Bacterial arrangements: the cocci that typically form irregular, grape-like clusters (a “bunch”) are called:

Introduction / Context:
Arrangement of cocci is a rapid visual clue in Gram-stained smears. Recognizing clusters versus chains versus pairs directs differential diagnosis and informs likely genera involved.

Given Data / Assumptions:

• “Bunch” and “irregular pattern” implies grape-like clusters.
• Pairs correspond to diplococci; chains correspond to streptococci; packets of four are tetrads.
• Staphylococci are known for irregular clusters due to division in multiple planes with post-division adhesion.

Concept / Approach:
Staphylococci classically appear as clusters, resembling bunches of grapes, due to division in multiple planes and characteristic adhesion. This appearance differentiates them from streptococci (chains) and diplococci (pairs).

Step-by-Step Solution:

Verification / Alternative check:
Clinical microbiology atlases show Staphylococcus aureus in clusters, aiding quick recognition in wound and blood culture smears.

Why Other Options Are Wrong:
Diplococci: Pairs, not clusters. Tetracocci: Groups of four in a packet. Streptococci: Chains, not irregular bunches.

Common Pitfalls:
Misinterpreting dense fields of diplococci as clusters; careful focus reveals typical arrangements.

Final Answer:
Staphylococci