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Robert E. W. Hancock - One of the best experts on this subject based on the ideXlab platform.
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testing physiologically relevant conditions in minimal Inhibitory Concentration assays
Nature Protocols, 2021Co-Authors: Corrie R Belanger, Robert E. W. HancockAbstract:The minimal Inhibitory Concentration (MIC) assay uses agar or broth dilution methods to measure, under defined test conditions, the lowest effective Concentration of an antimicrobial agent that inhibits visible growth of a bacterium of interest. This assay is used to test the susceptibilities of bacterial isolates and of novel antimicrobial drugs, and is typically done in nutrient-rich laboratory media that have little relevance to in vivo conditions. As an extension to our original protocol on MIC assays (also published in Nature Protocols), here we describe the application of the MIC broth microdilution assay to test antimicrobial susceptibility in conditions that are more physiologically relevant to infections observed in the clinic. Specifically, we describe a platform that can be applied to the preparation of medium that mimics lung and wound exudate or blood conditions for the growth and susceptibility testing of bacteria, including ESKAPE pathogens. This protocol can also be applied to most physiologically relevant liquid medium and aerobic pathogens, and takes 3-4 d to complete.
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Agar and broth dilution methods to determine the minimal Inhibitory Concentration (MIC) of antimicrobial substances
Nature Protocols, 2008Co-Authors: Irith Wiegand, Kai Hilpert, Robert E. W. HancockAbstract:The aim of broth and agar dilution methods is to determine the lowest Concentration of the assayed antimicrobial agent (minimal Inhibitory Concentration, MIC) that, under defined test conditions, inhibits the visible growth of the bacterium being investigated. MIC values are used to determine susceptibilities of bacteria to drugs and also to evaluate the activity of new antimicrobial agents. Agar dilution involves the incorporation of different Concentrations of the antimicrobial substance into a nutrient agar medium followed by the application of a standardized number of cells to the surface of the agar plate. For broth dilution, often determined in 96-well microtiter plate format, bacteria are inoculated into a liquid growth medium in the presence of different Concentrations of an antimicrobial agent. Growth is assessed after incubation for a defined period of time (16–20 h) and the MIC value is read. This protocol applies only to aerobic bacteria and can be completed in 3 d.
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agar and broth dilution methods to determine the minimal Inhibitory Concentration mic of antimicrobial substances
Nature Protocols, 2008Co-Authors: Irith Wiegand, Kai Hilpert, Robert E. W. HancockAbstract:Agar and broth dilution methods to determine the minimal Inhibitory Concentration (MIC) of antimicrobial substances
Manel Almela - One of the best experts on this subject based on the ideXlab platform.
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epidemiology and prognosis of coagulase negative staphylococcal endocarditis impact of vancomycin minimum Inhibitory Concentration
PLOS ONE, 2015Co-Authors: Cristina Garcia De La Maria, Manel Almela, Carlos Cervera, Juan M Pericas, Ximena Castaneda, Y Armero, Dolors Soy, Salvador Ninot, Carlos Falces, Carlos A MestresAbstract:This study describes coagulase-negative staphylococcal (CoNS) infective endocarditis (IE) epidemiology at our institution, the antibiotic susceptibility profile, and the influence of vancomycin minimum Inhibitory Concentration (MIC) on patient outcomes. One hundred and three adults with definite IE admitted to an 850-bed tertiary care hospital in Barcelona from 1995-2008 were prospectively included in the cohort. We observed that CoNS IE was an important cause of community-acquired and healthcare-associated IE; one-third of patients involved native valves. Staphylococcus epidermidis was the most frequent species, methicillin-resistant in 52% of patients. CoNS frozen isolates were available in 88 patients. Vancomycin MICs of 2.0 μg/mL were common; almost all cases were found among S. epidermidis isolates and did not increase over time. Eighty-five patients were treated either with cloxacillin or vancomycin: 38 patients (Group 1) were treated with cloxacillin, and 47 received vancomycin; of these 47, 27 had CoNS isolates with a vancomycin MIC <2.0 μg/mL (Group 2), 20 had isolates with a vancomycin MIC ≥2.0 μg/mL (Group 3). One-year mortality was 21%, 48%, and 65% in Groups 1, 2, and 3, respectively (P=0.003). After adjusting for confounders and taking Group 2 as a reference, methicillin-susceptibility was associated with lower 1-year mortality (OR 0.12, 95% CI 0.02-0.55), and vancomycin MIC ≥2.0 μg/mL showed a trend to higher 1-year mortality (OR 3.7, 95% CI 0.9-15.2; P=0.069). Other independent variables associated with 1-year mortality were heart failure (OR 6.2, 95% CI 1.5-25.2) and pacemaker lead IE (OR 0.1, 95%CI 0.02-0.51). In conclusion, methicillin-resistant S.epidermidis was the leading cause of CoNS IE, and patients receiving vancomycin had higher mortality rates than those receiving cloxacillin; mortality was higher among patients having isolates with vancomycin MICs ≥2.0 μg/mL.
