This work explores the potential of a triple combination of meropenem(MEM),a novel metallo-blactamase(MBL)inhibitor(indole-2-carboxylate 58(InC58)),and a serine-b-lactamase(SBL)inhibitor(avibactam(AVI))for broad-spect...This work explores the potential of a triple combination of meropenem(MEM),a novel metallo-blactamase(MBL)inhibitor(indole-2-carboxylate 58(InC58)),and a serine-b-lactamase(SBL)inhibitor(avibactam(AVI))for broad-spectrum activity against carbapenemase-producing bacteria.A diverse panel comprising MBL-and SBL-producing strains was used for susceptibility testing of the triple combination using the agar dilution method.The frequency of resistance(FoR)to MEM combined with InC58 was investigated.Mutants were sequenced and tested for cross resistance,fitness,and the stability of the resistance phenotype.Compared with the double combinations of MEM plus an SBL or MBL inhibitor,the triple combination extended the spectrum of activity to most of the isolates bearing SBLs(oxacillinase-48(OXA-48)and Klebsiella pneumoniae carbapenemase-2(KPC-2))and MBLs(New Delhi metallo-blactamases(NDMs)),although it was not effective against Verona integron-encoded metallo-blactamase(VIM)-carrying Pseudomonas aeruginosa(P.aeruginosa)and OXA-23-carrying Acinetobacter baumannii(A.baumannii).The FoR to MEM plus InC58 ranged from 2.22×10^(-7)to 1.13×10^(-6).The resistance correlated with mutations to ompC and comR,affecting porin C and copper permeability,respectively.The mutants manifested a fitness cost,a decreased level of resistance during passage without antibiotic pressure,and cross resistance to another carbapenem(imipenem)and a b-lactamase inhibitor(taniborbactam).In conclusion,compared with the dual combinations,the triple combination of MEM with InC58 and AVI showed a much wider spectrum of activity against different carbapenemaseproducing bacteria,revealing a new strategy to combat b-lactamase-mediated antimicrobial resistance.展开更多
Objective: Increasing the emergence of Metallo-β-lactamase (MBL) producing gram-negative bacteria and their dexterous horizontal transmission demands rapid and accurate detection. This study was conducted to determin...Objective: Increasing the emergence of Metallo-β-lactamase (MBL) producing gram-negative bacteria and their dexterous horizontal transmission demands rapid and accurate detection. This study was conducted to determine a suitable method to promptly detect MBL-producing gram-negative bacteria. Methods: A total of 103 gram-negative bacteria were identified from various clinical samples at a tertiary care hospital in Dhaka city. MBL producers were detected by two phenotypic methods, the Disk Potentiation Test (DPT) and the Double Disk Synergy Test (DDST) based on β-lactam chelator combinations where EDTA/SMA has been used as an inhibitor and Imipenem, Ceftazidime as substrates. Results: 103 isolates which were identified as Escherichia coli spp, Klebsiella spp, Pseudomonas spp, Acinetobacter spp, Proteus spp, Providencia spp were found to be multidrug-resistant in antibiogram test. Isolates showed complete resistance (100%) to Imipenem, Meropenem, and Amoxiclav. The highest carbapenem-resistant etiological agents were Acinetobacter spp 40 (38.8%) followed by Pseudomonas spp 27 (26.2%), Klebsiella spp 26 (25.2%), Escherichia coli 8 (7.8%), Proteus spp 1 (1%) and Providencia spp 1 (1%). DPT method detected significantly (p = 0.000009) a higher number of MBL-producers (Imipenem with 0.5 M EDTA n = 61, 59.2% & Ceftazidime with 0.5 M EDTA n = 56, 54.4%) compared to the DDST method (Imipenem -0.5 M EDTA n = 43, 41.7%, Imipenem – SMA n = 38, 36.9% & Ceftazidime -0.5 M EDTA n = 15, 14.6%). Conclusion: Pieces of evidence suggest that DPT is a more sensitive method than DDST and could be recommended for identifying MBL-producing bacteria in Bangladeshi hospitals for the proper management of patients, to reduce time constraints and treatment costs.展开更多
To investigate the distribution of the genes of two major metallo-β-1actamases (MBL;i.e.,IMP and VIM) and class 1 integrons (intI) in the clinical imipenem-resistant Pseudomonas aeruginosa, a total of 65 isolates...To investigate the distribution of the genes of two major metallo-β-1actamases (MBL;i.e.,IMP and VIM) and class 1 integrons (intI) in the clinical imipenem-resistant Pseudomonas aeruginosa, a total of 65 isolates, from a university hospital in Sichuan between December 2004 and April 2005 were screened for MBL genes by PCR using primers specific for blaIMP-1, blaVIM and blaVIM-2 genes. The MBL-positive isolates were further assessed for class 1 integrons by PCRusing specific primers. The nucleotide sequences of several PCR products were also determined. The results revealed that the blaVIM gene was found in 81.5% (53/65) of all isolates, blaVIM-2 gene was found in only 1 isolate and the intl gene was observed in 45.3% (24/53) of blaVIM-positive isolates. One isolate carried simultaneously both blaIMP-1 and intl genes, and to the best of our knowledge this is the first report of such isolate in southwest China. These observations highlight that the genes for VIM β-1actamase and class 1 integrons were predominantly present among the imipenem-resistant P. aeruginosa tested, confirming the current widespread threat of imipenem-resistant, integron-borne P.aeruginosa.展开更多
