Agar and broth dilution methods to determine the minimal inhibitory concentration (MIC) of antimicrobial substances
TL;DR: 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.
Abstract: 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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TL;DR: The final objective is to implement wastewater treatment technologies capable of assuring the production of UWTPs effluents with an acceptable level of ARB, to understand the factors and mechanisms that drive antibiotic resistance maintenance and selection in wastewater habitats.
1,808 citations
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...Antibiotic resistance testing is highly standardized worldwide, enabling laboratories to assist clinicians in bacterial infection therapy (CLSI, 2007; WHO, 2008; Wiegand et al., 2008)....
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TL;DR: This Opinion article describes recent studies of tolerance, resistance and persistence, outlining how a clear and distinct definition for each phenotype can be developed from these findings and proposes a framework for classifying the drug response of bacterial strains according to these definitions that is based on the measurement of the minimum inhibitory concentration.
Abstract: Antibiotic tolerance is associated with the failure of antibiotic treatment and the relapse of many bacterial infections. However, unlike resistance, which is commonly measured using the minimum inhibitory concentration (MIC) metric, tolerance is poorly characterized, owing to the lack of a similar quantitative indicator. This may lead to the misclassification of tolerant strains as resistant, or vice versa, and result in ineffective treatments. In this Opinion article, we describe recent studies of tolerance, resistance and persistence, outlining how a clear and distinct definition for each phenotype can be developed from these findings. We propose a framework for classifying the drug response of bacterial strains according to these definitions that is based on the measurement of the MIC together with a recently defined quantitative indicator of tolerance, the minimum duration for killing (MDK). Finally, we discuss genes that are associated with increased tolerance - the 'tolerome' - as targets for treating tolerant bacterial strains.
1,019 citations
TL;DR: An "interfacial activity model" is proposed, which is based on an experimentally testable molecular image of AMP-membrane interactions, which may be useful in driving engineering and design of novel AMPs.
Abstract: Antimicrobial peptides (AMPs) have been studied for three decades, and yet a molecular understanding of their mechanism of action is still lacking. Here we summarize current knowledge for both synthetic vesicle experiments and microbe experiments, with a focus on comparisons between the two. Microbial experiments are done at peptide to lipid ratios that are at least 4 orders of magnitude higher than vesicle-based experiments. To close the gap between the two concentration regimes, we propose an “interfacial activity model”, which is based on an experimentally testable molecular image of AMP–membrane interactions. The interfacial activity model may be useful in driving engineering and design of novel AMPs.
788 citations
Cites methods from "Agar and broth dilution methods to ..."
...Biological assays are carried out at 104–106 bacterial cells mL 1 (58)....
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TL;DR: In this paper, an eco-friendly, cost efficient, rapid and easy method for synthesis of silver nanoparticles using banana peel extract (BPE) as a reducing and capping agent was reported.
676 citations
TL;DR: Joint collaboration across the world with international bodies is needed to assist the developing countries to implement good surveillance of antibiotic use and antibiotic resistance, and strengthening of regulations that direct antibiotic manufacture, distribution, dispensing, and prescription is needed, hence fostering antibiotic stewardship.
Abstract: Due to the increased demand of animal protein in developing countries, intensive farming is instigated, which results in antibiotic residues in animal-derived products, and eventually, antibiotic resistance. Antibiotic resistance is of great public health concern because the antibiotic-resistant bacteria associated with the animals may be pathogenic to humans, easily transmitted to humans via food chains, and widely disseminated in the environment via animal wastes. These may cause complicated, untreatable, and prolonged infections in humans, leading to higher healthcare cost and sometimes death. In the said countries, antibiotic resistance is so complex and difficult, due to irrational use of antibiotics both in the clinical and agriculture settings, low socioeconomic status, poor sanitation and hygienic status, as well as that zoonotic bacterial pathogens are not regularly cultured, and their resistance to commonly used antibiotics are scarcely investigated (poor surveillance systems). The challenges that follow are of local, national, regional, and international dimensions, as there are no geographic boundaries to impede the spread of antibiotic resistance. In addition, the information assembled in this study through a thorough review of published findings, emphasized the presence of antibiotics in animal-derived products and the phenomenon of multidrug resistance in environmental samples. This therefore calls for strengthening of regulations that direct antibiotic manufacture, distribution, dispensing, and prescription, hence fostering antibiotic stewardship. Joint collaboration across the world with international bodies is needed to assist the developing countries to implement good surveillance of antibiotic use and antibiotic resistance.
670 citations
Cites background from "Agar and broth dilution methods to ..."
...It can be determined both by micro broth dilution in microplates [115], and agar dilution [116]....
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References
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01 Jan 2001
TL;DR: The supplemental information presented in this document is intended for use with the antimicrobial susceptibility testing procedures published in the following Clinical and Laboratory Standards Institute (CLSI)–approved standards.