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effect of vancomycin minimal Inhibitory Concentration on the outcome of methicillin susceptible staphylococcus aureus endocarditis
Clinical Infectious Diseases, 2014Co-Authors: Carlos Cervera, Cristina Garcia De La Maria, Juan M Pericas, Ximena Castaneda, Y Armero, Dolors Soy, Carlos Falces, Ana Del Rio, Asuncion Moreno, Manel AlmelaAbstract:Background. Staphylococcus aureus endocarditis has a high mortality rate. Vancomycin minimum InhibitoryConcentration (MIC) has been shown to affect the outcome of methicillin-resistant S. aureus bacteremia, and recentdata point to a similareffect on methicillin-susceptible S. aureus bacteremia. We aimed to evaluate the effect of van-comycin MIC on left-sided S. aureus infective endocarditis (IE) treated with cloxacillin.Methods. We analyzed a prospectively collected cohort of patients with IE in a single tertiary-care hospital.Vancomycin, daptomycin,and cloxacillinMICwas determinedby E-test. S. aureus strainswere categorizedas low van-comycinMIC(<1.5 µg/mL)andhighvancomycinMIC(≥1.5 µg/mL).Theprimaryendpointwasin-hospitalmortality.Results. We analyzed 93 patients with left-sided IE treated with cloxacillin, of whom 53 (57%) had a vancomycinMIC<1.5 µg/mL and 40 (43%) avancomycin MIC≥1.5 µg/mL. In-hospital mortality was 30% (n=16/53) in patientswith a low vancomycin MIC and 53% (n=21/40) in those with a high vancomycin MIC (P=.03). No correlation wasfoundbetweenoxacillinMICandvancomycinordaptomycinMIC.Logisticregressionanalysisshowedthathighervan-comycin MIC increased in-hospital mortality 3-fold (odds ratio, 3.1; 95% confidence interval, 1.2–8.2) afteradjustmentfor age, year of diagnosis, septic complications, and nonseptic complicated endocarditis.Conclusions. OurresultsindicatethatvancomycinMICcouldbeusedtoidentifyasubgroupofpatientswithmeth-icillin-susceptibleS. aureus IEat riskof higher mortality. Theworse outcome of staphylococcal infectionswith a highervancomycin MIC cannot be explained solely by suboptimal pharmacokinetics of antibiotics.Keywords. methicillin-susceptible Staphylococcus aureus; left-sided endocarditis; cloxacillin; vancomycin min-imal Inhibitory Concentration; mortality.Staphylococcus aureusis the leading cause of infectiveendocarditis (IE) worldwide [1].Native-valve S. aureusendocarditis is more frequently caused by methicillin-susceptible S. aureus (MSSA) (85% of cases vs 15% inendocarditis caused by methicillin-resistant S.aureus[MRSA]), leading to a higher incidence of embolicevents, reduced need for surgery, and higher mortalitythan non–S. aureus native valve endocarditis [2]. De-spite considerable advances in diagnosis and surgicaland medical management, the in-hospital mortality ofMSSA endocarditis has remained unchanged at around25% in recent decades [2,3].In the last few years, several investigations have ad-dressed the issue of the high mortality associated withMRSA bacteremia. A higher vancomycin minimumInhibitory Concentration (MIC) has been shown toconfer a worse prognosis for MRSA bacteremia [4–6].