Thermal, mechanical and microstructural phenomena are involved in the process of steel quenching. Based on the coupled metallo-thermo-mechanics theory, a calculation model has been developed in this study to simulate ...Thermal, mechanical and microstructural phenomena are involved in the process of steel quenching. Based on the coupled metallo-thermo-mechanics theory, a calculation model has been developed in this study to simulate the quenching process of a gas turbine compressor disk by finite element method. The thermal physical and mechanical properties were treated as a functions of temperature. Moreover, a series of subroutines were developed on the MARC software platform. Consequently, simulated results on temperature, internal stress and distortion during the quenching were illustrated. With the aid of the simulated results, an optimum quenching scheme was proposed. The quenching process simulated in this study appears to be a promising tool in design of heat-treatment processing parameters for gas turbine compressor disks.展开更多
Objective:To detect and evaluate the various methods for metallo-β-lactamases(MBL) production in Pseudomonas aeruginosa(P.aeruginosa) and Acinetobacter species.Methods:A total of 109 P.aeruginosa and 85 Acinetobacter...Objective:To detect and evaluate the various methods for metallo-β-lactamases(MBL) production in Pseudomonas aeruginosa(P.aeruginosa) and Acinetobacter species.Methods:A total of 109 P.aeruginosa and 85 Acinetobacter species were screened for imipenem resistance by Kirby- Bauer disc diffusion methods.Detection of MBL production was(lone by imipenem-EDTA combined disc test,double disc synerygy test(DDST) and imipenem-EDTA MBL E test.Results: A total of 63(57.8%) strains of P.aeruginosa and 46(54.1%) strains of Acinetobacter spp.were found to be resistant to imipenem.Of the 63 imipenem resistant P.aeruginosa tested for MBL production.44(69.89;) were found to be positive and among 46 imipenem resistant Acinetobacter. 19(41.3%) were shown to be the MBL producers.Conclusions:Imipenem-EDTA combined disc test and MBL E test are equally effective for MBL detection in both P.aeruginosa and Acinetobacter spp.,but given the cost-constraints,combined disc can be used as a convenient screening method in the clinical microbiology laboratory.展开更多
Pseudomonas aeruginosa is a major cause of nosocomial infections with high mortality rates. The organism is highly resistant to most classes of drugs used and can develop resistance during treatment. One of the resist...Pseudomonas aeruginosa is a major cause of nosocomial infections with high mortality rates. The organism is highly resistant to most classes of drugs used and can develop resistance during treatment. One of the resistance mechanisms of P. aeruginosais is Metallo-β-Lactamase (MBL) production. MBL producing P. aeruginosa is a major health concern given it’s resistance to almost all available drugs. The prevalence of this resistant strain is unknown since there is no standardized method for testing MBL production. This was a laboratory based cross-sectional prospective study that was carried out from September 2015 to March 2016 at Kenyatta National Hospital. Ninety-nine isolates of P. aeruginosa were collected during the period and tested for antimicrobial susceptibility and isolates found to be resistant to imipenem tested for MBL production. The results indicated high resistance of P. aeruginosa to commonly used drugs. Of the isolates tested 69.7% were resistant to piperacillin, 63.6% were resistant to aztreonam, 58.6% were resistant to levofloxacin, 55.6% were resistant to cefipime, 65.7% were resistant to ceftazidime, 68.7% were resistant to ticarcillin-clavulanate, 72.2% were resistant to meropenem, 64.9% were resistance to imipenem while 86.4% of urine isolates were resistant to ofloxacin. Of the isolates resistant to imipenem 87.3% were found to be MBL producers. In conclusion, P. aeruginosais highly resistant to the drugs currently is used for treatment and resistance to carbapenems is largely due to MBL production.展开更多
The improper use of antimicrobials against infectious diseases has allowed microorganisms to develop defense mechanisms that give them insensitivity to these agents. All bacteria are concerned by this phenomenon. This...The improper use of antimicrobials against infectious diseases has allowed microorganisms to develop defense mechanisms that give them insensitivity to these agents. All bacteria are concerned by this phenomenon. This work aimed to assess prevalence of beta-lactamase produced by enterobacterial isolates. Then, disc diffusion, double disc synergy test (DDST) and combined disc test (CDT) were respectively used for antimicrobial resistance, detection of Extended-Spectrum Beta-Lactamases (ESBL) and Metallo-Beta-Lactamases (MBL). bla genes were detected by PCR. A total of 132 enterobacterial strains were studied. Resistance to antibiotic families was observed with a greater frequency than 50%. Gentamicin was the least active beta-lactam antibiotic, with a resistance rate of 88%. 40.9% of strains show an ESBL phenotype and 16.6% were MBL. An overall prevalence of 74% (40/54) and respectively rates of 29.6%, 27.7% and 16.7% for blaSHV, blaCTX and blaTEM genes were observed. SHV, CTX, CTX/SHV/TEM, CTX/TEM, SHV/TEM and CTX/SHV were different ESBL genotypes observed. ESBL-producing enterobacteria isolation worried about the future of antimicrobial therapy in the Republic of Congo. This is a public health problem that requires careful monitoring and implementation of a policy of rational antibiotics use.展开更多
