A Gram stain shows Gram-positive cocci in grape-like clusters. Which genus is commonly associated with this appearance?

A Gram stain shows Gram-positive cocci in grape-like clusters. Which genus is commonly associated with this appearance?

• A. Enterococcus
• B. Micrococcus
• C. Streptococcus
• D. Staphylococcus

Answer: (D)

The key idea here is how Gram-positive cocci appear arranged on a smear. When cocci gather in irregular, grape-like clusters, that pattern is classic for Staphylococcus. This clustered arrangement comes from the way these cells divide in multiple planes and stay together rather than lining up in chains. In contrast, Streptococcus and Enterococcus typically form chains or pairs, because they divide in a single plane. Micrococcus often forms tetrads (groups of four) or scattered single cells, not grape-like clusters. So the genus most commonly associated with grape-like clusters is Staphylococcus, with Staphylococcus aureus being a well-known example.

The key idea here is how Gram-positive cocci appear arranged on a smear. When cocci gather in irregular, grape-like clusters, that pattern is classic for Staphylococcus. This clustered arrangement comes from the way these cells divide in multiple planes and stay together rather than lining up in chains. In contrast, Streptococcus and Enterococcus typically form chains or pairs, because they divide in a single plane. Micrococcus often forms tetrads (groups of four) or scattered single cells, not grape-like clusters. So the genus most commonly associated with grape-like clusters is Staphylococcus, with Staphylococcus aureus being a well-known example.