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influence of vancomycin minimum Inhibitory Concentration on the treatment of methicillin resistant staphylococcus aureus bacteremia
Clinical Infectious Diseases, 2008Co-Authors: Alex Soriano, Francesc Marco, Jose Antonio Baddini Martinez, Elena Pisos, Manel Almela, Veselka P Dimova, Dolores Alamo, Mar Ortega, J A Lopez, Josep MensaAbstract:BACKGROUND: Vancomycin treatment failure in methicillin-resistant Staphylococcus aureus (MRSA) bacteremia is not uncommon, even when MRSA is susceptible to vancomycin. The aim of our study was to evaluate whether vancomycin minimum Inhibitory Concentration has any influence on the mortality associated with MRSA bacteremia. METHODS: A total of 414 episodes of MRSA bacteremia were prospectively followed-up from 1991 through 2005. MIC of vancomycin for the first isolate was determined by E-test. Clinical variables recorded were age, comorbidity, prior administration of vancomycin, use of corticosteroids, prognosis of underlying disease, source of bacteremia, the need for mechanical ventilation, shock, and mortality. A "treatment group" variable was created and defined as follows: (1) receipt of empirical vancomycin and an isolate with a vancomycin MIC of 1 microg/mL (38 episodes), (2) receipt of empirical vancomycin and an isolate with a vancomycin MIC of 1.5 microg/mL (90 episodes), (3) receipt of empirical vancomycin and an isolate with a vancomycin MIC of 2 microg/mL (40 episodes), and (4) receipt of inappropriate empirical therapy (246 episodes). Univariate and multivariate analyses were performed. RESULTS: Episodes caused by strains with a vancomycin MIC of 2 microg/mL were independently associated with a lower risk of shock (odds ratio [OR], 0.33; 95% confidence interval [CI], 0.15-0.75). Multivariate analysis selected receipt of empirical vancomycin and an isolate with a vancomycin MIC of 2 microg/mL (OR, 6.39; 95% CI, 1.68-24.3), receipt of inappropriate empirical therapy (OR, 3.62; 95% CI, 1.20-10.9), increasing age (OR, 1.02; 95% CI, 1.00-1.04), use of corticosteroids (OR, 1.85; 95% CI, 1.04-3.29), an ultimately (OR, 10.2; 95% CI, 2.85-36.8) or rapidly (OR, 1.81; 95% CI, 1.06-3.10) fatal underlying disease, high-risk (OR, 3.60; 95% CI, 1.89-6.88) and intermediate-risk (OR, 2.18; 95% CI, 1.17-4.04) sources of bacteremia, and shock (OR, 7.38; 95% CI, 4.11-13.3) as the best predictors of mortality. CONCLUSIONS: Mortality associated with MRSA bacteremia was significantly higher when the empirical antibiotic was inappropriate and when vancomycin was empirically used for treatment of infection with strains with a high vancomycin MIC (>1 microg/mL).
Michael J Rybak - One of the best experts on this subject based on the ideXlab platform.