In this work, the existence of interaction between metal in metallo enzyme and small biological molecules such as amino acid in aqueous solution is confirmed for the first time by the experimental data of ESR, NMR,UV-...In this work, the existence of interaction between metal in metallo enzyme and small biological molecules such as amino acid in aqueous solution is confirmed for the first time by the experimental data of ESR, NMR,UV-VIS and enzyme activity. This kind of interaction can affect the enzyme catalytic activity.展开更多
In intermediate-acid magmatic rocks,alkaline magmatic rocks,gneisses and migmatitic rocks K-feldspar is a rook-forming rock in which the contents of Pb are highest,just 2-10 times those of the whole rock,3-16 times th...In intermediate-acid magmatic rocks,alkaline magmatic rocks,gneisses and migmatitic rocks K-feldspar is a rook-forming rock in which the contents of Pb are highest,just 2-10 times those of the whole rock,3-16 times those of mica minerals and 6-32 times those of quartz.The lowest contents of K-feldspar are recognized in Early Proterozoic and Achaean rocks,with Pb in the K-feldspar accounting for less than 10% of that in the whole rock;in post-Middle Proterozoic alkaline magmatic rocks,K-feldspar-rich granites and metamorphic rocks the contents of K-feldspar tend to increase,with the proportion of Pb over that in the whole rock being obviously increased.In the alkaline rocks in which K-feldspar accounts for 50%-70%of the total in the whole rock,the contents of Pb in K-feldspar account approximately for 70%-95% of the total lead in the whole rock.Being accessible to hydrothermal alteration in the late periods,K-feldspar was conversed to sericite,calcite,quartz,etc.In the process of such conversion the lead would be leached out and then find its way into fluid phase.This kind of trans-formation can provide sufficent ore-forming material for later Pb metallogenesis.展开更多
The bacterial trialkyl-substituted aromatic polyketides are structurally featured with the unusual aromatic core in the middle of polyketide chain such as TM-123(1),veramycin A(2),NFAT-133(3)and benwamycin I(4),which ...The bacterial trialkyl-substituted aromatic polyketides are structurally featured with the unusual aromatic core in the middle of polyketide chain such as TM-123(1),veramycin A(2),NFAT-133(3)and benwamycin I(4),which were discovered from Streptomyces species and demonstrated with antidiabetic and immunosuppressant activities.Though the biosynthetic pathway of 1-3 was reported as a type I polyketide synthase(PKS),the PKS assembly line was interpreted inconsistently,and it remains a mystery how the compound 3 was generated.Herein,the PKS assembly logic of 1-4 was revised by site-mutagenetic analysis of the PKS dehydratase domains.Based on gene deletion and complementation,the putative P450 monooxygenase nftE1 and metallo-beta-lactamase(MBL)fold hydrolase nftF1 were verified as essential genes for the biosynthesis of 1-4.The absence of nftE1 led to abolishment of 1-4 and accumulation of new products(5-8).Structural elucidation reveals 5-8 as the non-aromatic analogs of 1,suggesting the NftE1-catalyzed aromatic core formation.Deletion of nftF1 resulted in disappearance of 3 and 4 with the compounds 1 and 2 unaffected.As a rare MBL-fold hydrolase from type I PKSs,NftF1 potentially generates the compound 3 through two strategies:catalyze premature chain-offloading as a trans-acting thioesterase or hydrolyze the lactone-bond of compound 1 as an esterase.展开更多
The problem of drug resistance of Gram-negative bacteria has become increasingly serious and has aroused widespread public concern.The "super bacteria" producing New Delhi metallo-beta-lactamase(NDM-1) are r...The problem of drug resistance of Gram-negative bacteria has become increasingly serious and has aroused widespread public concern.The "super bacteria" producing New Delhi metallo-beta-lactamase(NDM-1) are resistant to almost all β-lactam antibiotics.However, clinically existing β-lactamase inhibitors are ineffective against metallo-β-lactamases(MBLs) including NDM-1.Therefore, effective NDM-1 inhibitors are urgently needed.In this study, a high-throughput screening model for NDM-1 inhibitors was optimized and used to screen NDM-1 inhibitors.As a result, IMB-XH1 was screened out as a novel NDM-1 inhibitor from 52 100 compounds of different sources.The combined use of IMB-XH1 can increase the sensitivity of E.coli BL21(DE3)(pET-30 a(+)-NDM-1) to β-lactam antibiotics.Enzymatic kinetic studies indicate that IMB-XH1 is a non-competitive inhibitor of NDM-1 and also has inhibitory activity against other MBLs such as IMP-4, ImiS and L1.As a novel NDM-1 inhibitor, its activity and mechanism of action need to be further explored.展开更多
Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are believed to play important roles in the formation and regression of corpus luteum (CL). This study is to investigate the expression of gelatinas...Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are believed to play important roles in the formation and regression of corpus luteum (CL). This study is to investigate the expression of gelatinases (MMP-2, -9) and TIMPs in the rhesus monkey CL in both early and late luteal phases and during the early stages of pregnancy. Ovaries were collected from regularly cycling rhesus monkey at D5 and D15 following ovulation and at D12, D18 and D26 of pregnancy. In situ hybridization revealed that in the CL MMP-2 niRNA was expressed during both formation and regression, while MMP-9 mRNA was mainly localized in the late luteal phase. Reduction of MMP-2, -9 transcripts in the CL was observed during pregnancy. MMP-2 mRNA in the CL reduced to an undetectable level at D26 of pregnancy. TIMP-1 mRNA was highly expressed in the CL in both early and late luteal phases and persisted throughout the early stages of pregnancy. Strong signal for TIMP-2 mRNA was also detected in both luteal phases, and the展开更多
