. The mutation of isoleucine at position 47 of the HIV protease (PR) to alanine is associated with a high level of resistance to LPV. In this study, we show that recombinant PR containing a single I47A substitution has the inhibition constant (Ki) value for lopinavir by two orders of magnitude higher than for the wild-type PR. The addition of the I47A substitution to the background of a multiply mutated PR species from an AIDS patient showed a three-order-of-magnitude increase in Ki in vitro relative to the patient PR without the I47A mutation. The crystal structure of I47A PR in complex with LPV showed the loss of van der Waals interactions in the S2/S2, subsites. This is caused by the loss of three side-chain methyl groups due to the I47A substitution and by structural changes in the A47 main chain that lead to structural changes in the flap antiparallel ,-strand. Furthermore, we analyzed possible interaction of the I47A mutation with secondary mutations V32I and I54V. We show that both mutations in combination with I47A synergistically increase the relative resistance to LPV in vitro. The crystal structure of the I47A/I54V PR double mutant in complex with LPV shows that the I54V mutation leads to a compaction of the flap, and molecular modeling suggests that the introduction of the I54V mutation indirectly affects the strain of the bound inhibitor in the PR binding cleft. [source] Antimicrobial resistance 1979,2009 at Karolinska hospital, Sweden: normalized resistance interpretation during a 30-year follow-up on Staphylococcus aureus and Escherichia coli resistance developmentAPMIS, Issue 9 2010GÖRAN KRONVALL Kronvall G. Antimicrobial resistance 1979,2009 at Karolinska hospital, Sweden: normalized resistance interpretation during a 30-year follow-up on Staphylococcus aureus and Escherichia coli resistance development. APMIS 2010; 118: 621,39. To utilize a material of inhibition zone diameter measurements from disc diffusion susceptibility tests between 1979 and 2009, an objective setting of epidemiological breakpoints was necessary because of methodological changes. Normalized resistance interpretation (NRI) met this need and was applied to zone diameter histograms for Staphylococcus aureus and Escherichia coli isolates. The results confirmed a slow resistance development as seen in Northern countries. The S. aureus resistance levels for erythromycin, clindamycin and fusidic acid in 2009 were 3.2%, 1.8% and 1.4% with denominator correction. A rise in resistance to four antimicrobials in 1983 was probably because of a spread of resistant Methicillin Susceptible Staphylococcus Aureus (MSSA). For E. coli, the denominator-corrected resistance levels in 2009 were 27% for ampicillin, around 3% for third-generation cephalosporins, 0.1% for imipenem, 2.5% for gentamicin, 19% for trimethoprim, 4.5% for co-trimoxazole, 1.2% for nitrofurantoin and 9% for ciprofloxacin. The temporal trends showed a rise in fluoroquinolone resistance from 1993, a parallel increase in gentamicin resistance, a substantial increase in trimethoprim and sulphonamide resistance in spite of decreased consumption, and a steady rise in ampicillin resistance from a constant level before 1989. A short review of global resistance surveillance studies is included. [source] Photodynamic therapy: a targeted therapy in periodonticsAUSTRALIAN DENTAL JOURNAL, Issue 2009M Raghavendra Abstract The oral cavity is colonized by a large number and highly diversified communities of micro-organisms. Bacterial biofilm present on tooth or root surface is a major cause of gingivitis and periodontitis. Chemical antimicrobial agents are widely used in prophylactic and therapeutic regimens for dental plaque related diseases, which are among the most common human infections. As these agents are difficult to maintain at therapeutic concentrations in the oral cavity and can be rendered ineffective by resistance development in target organisms, there is a need for an alternative antimicrobial approach. A novel approach, photodynamic therapy (PDT), could be a solution to these problems. Lethal photosensitization of many bacteria, both Gram positive and Gram negative was found in many studies. The advantage of this new approach includes rapid bacterial elimination, minimal chance of resistance development and safety of adjacent host tissue and normal microflora. Thus, the available knowledge of photodynamic therapy should encourage a more clinically oriented application of this technique. [source] Emergence of CTX-M-15 extended-spectrum ,-lactamase-producing Klebsiella pneumoniae isolates in Bosnia and HerzegovinaCLINICAL MICROBIOLOGY AND INFECTION, Issue 2 2010A. Dedeic-Ljubovic Clin Microbiol Infect 2010; 16: 152,156 Abstract Fifty-seven nosocomial Klebsiella pneumoniae isolates producing extended-spectrum ,-lactamases (ESBLs) were collected between February 2007 and November 2007 in different wards of the Sarajevo (Bosnia-Herzegovina) reference hospital. These isolates comprise two major epidemic pulsed-field electrophoresis-defined clones plus two minor clones. In addition to the ESBL-mediated resistance, all strains uniformly showed resistance to ciprofloxacin, gentamicin and tobramycin. The ,-lactamases involved in this resistance phenotype were TEM-1, SHV-1, and CTX-M-15, as demonstrated by isoelectric focusing, PCR amplification, and sequencing. TEM-1 and CTX-M-15 ,-lactamases, as well as the aminoglycoside resistance determinants, were encoded in plasmids that could be transferred to Escherichia coli by conjugation. In three of the infected patients with the predominant clone, cefoxitin resistance development (MICs >128 mg/L) was documented. The analysis of the outer membrane proteins of the cefoxitin-susceptible and cefoxitin-resistant isolates revealed that the former expressed only one of the two major porins, OmpK36, whereas in the latter, the expression of Ompk36 was altered or abolished. This is the first report of CTX-M-15-producing K. pneumoniae in Bosnia-Herzegovina. Furthermore, we document and characterize for the first time cefoxitin resistance development in CTX-M-15-producing K. pneumoniae. [source] Problems of resistance development in arthropod pests of agricultural crops in RussiaEPPO BULLETIN, Issue 1 2008G. I. Sukhoruchenko This paper presents the results of long-term monitoring of insecticide resistance in populations of agricultural pests in Russia. Over the last 45 years, resistance developments were recorded for 36 arthropod pest species in 11 agricultural crops and pastures in relation to nearly all commonly used plant protection products. Development of group, cross and multiple resistance has been revealed in populations of many economically important pests. Toxicological and phenotypical (for Colorado potato beetle) methods have been devised to monitor the development of pesticide resistance. Based on experience over the last century, systems aimed at preventing the development of pest resistance to insecticides and acaricides are elaborated. These systems are based on resistance monitoring and using plant protection measures which minimize the toxic pressure on agroecosystems. [source] | ||||||||||||||||