Abstract: The supplemental information presented in this document is intended for use with the antimicrobial susceptibility testing procedures published in the following Clinical and Laboratory Standards Institute (CLSI)–approved standards: M02-A12—Performance Standards for Antimicrobial Disk Susceptibility Tests; Approved Standard—Twelfth Edition; M07-A10—Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically; Approved Standard—Tenth Edition; and M11-A8—Methods for Antimicrobial Susceptibility Testing of Anaerobic Bacteria; Approved Standard— Eighth Edition. The standards contain information about both disk (M02) and dilution (M07 and M11) test procedures for aerobic and anaerobic bacteria. Clinicians depend heavily on information from the microbiology laboratory for treatment of their seriously ill patients. The clinical importance of antimicrobial susceptibility test results demands that these tests be performed under optimal conditions and that laboratories have the capability to provide results for the newest antimicrobial agents. The tabular information presented here represents the most current information for drug selection, interpretation, and QC using the procedures standardized in the most current editions of M02, M07, and M11. Users should replace the tables published earlier with these new tables. (Changes in the tables since the previous edition appear in boldface type.) Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Susceptibility Testing. 26th ed. CLSI supplement M100S (ISBN 1-56238-923-8 [Print]; ISBN 1-56238924-6 [Electronic]). Clinical and Laboratory Standards Institute, 950 West Valley Road, Suite 2500, Wayne, Pennsylvania 19087 USA, 2016. The data in the interpretive tables in this supplement are valid only if the methodologies in M02-A12—Performance Standards for Antimicrobial Disk Susceptibility Tests; Approved Standard—Twelfth Edition; M07-A10—Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically; Approved Standard—Tenth Edition; and M11-A8—Methods for Antimicrobial Susceptibility Testing of Anaerobic Bacteria; Approved Standard— Eighth Edition are followed.
17,824 citations
TL;DR: Standardized methods for determining minimum inhibitory concentrations and MBCs are described and like all standardized procedures, the method must be adhered to and may not be adapted by the user.
Abstract: Minimum inhibitory concentrations (MICs) are defined as the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation, and minimum bactericidal concentrations (MBCs) as the lowest concentration of antimicrobial that will prevent the growth of an organism after subculture on to antibiotic-free media. MICs are used by diagnostic laboratories mainly to confirm resistance, but most often as a research tool to determine the in vitro activity of new antimicrobials, and data from such studies have been used to determine MIC breakpoints. MBC determinations are undertaken less frequently and their major use has been reserved for isolates from the blood of patients with endocarditis. Standardized methods for determining MICs and MBCs are described in this paper. Like all standardized procedures, the method must be adhered to and may not be adapted by the user. The method gives information on the storage of standard antibiotic powder, preparation of stock antibiotic solutions, media, preparation of inocula, incubation conditions, and reading and interpretation of results. Tables giving expected MIC ranges for control NCTC and ATCC strains are also supplied.
3,668 citations
"Agar and broth dilution methods to ..." refers methods in this paper
...A list of solvents for frequently used antibiotics is found in ref...
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TL;DR: The role of cationic host-defense peptides in modulating the innate immune response and boosting infection-resolving immunity while dampening potentially harmful pro-inflammatory (septic) responses gives these peptides the potential to become an entirely new therapeutic approach against bacterial infections.
Abstract: Short cationic amphiphilic peptides with antimicrobial and/or immunomodulatory activities are present in virtually every life form, as an important component of (innate) immune defenses. These host-defense peptides provide a template for two separate classes of antimicrobial drugs. Direct-acting antimicrobial host-defense peptides can be rapid-acting and potent, and possess an unusually broad spectrum of activity; consequently, they have prospects as new antibiotics, although clinical trials to date have shown efficacy only as topical agents. But for these compounds to fulfill their therapeutic promise and overcome clinical setbacks, further work is needed to understand their mechanisms of action and reduce the potential for unwanted toxicity, to make them more resistant to protease degradation and improve serum half-life, as well as to devise means of manufacturing them on a large scale in a consistent and cost-effective manner. In contrast, the role of cationic host-defense peptides in modulating the innate immune response and boosting infection-resolving immunity while dampening potentially harmful pro-inflammatory (septic) responses gives these peptides the potential to become an entirely new therapeutic approach against bacterial infections.
3,556 citations
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...Please note however that cation-adjusted MHB should not be used when testing the activity of cationic antimicrobial peptides, as the presence of Ca 2+ and Mg 2+ ions causes a substantial inhibition of the cationic peptides' activit...
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01 Jan 1971
TL;DR: A working party of people well known internationally in the field of antibiotic sensitivity testing was set up under World Health Organization sponsorship in 1961 to investigate the possibility of introducing standard techniques which might become universal reference methods.
Abstract: A working party of people well known internationally in the field of was set up under World Health Organization sponsorship in 1961 to study the reproducibility of antibiotic sensitivity testing. Their aim was to investigate the possibility of introducing standard techniques which might become universal reference methods. The work involved 16 laboratories. Each was provided with the same 16 organisms, supplies of standard media and antibiotics and precise instructions for their use. The Other CABI sites
1,375 citations
TL;DR: Although bacteriostatic/bactericidal data may provide valuable information on the potential action of antibacterial agents in vitro, it is necessary to combine this information with pharmacokinetic and pharmacodynamic data to provide more meaningful prediction of efficacy in vivo.
Abstract: The distinction between bactericidal and bacteriostatic agents appears to be clear according to the in vitro definition, but this only applies under strict laboratory conditions and is inconsistent for a particular agent against all bacteria. The distinction is more arbitrary when agents are categorized in clinical situations. The supposed superiority of bactericidal agents over bacteriostatic agents is of little relevance when treating the vast majority of infections with gram-positive bacteria, particularly in patients with uncomplicated infections and noncompromised immune systems. Bacteriostatic agents (e.g., chloramphenicol, clindamycin, and linezolid) have been effectively used for treatment of endocarditis, meningitis, and osteomyelitis--indications that are often considered to require bactericidal activity. Although bacteriostatic/bactericidal data may provide valuable information on the potential action of antibacterial agents in vitro, it is necessary to combine this information with pharmacokinetic and pharmacodynamic data to provide more meaningful prediction of efficacy in vivo. The ultimate guide to treatment of any infection must be clinical outcome.
924 citations
"Agar and broth dilution methods to ..." refers background in this paper
...Factors that affect the response to therapy are far more complex and include host defense mechanisms, underlying diseases of the patient, the site of infection, and the pharmacokinetic and pharmacodynamic properties of the drug...
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