Background In the present study, we characterized multidrug-resistant Pseudomonas aeruginosa (MDRP) clinical isolates from a paediatric facility and investigated the types and features of the metallo-β-lactamases ...Background In the present study, we characterized multidrug-resistant Pseudomonas aeruginosa (MDRP) clinical isolates from a paediatric facility and investigated the types and features of the metallo-β-lactamases (MBLs) produced by carbapenem-resistant strains. Methods Four hundred and ninety-eight strains of Pseudomonas aeruginosa were isolated from patients at Beijing Children's Hospital between January 2005 and December 2006. The minimal inhibition concentrations (MICs) of the strains for 13 antibiotics were measured. A combination of the E test and PCR amplification/DNA sequencing was used to define the carbapenem-resistant strains. Results We found that 24.1% (120/498) of the isolates were MDRP. The frequencies of resistance to imipenem and meropenem were 34.2% and 35.8%, respectively, and the MIC50 and MIC90values for the two antibiotics were identical at 4 pg/ml and 32 pg/ml, respectively. The detection rate for carbapenem resistance was 49.2% (59/120). Among the 59 carbapenem-resistant Pseudomonas aeruginosa strains, 39 (66.1%) were positive for the MBL genotype; 35 (89.7%) strains carried the blaiMp gene and 4 (10.3%) strains carried the blavm gene. Neither blasPM nor blaGiM was amplified from any of the 59 isolates. DNA sequencing revealed that IMP-1 was present in 35 IMP-producing isolates and VIM-2 was detected in four VIM-producing isolates. Conclusions These MDRP isolates exhibited high frequencies of resistance to carbapenems among clinical isolates from a paediatric facility in Beijing, China. The production of MBL appears to be an important mechanism for carbapenem resistance in Pseudomonas aeruginosa.展开更多
Objective: To review the origin, diagnosis, treatment and public health concern of New Delhi metallo-β-lactamase (NDM)-producing bacteria. Data Sources: We searched database for studies published in English. The ...Objective: To review the origin, diagnosis, treatment and public health concern of New Delhi metallo-β-lactamase (NDM)-producing bacteria. Data Sources: We searched database for studies published in English. The database of PubMed from 2007 to 2015 was used to conduct a search using the keyword term "NDM and Acinetobacter or Enterobacteriaceae or Pseudomonas aeruginosa." Study Selection: We collected data including the relevant articles on international transmission, testing methods and treatment strategies of NDM-positive bacteria. Worldwide NDM cases were reviewed based on 22 case reports. Results: The first documented case of infection caused by bacteria producing NDM- 1 occurred in India, in 2008. Since then, 13 blaNDM variants have been reported. The rise of NDM is not only due to its high rate of genetic transfer among unrelated bacterial species, but also to human factors such as travel, sanitation and food production and preparation. With limited treatment options, scientists try to improve available therapies and create new ones. Conclusions: In order to slow down the spread of these NDM-positive bacteria, a series of measures must be implemented. The creation and transmission of blaNDM are potentially global health issues, which are not issues for one country or one medical community, but for global priorities in general and for individual wound care practitioners specifically.展开更多
New Delhi metallo-b-lactmase-1(NDM-1) catalyzes the hydrolysis of b-lactam antibiotics and cleaves the b-lactam ring of the molecule, conferring bacterial resistance against these medicines. In an effort to discover...New Delhi metallo-b-lactmase-1(NDM-1) catalyzes the hydrolysis of b-lactam antibiotics and cleaves the b-lactam ring of the molecule, conferring bacterial resistance against these medicines. In an effort to discover novel agents to treat this superbug, an old drug methisazone was found to be a weak NDM-1 inhibitor, with an IC50 of 297.6 mmol/L. Based on this result, a series of isatin-β-thiosemicarbazones(IBTs)were synthesized and biologically evaluated as novel NDM-1 inhibitors. Nine of the IBT compounds showed IC50 values of 〈10 mmol/L, the best of which was 2.72 mmol/L. Comparative field analysis(Co MFA) contour maps were generated to depict the structural features and molecular docking was performed to understand the possible binding mode of these inhibitors. The present research hereby has provided valuable information for further discovery of NDM-1 inhibitors.展开更多
In an effort to understand the recombination of a B2 metallo-β-lactamase(MβL),the binding of metals to apo-ImiS was studied by isothermal titration calorimetry and fluorescence spectra.The binding of Zn(Ⅱ),Co...In an effort to understand the recombination of a B2 metallo-β-lactamase(MβL),the binding of metals to apo-ImiS was studied by isothermal titration calorimetry and fluorescence spectra.The binding of Zn(Ⅱ),Co(Ⅱ) to apo-lmiS resulted in activation free energies △G_≠~θ values of 93.719 and 92.948 kJ mol^(-1),respectively,and increasing of fluorescence intensity at maxima emission of 340 nm.展开更多
基金supported by the Ineos Oxford Institute for Antimicrobial Research,the Biotechnology and Biological Sciences Research Council(BB/V003291/1)the WellcomeTrust(106244/Z/14/Z).
