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Infectious Disease
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Susanna J. Dunachie, Hanif Esmail, Ruth Corrigan, Maria Dudareva
For the Kirby-Bauer disc diffusion method of AST, a suspension of bacteria is spread on an agar plate and then discs containing antibiotics are added (Figure 3.10). Following incubation, the ability of each antibiotic to inhibit bacterial growth is determined by measuring the zone of inhibition. Sensitivity or resistance is determined by comparing the inhibition zone size against standard criteria in the guidelines.
Natural Products from the Amazon Region as Potential Antimicrobials
Published in Mahendra Rai, Chistiane M. Feitosa, Eco-Friendly Biobased Products Used in Microbial Diseases, 2022
Josiane E. A. Silva, Iasmin L. D. Paranatinga, Elaine C. P. Oliveira, Silvia K. S. Escher, Ananda S. Antonio, Leandro S. Nascimento, Patricia P. Orlandi, Valdir F. Veiga-Júnior
A more common fruit in tropical regions, including Amazonia, is the cashew (Anacardium occidentale - Anacardiaceae). Several pharmacological activities have already been described, such as anti-inflammatory, antidiabetic and antimicrobial. Leaf plant extracts of the Anacardium occidentale L. species have shown to be potentially active against Escherichia coli, Staphylococcus aureus and Candida albicans strains, showing the antimicrobial potential of the cashew extract (Anand et al. 2015; Ajileye et al. 2015). The inhibition halo assay is another very useful method to analyze the potential antimicrobial activity. A paper disk containing an amount of a known antibiotic is put in a microorganism growth media, such as agar (Table 2.2). The zone of inhibition around the antibiotic-containing disk indicates the sensitivity of the bacteria to the antibiotic in the disk. With this assay, unknown substances or complex mixtures, such as extracts, can be evaluated in comparison to known antibiotics.
Understanding the Antibiogram
Published in Firza Alexander Gronthoud, Practical Clinical Microbiology and Infectious Diseases, 2020
Microbiology laboratories determine antimicrobial susceptibility through tests whereby organisms are cultured in the presence of antimicrobial agents (phenotypic tests). Based on the minimum concentration of an antibiotic needed to inhibit growth (also called MIC; measured by microbroth dilution or MIC gradient strips) or based on the zone of inhibition (when using disk diffusion), the result is reported as sensitive, resistant or intermediate sensitive. Intermediate sensitive means that treatment may still be effective if a higher dose is used and if the infection is in a body compartment where the antibiotic has a good tissue penetration, i.e. β-lactams in the urinary tract.
Quality and suitability of antimicrobial discs: theoretical and practical sources of error and variability
Published in Expert Review of Molecular Diagnostics, 2020
The use of antimicrobial discs remains one of the main methods for assessing antibiotic activity. The method, also known as the Kirby–Bauer test, relies on the diffusion of active ingredients from a paper disc into an agar plate that has been inoculated with the microbial sample. As the bacterial growth becomes visible a zone of inhibition appears where the antibiotic has been of sufficient concentration to inhibit growth. In clinical use, usually around six or more antibiotics are tested for a particular infection, and the zone measurements are used as a guide to decide which antibiotic to use. Various organizations (EUCAST in Europe and CLSI in the US) have published breakpoint tables of the zone sizes indicating whether the organism is resistant, intermediate, or susceptible to the antibiotic. Breakpoints roughly correlate with minimum inhibitory concentrations (MIC) though the graphs show a fair amount of scatter [1]. In addition, quality zone ranges have been published to enable the quality of discs to be checked.
Evaluation of paromomycin sulphate permeation using ex vivo human skin model
Published in Pharmaceutical Development and Technology, 2019
Enam A. Khalil, Mahmoud Y. Alkawareek, Ghadeer Othman, Bayan Tbakhi, Amal G. Al-Bakri
Paromomycin analysis was carried out using potency-based microbiological assay based on Kirby-Bauer agar diffusion method as described by the US Pharmacopeia (USP-29 2005) with some modifications. Briefly, an inoculum size of ca. 1 × 107CFU/ml of mid-log culture of Staphylococcus epidermidis (ATCC 12228) was used to prepare a bacterial lawn on Müller-Hinton agar. Blank antibiotic assay discs were loaded with 20 µl standard or test antibiotic solution and then placed on the surface of the inoculated agar plates which were then incubated at 35 °C for 18–24 h. The diameter of each zone of inhibition was measured and the obtained values were used either in the construction of calibration curve or in the determination of the antibiotic concentration in test solutions.
Iodinated curcumin bearing dermal cream augmented drug delivery, antimicrobial and antioxidant activities
Published in Journal of Microencapsulation, 2018
Gagandeep Manchanda, Rupinder Kaur Sodhi, Upendra Kumar Jain, Ramesh Chandra, Jitender Madan
The antibacterial activity of tailored creams was determined using standard cup-plate method (Davis and Stout, 1971). E. coli and S. aureus were used for testing the antibacterial activity of Cur, I2, Cur–I2 powder, Cur cream, Cur–I2 cream and marketed cream in the concentration range of 30–270 µg/ml. Nutrient agar medium and Luria Broth agar medium were used in the assay method for incubating E. coli and S. aureus at the temperature of 37 °C for 48 h. The zone of inhibition in each plate was measured using an antibiotic zone reader (Hindustan Apparatus, Mumbai, India). Each experiment was carried out in triplicate (n = 3).