ID#: 10793
This 1972 image depicted two Mueller-Hinton agar culture plates that had been used in an antibiotic susceptibility test (AST). The pH of the left plate was labeled as 7.2, while the plate at right was labeled at a value of 8.0, which was slightly more alkaline than the left plate. Known as the Kirby-Bauer method, each of the small, labeled discs, or wafers, contained an antimicrobial agent. The light halos surrounding each disc, also known as reaction zones, represented regions in which the bacteria on the agar’s surface did not thrive, due to their sensitivity to the antibiotic that had been soaked into these respective discs. Note the subtle differences in bacterial growth, due to the differing pH values. These tests, which measure the presence or absence of a reaction zone, also take into account the pH of the medium, the concentration of the inoculum, and a number of other factors.
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Content Provider(s): CDC/ Gilda L. Jones
Creation Date: 1972
Photo Credit:
CDC Organization
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Copyright Restrictions: None - This image is in the public domain and thus free of any copyright restrictions.