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early use of daptomycin versus vancomycin for methicillin resistant staphylococcus aureus bacteremia with vancomycin minimum Inhibitory Concentration 1 mg l a matched cohort study
Clinical Infectious Diseases, 2013Co-Authors: Kyle P Murray, Michael J Rybak, Jing J Zhao, Susan L Davis, Ravina Kullar, Keith S Kaye, Paul LephartAbstract:Background Recent reports have described decreased effectiveness with vancomycin treatment for methicillin-resistant Staphylococcus aureus bacteremia (MRSAB) when the vancomycin minimum Inhibitory Concentration (MIC) is >1 µg/mL. Methods This matched, retrospective cohort study compared the clinical effectiveness of daptomycin with that of vancomycin for the treatment of MRSAB with vancomycin MICs >1 µg/mL. The primary outcome was clinical failure, defined as a composite of 30-day mortality or bacteremia persisting for ≥7 days. Results One hundred seventy patients were matched 1:1 with respect to the antimicrobial administered. In the daptomycin group, all patients received Conclusions This is the first matched study comparing early daptomycin versus vancomycin for the treatment of MRSAB when the vancomycin MIC is >1 µg/mL. Treatment with daptomycin resulted in significantly improved outcomes, including decreased 30-day mortality and persistent bacteremia. These results support the practice of switching early from vancomycin to daptomycin for the treatment of MRSAB when the vancomycin MIC is >1 µg/mL.
Irith Wiegand - One of the best experts on this subject based on the ideXlab platform.
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Agar and broth dilution methods to determine the minimal Inhibitory Concentration (MIC) of antimicrobial substances
Nature Protocols, 2008Co-Authors: Irith Wiegand, Kai Hilpert, Robert E. W. HancockAbstract:The aim of broth and agar dilution methods is to determine the lowest Concentration of the assayed antimicrobial agent (minimal Inhibitory Concentration, MIC) that, under defined test conditions, inhibits the visible growth of the bacterium being investigated. MIC values are used to determine susceptibilities of bacteria to drugs and also to evaluate the activity of new antimicrobial agents. Agar dilution involves the incorporation of different Concentrations of the antimicrobial substance into a nutrient agar medium followed by the application of a standardized number of cells to the surface of the agar plate. For broth dilution, often determined in 96-well microtiter plate format, bacteria are inoculated into a liquid growth medium in the presence of different Concentrations of an antimicrobial agent. Growth is assessed after incubation for a defined period of time (16–20 h) and the MIC value is read. This protocol applies only to aerobic bacteria and can be completed in 3 d.
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agar and broth dilution methods to determine the minimal Inhibitory Concentration mic of antimicrobial substances
Nature Protocols, 2008Co-Authors: Irith Wiegand, Kai Hilpert, Robert E. W. HancockAbstract:Agar and broth dilution methods to determine the minimal Inhibitory Concentration (MIC) of antimicrobial substances
Carlos Cervera - One of the best experts on this subject based on the ideXlab platform.
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epidemiology and prognosis of coagulase negative staphylococcal endocarditis impact of vancomycin minimum Inhibitory Concentration
PLOS ONE, 2015Co-Authors: Cristina Garcia De La Maria, Manel Almela, Carlos Cervera, Juan M Pericas, Ximena Castaneda, Y Armero, Dolors Soy, Salvador Ninot, Carlos Falces, Carlos A MestresAbstract:This study describes coagulase-negative staphylococcal (CoNS) infective endocarditis (IE) epidemiology at our institution, the antibiotic susceptibility profile, and the influence of vancomycin minimum Inhibitory Concentration (MIC) on patient outcomes. One hundred and three adults with definite IE admitted to an 850-bed tertiary care hospital in Barcelona from 1995-2008 were prospectively included in the cohort. We observed that CoNS IE was an important cause of community-acquired and healthcare-associated IE; one-third of patients involved native valves. Staphylococcus epidermidis was the most frequent species, methicillin-resistant in 52% of patients. CoNS frozen isolates were available in 88 patients. Vancomycin MICs of 2.0 μg/mL were common; almost all cases were found among S. epidermidis isolates and did not increase over time. Eighty-five patients were treated either with cloxacillin or vancomycin: 38 patients (Group 1) were treated with cloxacillin, and 47 received vancomycin; of these 47, 27 had CoNS isolates with a vancomycin MIC <2.0 μg/mL (Group 2), 20 had isolates with a vancomycin MIC ≥2.0 μg/mL (Group 3). One-year mortality was 21%, 48%, and 65% in Groups 1, 2, and 3, respectively (P=0.003). After adjusting for confounders and taking Group 2 as a reference, methicillin-susceptibility was associated with lower 1-year mortality (OR 0.12, 95% CI 0.02-0.55), and vancomycin MIC ≥2.0 μg/mL showed a trend to higher 1-year mortality (OR 3.7, 95% CI 0.9-15.2; P=0.069). Other independent variables associated with 1-year mortality were heart failure (OR 6.2, 95% CI 1.5-25.2) and pacemaker lead IE (OR 0.1, 95%CI 0.02-0.51). In conclusion, methicillin-resistant S.epidermidis was the leading cause of CoNS IE, and patients receiving vancomycin had higher mortality rates than those receiving cloxacillin; mortality was higher among patients having isolates with vancomycin MICs ≥2.0 μg/mL.