文摘This work explores the potential of a triple combination of meropenem(MEM),a novel metallo-blactamase(MBL)inhibitor(indole-2-carboxylate 58(InC58)),and a serine-b-lactamase(SBL)inhibitor(avibactam(AVI))for broad-spectrum activity against carbapenemase-producing bacteria.A diverse panel comprising MBL-and SBL-producing strains was used for susceptibility testing of the triple combination using the agar dilution method.The frequency of resistance(FoR)to MEM combined with InC58 was investigated.Mutants were sequenced and tested for cross resistance,fitness,and the stability of the resistance phenotype.Compared with the double combinations of MEM plus an SBL or MBL inhibitor,the triple combination extended the spectrum of activity to most of the isolates bearing SBLs(oxacillinase-48(OXA-48)and Klebsiella pneumoniae carbapenemase-2(KPC-2))and MBLs(New Delhi metallo-blactamases(NDMs)),although it was not effective against Verona integron-encoded metallo-blactamase(VIM)-carrying Pseudomonas aeruginosa(P.aeruginosa)and OXA-23-carrying Acinetobacter baumannii(A.baumannii).The FoR to MEM plus InC58 ranged from 2.22×10^(-7)to 1.13×10^(-6).The resistance correlated with mutations to ompC and comR,affecting porin C and copper permeability,respectively.The mutants manifested a fitness cost,a decreased level of resistance during passage without antibiotic pressure,and cross resistance to another carbapenem(imipenem)and a b-lactamase inhibitor(taniborbactam).In conclusion,compared with the dual combinations,the triple combination of MEM with InC58 and AVI showed a much wider spectrum of activity against different carbapenemaseproducing bacteria,revealing a new strategy to combat b-lactamase-mediated antimicrobial resistance.
文摘Objective: Increasing the emergence of Metallo-β-lactamase (MBL) producing gram-negative bacteria and their dexterous horizontal transmission demands rapid and accurate detection. This study was conducted to determine a suitable method to promptly detect MBL-producing gram-negative bacteria. Methods: A total of 103 gram-negative bacteria were identified from various clinical samples at a tertiary care hospital in Dhaka city. MBL producers were detected by two phenotypic methods, the Disk Potentiation Test (DPT) and the Double Disk Synergy Test (DDST) based on β-lactam chelator combinations where EDTA/SMA has been used as an inhibitor and Imipenem, Ceftazidime as substrates. Results: 103 isolates which were identified as Escherichia coli spp, Klebsiella spp, Pseudomonas spp, Acinetobacter spp, Proteus spp, Providencia spp were found to be multidrug-resistant in antibiogram test. Isolates showed complete resistance (100%) to Imipenem, Meropenem, and Amoxiclav. The highest carbapenem-resistant etiological agents were Acinetobacter spp 40 (38.8%) followed by Pseudomonas spp 27 (26.2%), Klebsiella spp 26 (25.2%), Escherichia coli 8 (7.8%), Proteus spp 1 (1%) and Providencia spp 1 (1%). DPT method detected significantly (p = 0.000009) a higher number of MBL-producers (Imipenem with 0.5 M EDTA n = 61, 59.2% & Ceftazidime with 0.5 M EDTA n = 56, 54.4%) compared to the DDST method (Imipenem -0.5 M EDTA n = 43, 41.7%, Imipenem – SMA n = 38, 36.9% & Ceftazidime -0.5 M EDTA n = 15, 14.6%). Conclusion: Pieces of evidence suggest that DPT is a more sensitive method than DDST and could be recommended for identifying MBL-producing bacteria in Bangladeshi hospitals for the proper management of patients, to reduce time constraints and treatment costs.
