Corynebacterium Xerosis Lab Report

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After the incubation period, the agar containing the antibiotic testing was taken out and if the microbe reacted with the antibiotic, a circle or clearing would appear around the disk containing the antibiotic. The diameter of this circle was then measured and compared with a table found on page 95 of the Microbiology Lab Manual to understand the antibiotics resistance, intermediate and sensitive levels, as they differ for each antibiotic. The numbers on the table in the Microbiology Lab Manual represented whether the microbe was resistant, shown in the light blue color on the graph, intermediate, shown in purple, or sensitive to the antibiotic, shown in the periwinkle color. As shown in figure 1 above, indicated with a yellow line, each antibiotic tested on unknown microbe #7 turned out to be sensitive. The diameters of the cleared out areas were vancomycin: 21mm, erythromycin: …show more content…
Initially when unknown microbe #7 was gram stained and observed under the microscope, the color appeared more pink than purple, leading to the conclusion that unknown microbe #7 was gram negative. However, when completing the KOH lysis test, the microbe didn’t become sticky and remained tacky which is how a gram positive KOH test would result. It was decided to double check the KOH lysis test and the second test still yielded the same results as the first, gram positive. The conclusion of unknown microbe #7 being gram negative from the gram stain was an error. This could have been because of the amount of dye on the gram stain, or timing with how long the flooding of the slide should have been done, or human error. But because the KOH lysis test is more reliable than observation of a gram stain under the microscope, it was decided to change the consensus of unknown microbe #7 being gram negative to it being gram

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