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effect of vancomycin minimal Inhibitory Concentration on the outcome of methicillin susceptible staphylococcus aureus endocarditis
Clinical Infectious Diseases, 2014Co-Authors: Carlos Cervera, Cristina Garcia De La Maria, Juan M Pericas, Ximena Castaneda, Y Armero, Dolors Soy, Carlos Falces, Ana Del Rio, Asuncion Moreno, Manel AlmelaAbstract:Background. Staphylococcus aureus endocarditis has a high mortality rate. Vancomycin minimum InhibitoryConcentration (MIC) has been shown to affect the outcome of methicillin-resistant S. aureus bacteremia, and recentdata point to a similareffect on methicillin-susceptible S. aureus bacteremia. We aimed to evaluate the effect of van-comycin MIC on left-sided S. aureus infective endocarditis (IE) treated with cloxacillin.Methods. We analyzed a prospectively collected cohort of patients with IE in a single tertiary-care hospital.Vancomycin, daptomycin,and cloxacillinMICwas determinedby E-test. S. aureus strainswere categorizedas low van-comycinMIC(<1.5 µg/mL)andhighvancomycinMIC(≥1.5 µg/mL).Theprimaryendpointwasin-hospitalmortality.Results. We analyzed 93 patients with left-sided IE treated with cloxacillin, of whom 53 (57%) had a vancomycinMIC<1.5 µg/mL and 40 (43%) avancomycin MIC≥1.5 µg/mL. In-hospital mortality was 30% (n=16/53) in patientswith a low vancomycin MIC and 53% (n=21/40) in those with a high vancomycin MIC (P=.03). No correlation wasfoundbetweenoxacillinMICandvancomycinordaptomycinMIC.Logisticregressionanalysisshowedthathighervan-comycin MIC increased in-hospital mortality 3-fold (odds ratio, 3.1; 95% confidence interval, 1.2–8.2) afteradjustmentfor age, year of diagnosis, septic complications, and nonseptic complicated endocarditis.Conclusions. OurresultsindicatethatvancomycinMICcouldbeusedtoidentifyasubgroupofpatientswithmeth-icillin-susceptibleS. aureus IEat riskof higher mortality. Theworse outcome of staphylococcal infectionswith a highervancomycin MIC cannot be explained solely by suboptimal pharmacokinetics of antibiotics.Keywords. methicillin-susceptible Staphylococcus aureus; left-sided endocarditis; cloxacillin; vancomycin min-imal Inhibitory Concentration; mortality.Staphylococcus aureusis the leading cause of infectiveendocarditis (IE) worldwide [1].Native-valve S. aureusendocarditis is more frequently caused by methicillin-susceptible S. aureus (MSSA) (85% of cases vs 15% inendocarditis caused by methicillin-resistant S.aureus[MRSA]), leading to a higher incidence of embolicevents, reduced need for surgery, and higher mortalitythan non–S. aureus native valve endocarditis [2]. De-spite considerable advances in diagnosis and surgicaland medical management, the in-hospital mortality ofMSSA endocarditis has remained unchanged at around25% in recent decades [2,3].In the last few years, several investigations have ad-dressed the issue of the high mortality associated withMRSA bacteremia. A higher vancomycin minimumInhibitory Concentration (MIC) has been shown toconfer a worse prognosis for MRSA bacteremia [4–6].