基金a grant from National Natu-ral Science Foundation of China (No. 30370079)
文摘To investigate the distribution of the genes of two major metallo-β-1actamases (MBL;i.e.,IMP and VIM) and class 1 integrons (intI) in the clinical imipenem-resistant Pseudomonas aeruginosa, a total of 65 isolates, from a university hospital in Sichuan between December 2004 and April 2005 were screened for MBL genes by PCR using primers specific for blaIMP-1, blaVIM and blaVIM-2 genes. The MBL-positive isolates were further assessed for class 1 integrons by PCRusing specific primers. The nucleotide sequences of several PCR products were also determined. The results revealed that the blaVIM gene was found in 81.5% (53/65) of all isolates, blaVIM-2 gene was found in only 1 isolate and the intl gene was observed in 45.3% (24/53) of blaVIM-positive isolates. One isolate carried simultaneously both blaIMP-1 and intl genes, and to the best of our knowledge this is the first report of such isolate in southwest China. These observations highlight that the genes for VIM β-1actamase and class 1 integrons were predominantly present among the imipenem-resistant P. aeruginosa tested, confirming the current widespread threat of imipenem-resistant, integron-borne P.aeruginosa.
文摘Thermal, mechanical and microstructural phenomena are involved in the process of steel quenching. Based on the coupled metallo-thermo-mechanics theory, a calculation model has been developed in this study to simulate the quenching process of a gas turbine compressor disk by finite element method. The thermal physical and mechanical properties were treated as a functions of temperature. Moreover, a series of subroutines were developed on the MARC software platform. Consequently, simulated results on temperature, internal stress and distortion during the quenching were illustrated. With the aid of the simulated results, an optimum quenching scheme was proposed. The quenching process simulated in this study appears to be a promising tool in design of heat-treatment processing parameters for gas turbine compressor disks.
文摘Objective:To detect and evaluate the various methods for metallo-β-lactamases(MBL) production in Pseudomonas aeruginosa(P.aeruginosa) and Acinetobacter species.Methods:A total of 109 P.aeruginosa and 85 Acinetobacter species were screened for imipenem resistance by Kirby- Bauer disc diffusion methods.Detection of MBL production was(lone by imipenem-EDTA combined disc test,double disc synerygy test(DDST) and imipenem-EDTA MBL E test.Results: A total of 63(57.8%) strains of P.aeruginosa and 46(54.1%) strains of Acinetobacter spp.were found to be resistant to imipenem.Of the 63 imipenem resistant P.aeruginosa tested for MBL production.44(69.89;) were found to be positive and among 46 imipenem resistant Acinetobacter. 19(41.3%) were shown to be the MBL producers.Conclusions:Imipenem-EDTA combined disc test and MBL E test are equally effective for MBL detection in both P.aeruginosa and Acinetobacter spp.,but given the cost-constraints,combined disc can be used as a convenient screening method in the clinical microbiology laboratory.
文摘Pseudomonas aeruginosa is a major cause of nosocomial infections with high mortality rates. The organism is highly resistant to most classes of drugs used and can develop resistance during treatment. One of the resistance mechanisms of P. aeruginosais is Metallo-β-Lactamase (MBL) production. MBL producing P. aeruginosa is a major health concern given it’s resistance to almost all available drugs. The prevalence of this resistant strain is unknown since there is no standardized method for testing MBL production. This was a laboratory based cross-sectional prospective study that was carried out from September 2015 to March 2016 at Kenyatta National Hospital. Ninety-nine isolates of P. aeruginosa were collected during the period and tested for antimicrobial susceptibility and isolates found to be resistant to imipenem tested for MBL production. The results indicated high resistance of P. aeruginosa to commonly used drugs. Of the isolates tested 69.7% were resistant to piperacillin, 63.6% were resistant to aztreonam, 58.6% were resistant to levofloxacin, 55.6% were resistant to cefipime, 65.7% were resistant to ceftazidime, 68.7% were resistant to ticarcillin-clavulanate, 72.2% were resistant to meropenem, 64.9% were resistance to imipenem while 86.4% of urine isolates were resistant to ofloxacin. Of the isolates resistant to imipenem 87.3% were found to be MBL producers. In conclusion, P. aeruginosais highly resistant to the drugs currently is used for treatment and resistance to carbapenems is largely due to MBL production.
文摘The improper use of antimicrobials against infectious diseases has allowed microorganisms to develop defense mechanisms that give them insensitivity to these agents. All bacteria are concerned by this phenomenon. This work aimed to assess prevalence of beta-lactamase produced by enterobacterial isolates. Then, disc diffusion, double disc synergy test (DDST) and combined disc test (CDT) were respectively used for antimicrobial resistance, detection of Extended-Spectrum Beta-Lactamases (ESBL) and Metallo-Beta-Lactamases (MBL). bla genes were detected by PCR. A total of 132 enterobacterial strains were studied. Resistance to antibiotic families was observed with a greater frequency than 50%. Gentamicin was the least active beta-lactam antibiotic, with a resistance rate of 88%. 40.9% of strains show an ESBL phenotype and 16.6% were MBL. An overall prevalence of 74% (40/54) and respectively rates of 29.6%, 27.7% and 16.7% for blaSHV, blaCTX and blaTEM genes were observed. SHV, CTX, CTX/SHV/TEM, CTX/TEM, SHV/TEM and CTX/SHV were different ESBL genotypes observed. ESBL-producing enterobacteria isolation worried about the future of antimicrobial therapy in the Republic of Congo. This is a public health problem that requires careful monitoring and implementation of a policy of rational antibiotics use.
