A catalase test was performed from a sheep blood agar plate on a colony of streptococci, and bubbling was observed. Which of the following statements explains this discrepancy?
a. Catalase is the inappropriate test to use on colonies of streptococci; therefore the re-sults are invalid.
b. The colony may have been contaminated with sheep red blood cells, causing a false-positive result.
c. The colony was most likely enterococci, not streptococci.
d. No discrepancy is present. Streptococcus is a catalase-positive colony.
B
Sheep red blood cells produce catalase; therefore, if some of the media was incorporated into the colony, a false-positive result would occur, because streptococci are catalase-negative colonies.
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