Tetrad Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Tetrad and links to relevant pages within the course.
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| PYR Differential As mentioned before, the spot PYR test is commonly performed to separate Enterococcus species (positive reaction) from the Group D streptococci (S. bovis, S. equinus), which are negative.It should be remembered that Streptococcus pyogenes (group A) also produces PYR; therefore, additional characteristics such as beta hemolysis are important.Some species of Aerococcus and Gemella are also PYR-positive; however, they can be suspected if large cocci in tetrads or clusters are observed on gram stain.These species are rare isolates in most clinical practices. | View Page |
| A gram stain of the serous exudate is shown in the photograph. The appropriate report would read: | View Page |
| Bacterial arrangements that can be seen on a smear include: | View Page |
| Tetrad Cell Arrangement Examples of Gram positive bacteria appearing in tetrads are seen in this slide. Sometimes bacteria in tetrad may not be as clear cut as this drawing indicates, and appear as clusters. N. gonorrhea colonies may appear as tetrads especially if the smear is made from very young colonies.
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