文摘In this work, the existence of interaction between metal in metallo enzyme and small biological molecules such as amino acid in aqueous solution is confirmed for the first time by the experimental data of ESR, NMR,UV-VIS and enzyme activity. This kind of interaction can affect the enzyme catalytic activity.
文摘In intermediate-acid magmatic rocks,alkaline magmatic rocks,gneisses and migmatitic rocks K-feldspar is a rook-forming rock in which the contents of Pb are highest,just 2-10 times those of the whole rock,3-16 times those of mica minerals and 6-32 times those of quartz.The lowest contents of K-feldspar are recognized in Early Proterozoic and Achaean rocks,with Pb in the K-feldspar accounting for less than 10% of that in the whole rock;in post-Middle Proterozoic alkaline magmatic rocks,K-feldspar-rich granites and metamorphic rocks the contents of K-feldspar tend to increase,with the proportion of Pb over that in the whole rock being obviously increased.In the alkaline rocks in which K-feldspar accounts for 50%-70%of the total in the whole rock,the contents of Pb in K-feldspar account approximately for 70%-95% of the total lead in the whole rock.Being accessible to hydrothermal alteration in the late periods,K-feldspar was conversed to sericite,calcite,quartz,etc.In the process of such conversion the lead would be leached out and then find its way into fluid phase.This kind of trans-formation can provide sufficent ore-forming material for later Pb metallogenesis.
基金the National Natural Science Foundation of China(Nos.32070070,32211530074 and 31929001)the innovative research team of high-level local universities in Shanghai.H.D.thanks Royal Society-NSFC international exchange grant(IEC\NSFC\211349).
文摘The bacterial trialkyl-substituted aromatic polyketides are structurally featured with the unusual aromatic core in the middle of polyketide chain such as TM-123(1),veramycin A(2),NFAT-133(3)and benwamycin I(4),which were discovered from Streptomyces species and demonstrated with antidiabetic and immunosuppressant activities.Though the biosynthetic pathway of 1-3 was reported as a type I polyketide synthase(PKS),the PKS assembly line was interpreted inconsistently,and it remains a mystery how the compound 3 was generated.Herein,the PKS assembly logic of 1-4 was revised by site-mutagenetic analysis of the PKS dehydratase domains.Based on gene deletion and complementation,the putative P450 monooxygenase nftE1 and metallo-beta-lactamase(MBL)fold hydrolase nftF1 were verified as essential genes for the biosynthesis of 1-4.The absence of nftE1 led to abolishment of 1-4 and accumulation of new products(5-8).Structural elucidation reveals 5-8 as the non-aromatic analogs of 1,suggesting the NftE1-catalyzed aromatic core formation.Deletion of nftF1 resulted in disappearance of 3 and 4 with the compounds 1 and 2 unaffected.As a rare MBL-fold hydrolase from type I PKSs,NftF1 potentially generates the compound 3 through two strategies:catalyze premature chain-offloading as a trans-acting thioesterase or hydrolyze the lactone-bond of compound 1 as an esterase.
基金Natural Sciences Foundation of China(NSFC,Grant No.81872913)the CAMS Initiative for Innovative Medicine(Grant No.2016-I2M-1-013)+1 种基金the Fundamental Research Funds for Central Public-interest Scientific Institution(Centre for Tuberculosis)(Grant No.2016ZX310183-3)the National High-tech R&D Program(863 Program,Grant No.2015AA020911)
文摘The problem of drug resistance of Gram-negative bacteria has become increasingly serious and has aroused widespread public concern.The "super bacteria" producing New Delhi metallo-beta-lactamase(NDM-1) are resistant to almost all β-lactam antibiotics.However, clinically existing β-lactamase inhibitors are ineffective against metallo-β-lactamases(MBLs) including NDM-1.Therefore, effective NDM-1 inhibitors are urgently needed.In this study, a high-throughput screening model for NDM-1 inhibitors was optimized and used to screen NDM-1 inhibitors.As a result, IMB-XH1 was screened out as a novel NDM-1 inhibitor from 52 100 compounds of different sources.The combined use of IMB-XH1 can increase the sensitivity of E.coli BL21(DE3)(pET-30 a(+)-NDM-1) to β-lactam antibiotics.Enzymatic kinetic studies indicate that IMB-XH1 is a non-competitive inhibitor of NDM-1 and also has inhibitory activity against other MBLs such as IMP-4, ImiS and L1.As a novel NDM-1 inhibitor, its activity and mechanism of action need to be further explored.
基金This work was supported by the "95" National"Climbing Project" and the Knowledge Innovation Project of the Chinese Academy of Sciences.
