Please note, BioLabTests are UNABLE TO TEST ANY VIRUSES including SARS-CoV-2 (COVID-19)
Please note, BioLabTests are UNABLE TO TEST ANY VIRUSES including SARS-CoV-2 (COVID-19)
Kirby-Bauer Disk Diffusion Method2022-05-13T14:46:08+01:00


Disk Diffusion Susceptibility Test

Kirby-Bauer test is widely used to determine the sensitivity or resistance of bacteria to various antimicrobial compounds, and it uses the Mueller Hinton agar.

Mueller-Hinton agar is a non-selective, non-differential medium capable of growing a wide range of non-fastidious organisms. It is considered a ‘loose’ agar, which helps to mediate the rate of diffusion of the antimicrobial more effectively than any other types of media.


Mueller Hinton agar is aseptically inoculated with bacteria via the spread method, and a range of discs impregnated with an antimicrobial are placed on the surface for incubation at 35°C for 24 hours.

After incubation, the plates are observed for a ‘zone of inhibition’; a circular area relating to the level of antimicrobial activity upon the bacteria. Any zone of inhibition present indicates a degree of sensitivity to the antimicrobial; the larger the zone, the more potent the antimicrobial. On the other hand, no zone indicates total bacterial resistance..

The susceptibility of the bacteria can then be measured by taking the diameter of the inhibition zone from the centre of the disc and matching the number to a standard of values, depending on the antimicrobial and concentration.


Whilst this method is primarily used for antibiotic susceptibility, it can be used to test other antimicrobials, such as the effectiveness of detergents and hand sanitisers.

Testing using the Kirby-Bauer method can for example determine whether a microorganism, such as MRSA, is resistant to a specific antimicrobial. This could be useful to support research in finding a suitable detergent for laboratories to help make informed decisions on the applicability of a cleaning agent.

In recent years, there has been a lot of interest in antimicrobials, such as research into the antimicrobial activity of silver nanoparticles with and without the combination of antibiotics.

How BioLabTests can support you

If the Kirby-Bauer Test would be of interest to you or you would like to explore another microbiology testing, please do not hesitate to get in touch with a member of our team on +44 (0) 333 240 8308. Alternatively, you can fill in our contact form for a quote or more information regarding our antimicrobial testing capabilities..

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Antimicrobial Testing with Mueller Hinton Agar

BioLabTests offers a wide range of testing, from environmental, product and antimicrobial testing to hygiene audit support and microbiological research. Some of our services for antimicrobial testing include the Kirby Bauer Test and the Minimum Inhibitory Concentration (MIC) Testing. Here we share further information on the tests, their purpose for real-life applications and of course [...]

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