The performance of antimicrobial susceptibility testing(AST)of bacteria and the interpretation of AST results for bacteria isolated from animals are complex tasks which must be performed using standard published metho...The performance of antimicrobial susceptibility testing(AST)of bacteria and the interpretation of AST results for bacteria isolated from animals are complex tasks which must be performed using standard published methodology and overseen by experts in clinical microbiology and in consultation with clinical pharmacologists.Otherwise,AST has significant potential for errors and mistakes.In this review,we provide guidance on how to correctly perform AST of bacteria isolated from animals and interpret the AST results.Particular emphasis is placed on the various approved or published methodologies for the different bacteria as well as the application of interpretive criteria,including clinical breakpoints and epidemiological cut-off values(ECVs/ECOFFs).Application of approved interpretive criteria and definitions of susceptible,susceptible dose-dependent,nonsusceptible,intermediate,and resistant for clinical breakpoints as well as wild-type and non-wildtype for ECVs,are explained and the difficulties resulting from the lack of approved clinical breakpoints for other bacteria,indications,and animal species is discussed.The requirement of quality controls in any AST approach is also emphasized.In addition,important parameters,often used in monitoring and surveillance studies,such as MIC50,MIC90,and testing range,are explained and criteria for the classification of bacteria as multidrug-resistant,extensively drug-resistant or pandrug-resistant are provided.Common mistakes are presented and the means to avoid them are described.To provide the most accurate AST,one must strictly adhere to approved standards or validated methodologies,like those of the Clinical and Laboratory Standards Institute or other internationally accepted AST documents and the detailed information provided therein.展开更多
Static fracture toughness characteristics are traditionally determined in tests of standard notched specimens using a P-V curve, where P is the load and V is the notch-opening displacement. This curve has a characteri...Static fracture toughness characteristics are traditionally determined in tests of standard notched specimens using a P-V curve, where P is the load and V is the notch-opening displacement. This curve has a characteristic point Q. At the load P<sub>Q</sub> corresponding to this point, the crack starts to propagate. For this load, the fracture toughness characteristics are then calculated. In brittle (elastic) fracture, the P-V curve at the onset of crack propagation has an extremum (or a local extremum), from whose ordinate PQ</sub> is determined with sufficient accuracy. In ductile and elastic-ductile fracture, P-V curves are monotonically increasing, and PQ</sub> is calculated using the 5% secant offset method without taking into account the characteristics of the material, so that the PQ</sub> is determined inaccurately. To improve the accuracy of PQ</sub> determination, we propose a thermographic method for determining the fracture toughness of metals. This method involves plotting the load P against the temperature change ΔТ over a relatively short period of time at the notch tip. This plot is then transformed to a P-ΔS curve, where ΔS is the specific entropy increment at the notch tip, which is calculated through ΔТ. This thermodynamic diagram has a characteristic step at the beginning of crack propagation, and from the ordinate of this step, PQ</sub> can be determined much more accurately. Furthermore, in the thermographic method, the preparation of test specimens can be simplified by replacing the process of growing a fatigue crack at the tip of a notch by making a sharp cut, which provides significant time savings. Statistical processing and comparison of test results of steel 20 specimens using the conventional and thermographic methods have shown the advantages of the thermographic method in accuracy and complexity.展开更多
文摘The performance of antimicrobial susceptibility testing(AST)of bacteria and the interpretation of AST results for bacteria isolated from animals are complex tasks which must be performed using standard published methodology and overseen by experts in clinical microbiology and in consultation with clinical pharmacologists.Otherwise,AST has significant potential for errors and mistakes.In this review,we provide guidance on how to correctly perform AST of bacteria isolated from animals and interpret the AST results.Particular emphasis is placed on the various approved or published methodologies for the different bacteria as well as the application of interpretive criteria,including clinical breakpoints and epidemiological cut-off values(ECVs/ECOFFs).Application of approved interpretive criteria and definitions of susceptible,susceptible dose-dependent,nonsusceptible,intermediate,and resistant for clinical breakpoints as well as wild-type and non-wildtype for ECVs,are explained and the difficulties resulting from the lack of approved clinical breakpoints for other bacteria,indications,and animal species is discussed.The requirement of quality controls in any AST approach is also emphasized.In addition,important parameters,often used in monitoring and surveillance studies,such as MIC50,MIC90,and testing range,are explained and criteria for the classification of bacteria as multidrug-resistant,extensively drug-resistant or pandrug-resistant are provided.Common mistakes are presented and the means to avoid them are described.To provide the most accurate AST,one must strictly adhere to approved standards or validated methodologies,like those of the Clinical and Laboratory Standards Institute or other internationally accepted AST documents and the detailed information provided therein.
文摘Static fracture toughness characteristics are traditionally determined in tests of standard notched specimens using a P-V curve, where P is the load and V is the notch-opening displacement. This curve has a characteristic point Q. At the load P<sub>Q</sub> corresponding to this point, the crack starts to propagate. For this load, the fracture toughness characteristics are then calculated. In brittle (elastic) fracture, the P-V curve at the onset of crack propagation has an extremum (or a local extremum), from whose ordinate PQ</sub> is determined with sufficient accuracy. In ductile and elastic-ductile fracture, P-V curves are monotonically increasing, and PQ</sub> is calculated using the 5% secant offset method without taking into account the characteristics of the material, so that the PQ</sub> is determined inaccurately. To improve the accuracy of PQ</sub> determination, we propose a thermographic method for determining the fracture toughness of metals. This method involves plotting the load P against the temperature change ΔТ over a relatively short period of time at the notch tip. This plot is then transformed to a P-ΔS curve, where ΔS is the specific entropy increment at the notch tip, which is calculated through ΔТ. This thermodynamic diagram has a characteristic step at the beginning of crack propagation, and from the ordinate of this step, PQ</sub> can be determined much more accurately. Furthermore, in the thermographic method, the preparation of test specimens can be simplified by replacing the process of growing a fatigue crack at the tip of a notch by making a sharp cut, which provides significant time savings. Statistical processing and comparison of test results of steel 20 specimens using the conventional and thermographic methods have shown the advantages of the thermographic method in accuracy and complexity.
