Which statement about Pasteurella multocida is true?

• A. Most common human infections occur in soft tissues, bones, and joints.
• B. Humans harbor the organism as part of their normal biota.
• C. It grows well on MacConkey agar.
• D. Isolates are typically penicillin resistant.

Answer: (A)

Pasteurella multocida is most classically encountered as a cause of rapid soft tissue infection after animal bites, especially from cats and dogs, and it can involve deeper structures such as bones and joints. It is not a normal human inhabitant, so humans don’t carry it as part of their native biota. In the lab, it is a gram-negative coccobacillus that grows well on enriched media like blood or chocolate agar but tends to grow poorly on MacConkey agar, helping differentiate it from many enteric bacteria. Most isolates are susceptible to penicillin, so penicillin resistance is not expected. These points together explain why the statement about infections in soft tissues, bones, and joints is the true one.