Bacitracin Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Bacitracin and links to relevant pages within the course.
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| Group A Strep A Disk/SXT In follow up to the previous question, the upper image again illustrates the colonies recovered from the blood culture bottle. The colonies are small, transluscent, gray-yellow, and surrounded by a wide zone of beta hemolysis. The size of the colonies compared to the zones of hemolysis suggests a group A streptococcus. The susceptibility to bacitracin (zone of inhibition around the "A" disk in the lower image) is virtually diagnostic of a group A streptococcus. The absence of a zone of inhibition around the SXT disk indicates resitance to sulfamethoxazole/ trimethoprim. SXT resistance is also shared by group B streptococci, which are, however, resistant to bacitracin. The resistance to SXT is used for the primary recovery of groups A and B streptococci from specimens with mixed culture. Their resistance allows them to selectively grow out from contaminating bacteria that are inhibited by this antibiotic. | View Page |
| Beta hemolytic colonies grew from the blood culture bottle after 18 hours incubation (see image). Which of following tests would be helpful in making a preliminary identification? (Choose all that apply) | View Page |
| Thus, in follow-up to the previous discussion, the reaction shown in the image establishes the identification of a group A, beta hemolytic streptococcus. | View Page |
| Group A beta-hemolytic streptococci are best characterized by which of the following: | View Page |
| Which of the following is a presumptive test for the identification of Lancefield group A Streptococcus: | View Page |
| Which two of the following tests are helpful for documenting previous Streptococcal throat and skin infections: | View Page |
| Bacitracin susceptibility is useful for which two of the following: | View Page |
| Which one of the following organisms is sensitive to bacitracin: | View Page |
