The Amount of Agar in Antimicrobic Disk Susceptibility Test Plates

Barry, Arthur L.; Fay, Gunnar D.

doi:10.1093/ajcp/59.2.196

Cited by 8 publications

(7 citation statements)

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“…Although the quality of discs and media is mostly in the hands of the manufacturers, the final responsibility for the correctness of AST results rests with the laboratory. The properties of MH agar, such as pH [12], agar depth [13] and the content of divalent cations [14e17], and thymidine [18,19], will affect inhibition zone formation. In this study, we aimed to identify all manufacturers of dehydrated MH agar and evaluate the performance against defined type culture collection strains (QC strains) with EUCAST quality control (QC) criteria, in the form of defined target values and acceptable ranges.…”

Section: Introductionmentioning

confidence: 99%

EUCAST evaluation of 21 brands of Mueller–Hinton dehydrated media for disc diffusion testing

Åhman

Matuschek

Kahlmeter

2020

Clinical Microbiology and Infection

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a b s t r a c tObjectives: MuellereHinton (MH) agar is recommended by EUCAST and CLSI for disc diffusion antimicrobial susceptibility testing. Using EUCAST methodology, we evaluated the performance of 21 internationally available brands of dehydrated MH agar from 17 manufacturers. Methods: MH plates were prepared in-house and evaluated against four quality control (QC) strains tested in triplicate, using EUCAST disc diffusion methodology. This resulted in 30 disceQC strain combinations and 90 readings per MH brand. All brands were tested blindly and in parallel. Results were evaluated against targets and ranges in the EUCAST QC tables. The agar depth, pH and concentration of five cations were measured for all brands. Results: Six brands of MH agar (Bio-Rad, Biolife, Oxoid, Sigma MH 2, BD BBL MH II and CRITERION) demonstrated excellent performance, with !99% of zone diameter readings within QC ranges and !70% on target ±1 mm. The poorest performance was seen for Biolab and Merck MH, with 10% (9/90) and 23% (21/90) of readings outside the QC ranges, respectively. Of all readings, 4.9% (93/1890) were out of range, mainly related to trimethoprim sulfamethoxazole (n ¼ 25), aminoglycosides (n ¼ 25) and fluoroquinolones (n ¼ 15). The cation content differed considerably between the agars, and for four brands pH values were outside the acceptable range 7.2e7.4. Discussions: This study evaluated the performance and content of 21 brands of MH dehydrated media. Six brands showed excellent performance with all investigated antimicrobial classes. Others exhibited problems with one or more classes of agents. This could partly be explained by differences in concentration of specific chemical components and pH. Clinical Microbiology and Infection xxx (xxxx) xxx Please cite this article as: Åhman J et al., EUCAST evaluation of 21 brands of MuellereHinton dehydrated media for disc diffusion testing, Clinical Microbiology and Infection, https://doi.

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Section: Introductionmentioning

confidence: 99%

EUCAST evaluation of 21 brands of Mueller–Hinton dehydrated media for disc diffusion testing

Åhman

Matuschek

Kahlmeter

2020

Clinical Microbiology and Infection

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“…The growth of microbes in the vicinity of the disks was inhibited by the antimicrobial properties of the test materials, resulting in clearly visible zones without microbial growth. Finally, the ability to kill microorganisms of the test agents was assessed by calculating the size of the zones where growth was inhibited, expressed in millimeters 31,32 …”

Section: Methodsmentioning

confidence: 99%

Exploring therapeutic potential of Woodfordia fruticosa (L.) Kurz leaf and bark focusing on antioxidant, antithrombotic, antimicrobial, anti‐inflammatory, analgesic, and antidiarrheal properties

Rahman,

Soma,

Sultana

et al. 2023

Health Science Reports

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Background and AimsThe study aimed to evaluate the pharmacological properties of methanolic extracts of leaves and barks of Woodfordia fruticosa (L.) Kurz (family: Lythraceae) focusing on antioxidant, thrombolytic, anti‐inflammatory, antibacterial, analgesic, and antidiarrheal effects.Methods1,1‐Diphenyl‐2‐picrylhydrazyl (DPPH) free radical scavenging assay, clot lysis, disc diffusion, and membrane stabilizing methods were employed to assess in vitro antioxidant, thrombolytic, antibacterial, and anti‐inflammatory properties of the leaf and bark methanolic extracts (ME) of W. fruticosa and different organic solvents, that is, petroleum ether (PE), dichloromethane (DCM), chloroform (CL), and aqueous (AQ) fractions. In addition, in vivo central and peripheral analgesic and antidiarrheal activities of both crude extracts were evaluated at two doses (200 and 400 mg/kg of body weight [bw]).ResultsAll the extracts and fractions showed promising antioxidant properties by scavenging DDPH free radicals with IC50 of 6.11–20.79 μg/mL. AQ fraction (41.24%) of leaves and ME (44.90%) of bark exerted notable in vitro thrombolytic activity. The CL fraction of leaves and AQ fraction of the bark showed 43.16% and 45.37% inhibition of RBC hemolysis, respectively, compared to the inhibition of RBC hemolysis by aspirin in a hypotonic‐induced membrane stabilizing assay. Besides, both extracts were observed to provide significant (p < 0.001) central and peripheral analgesic responses at both doses of 200 and 400 mg/kg bw. Furthermore, both doses of bark extract (p < 0.001) and the 400 mg/kg bw of leaf extract (p < 0.05) were observed to possess statistically significant antidiarrheal activity. Additionally, in an in vivo acute toxicity investigation, both extracts had a median lethal dose (LD50) greater than 5000 mg/kg bw, indicating their safety level.ConclusionThe current study proves the ethnomedicinal uses of W. fruticosa; however, further studies are required for phytochemical screening to isolate the responsible bioactive compounds and discover the lead molecules from the plant species.

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“…The zones of inhibition are measured in millimetres. The optimal depth of agar is about 4 mm (Barry & Fay 1973).…”

Section: Methods U S I N G S O L I D Mediamentioning

confidence: 99%

Techniques used for the determination of antimicrobial resistance and sensitivity in bacteria

Piddock

1990

Journal of Applied Bacteriology

122

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The Amount of Agar in Antimicrobic Disk Susceptibility Test Plates

Cited by 8 publications

References 0 publications

EUCAST evaluation of 21 brands of Mueller–Hinton dehydrated media for disc diffusion testing

EUCAST evaluation of 21 brands of Mueller–Hinton dehydrated media for disc diffusion testing

Exploring therapeutic potential of Woodfordia fruticosa (L.) Kurz leaf and bark focusing on antioxidant, antithrombotic, antimicrobial, anti‐inflammatory, analgesic, and antidiarrheal properties

Techniques used for the determination of antimicrobial resistance and sensitivity in bacteria

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