Which bacteria are described as pus-forming and form grape-like clusters?

• A. Streptococci
• B. Diplococci
• C. Cocci
• D. Staphylococci

Answer: (D)

Pus-forming bacteria that arrange themselves in grape-like clusters are Staphylococci. These Gram-positive cocci divide in multiple planes, so they group together into irregular clusters that look like bunches of grapes under the microscope. Their pus-forming tendency, or pyogenic nature, comes from virulence factors such as enzymes and toxins that promote tissue damage and recruit white blood cells, leading to abscesses and boils—S. aureus being a common example. This cluster pattern helps distinguish them from other cocci: streptococci grow in chains, while diplococci appear as pairs. So the combination of grape-like clusters and pus production points to Staphylococci.