文摘Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are believed to play important roles in the formation and regression of corpus luteum (CL). This study is to investigate the expression of gelatinases (MMP-2, -9) and TIMPs in the rhesus monkey CL in both early and late luteal phases and during the early stages of pregnancy. Ovaries were collected from regularly cycling rhesus monkey at D5 and D15 following ovulation and at D12, D18 and D26 of pregnancy. In situ hybridization revealed that in the CL MMP-2 niRNA was expressed during both formation and regression, while MMP-9 mRNA was mainly localized in the late luteal phase. Reduction of MMP-2, -9 transcripts in the CL was observed during pregnancy. MMP-2 mRNA in the CL reduced to an undetectable level at D26 of pregnancy. TIMP-1 mRNA was highly expressed in the CL in both early and late luteal phases and persisted throughout the early stages of pregnancy. Strong signal for TIMP-2 mRNA was also detected in both luteal phases, and the
文摘Background In the present study, we characterized multidrug-resistant Pseudomonas aeruginosa (MDRP) clinical isolates from a paediatric facility and investigated the types and features of the metallo-β-lactamases (MBLs) produced by carbapenem-resistant strains. Methods Four hundred and ninety-eight strains of Pseudomonas aeruginosa were isolated from patients at Beijing Children's Hospital between January 2005 and December 2006. The minimal inhibition concentrations (MICs) of the strains for 13 antibiotics were measured. A combination of the E test and PCR amplification/DNA sequencing was used to define the carbapenem-resistant strains. Results We found that 24.1% (120/498) of the isolates were MDRP. The frequencies of resistance to imipenem and meropenem were 34.2% and 35.8%, respectively, and the MIC50 and MIC90values for the two antibiotics were identical at 4 pg/ml and 32 pg/ml, respectively. The detection rate for carbapenem resistance was 49.2% (59/120). Among the 59 carbapenem-resistant Pseudomonas aeruginosa strains, 39 (66.1%) were positive for the MBL genotype; 35 (89.7%) strains carried the blaiMp gene and 4 (10.3%) strains carried the blavm gene. Neither blasPM nor blaGiM was amplified from any of the 59 isolates. DNA sequencing revealed that IMP-1 was present in 35 IMP-producing isolates and VIM-2 was detected in four VIM-producing isolates. Conclusions These MDRP isolates exhibited high frequencies of resistance to carbapenems among clinical isolates from a paediatric facility in Beijing, China. The production of MBL appears to be an important mechanism for carbapenem resistance in Pseudomonas aeruginosa.
基金Source of Support: This study was supported by grants from National Natural Science Foundation of China (No. 81101288 and 81172737). Conflict of Interest: None declared.
文摘Objective: To review the origin, diagnosis, treatment and public health concern of New Delhi metallo-β-lactamase (NDM)-producing bacteria. Data Sources: We searched database for studies published in English. The database of PubMed from 2007 to 2015 was used to conduct a search using the keyword term "NDM and Acinetobacter or Enterobacteriaceae or Pseudomonas aeruginosa." Study Selection: We collected data including the relevant articles on international transmission, testing methods and treatment strategies of NDM-positive bacteria. Worldwide NDM cases were reviewed based on 22 case reports. Results: The first documented case of infection caused by bacteria producing NDM- 1 occurred in India, in 2008. Since then, 13 blaNDM variants have been reported. The rise of NDM is not only due to its high rate of genetic transfer among unrelated bacterial species, but also to human factors such as travel, sanitation and food production and preparation. With limited treatment options, scientists try to improve available therapies and create new ones. Conclusions: In order to slow down the spread of these NDM-positive bacteria, a series of measures must be implemented. The creation and transmission of blaNDM are potentially global health issues, which are not issues for one country or one medical community, but for global priorities in general and for individual wound care practitioners specifically.
基金supported by the “111” Project of Ministry of Education of China (No. B06005)the National Natural Science Foundation of China (No. 21672114)the National Basic Research Program of China (No. 2013CB734004)
文摘New Delhi metallo-b-lactmase-1(NDM-1) catalyzes the hydrolysis of b-lactam antibiotics and cleaves the b-lactam ring of the molecule, conferring bacterial resistance against these medicines. In an effort to discover novel agents to treat this superbug, an old drug methisazone was found to be a weak NDM-1 inhibitor, with an IC50 of 297.6 mmol/L. Based on this result, a series of isatin-β-thiosemicarbazones(IBTs)were synthesized and biologically evaluated as novel NDM-1 inhibitors. Nine of the IBT compounds showed IC50 values of 〈10 mmol/L, the best of which was 2.72 mmol/L. Comparative field analysis(Co MFA) contour maps were generated to depict the structural features and molecular docking was performed to understand the possible binding mode of these inhibitors. The present research hereby has provided valuable information for further discovery of NDM-1 inhibitors.
基金supported by the National Natural Science Foundation of China (Nos.21272186 and 81361138018)
文摘In an effort to understand the recombination of a B2 metallo-β-lactamase(MβL),the binding of metals to apo-ImiS was studied by isothermal titration calorimetry and fluorescence spectra.The binding of Zn(Ⅱ),Co(Ⅱ) to apo-lmiS resulted in activation free energies △G_≠~θ values of 93.719 and 92.948 kJ mol^(-1),respectively,and increasing of fluorescence intensity at maxima emission of 340 nm.