Which organism is a non-spore-forming, gram-positive anaerobic bacillus?

Which organism is a non-spore-forming, gram-positive anaerobic bacillus?

• A. Propionibacterium
• B. Clostridium
• C. Fusobacterium
• D. Veillonella

Answer: (A)

Distinguishing features here are Gram reaction, spore formation, and oxygen requirements. Propionibacterium is a Gram-positive rod that does not form spores and grows under anaerobic conditions, matching all three descriptors. The other organisms don’t fit: Clostridium is Gram-positive and anaerobic but forms spores; Fusobacterium is anaerobic and rod-shaped but Gram-negative; Veillonella is anaerobic and Gram-negative cocci. Thus, Propionibacterium best fits the description of a non-spore-forming, Gram-positive anaerobic bacillus.

Distinguishing features here are Gram reaction, spore formation, and oxygen requirements. Propionibacterium is a Gram-positive rod that does not form spores and grows under anaerobic conditions, matching all three descriptors. The other organisms don’t fit: Clostridium is Gram-positive and anaerobic but forms spores; Fusobacterium is anaerobic and rod-shaped but Gram-negative; Veillonella is anaerobic and Gram-negative cocci. Thus, Propionibacterium best fits the description of a non-spore-forming, Gram-positive anaerobic bacillus.