A gram-positive coccus that is catalase positive, nonmotile, lysostaphin resistant, and modified oxidase positive is best identified as a member of the genus

A gram-positive coccus that is catalase positive, nonmotile, lysostaphin resistant, and modified oxidase positive is best identified as a member of the genus

• A. Lactococcus
• B. Micrococcus
• C. Staphylococcus
• D. Pediococcus

Answer: (B)

Distinguishing Gram-positive cocci that are catalase positive relies on a sequence of tests to separate closely related genera. The combination described—catalase positive, nonmotile, lysostaphin resistant, and oxidase positive (modified oxidase positive)—points away from Staphylococcus, which is typically oxidase negative and lysostaphin sensitive, and away from lactic acid cocci like Lactococcus and Pediococcus, which are catalase negative. Micrococcus fits all the traits: it is a catalase-positive, nonmotile Gram-positive coccus that is resistant to lysostaphin and shows a positive oxidase (modified oxidase) reaction. The oxidation-reduction profile and lysostaphin resistance help confirm this genus, especially when considered alongside the common presentation of Micrococcus as pigmented, often tetrad-forming cocci. Therefore, the best identification for this profile is Micrococcus.

Distinguishing Gram-positive cocci that are catalase positive relies on a sequence of tests to separate closely related genera. The combination described—catalase positive, nonmotile, lysostaphin resistant, and oxidase positive (modified oxidase positive)—points away from Staphylococcus, which is typically oxidase negative and lysostaphin sensitive, and away from lactic acid cocci like Lactococcus and Pediococcus, which are catalase negative. Micrococcus fits all the traits: it is a catalase-positive, nonmotile Gram-positive coccus that is resistant to lysostaphin and shows a positive oxidase (modified oxidase) reaction. The oxidation-reduction profile and lysostaphin resistance help confirm this genus, especially when considered alongside the common presentation of Micrococcus as pigmented, often tetrad-forming cocci. Therefore, the best identification for this profile is Micrococcus.