Which test result best helps differentiate Vibrio vulnificus from other enteric pathogens using susceptibility testing?

Which test result best helps differentiate Vibrio vulnificus from other enteric pathogens using susceptibility testing?

• A. Oxidase positivity
• B. O/129 susceptibility
• C. Gram-negative morphology
• D. Growth at high salt concentrations

Answer: (C)

The main idea is using a practical lab characteristic to separate Vibrio vulnificus from other enteric bacteria during susceptibility testing. Vibrio vulnificus is a Gram-negative organism with a distinctive curved-rod (vibrio) morphology. That Gram-negative cell wall design places it in a different bacterial group from Gram-positive enteric pathogens, which influences how its susceptibility pattern is interpreted and which antibiotics are considered appropriate. Among the features listed, the Gram-negative appearance directly points to the kind of susceptibility profile you’d expect for this organism and helps distinguish it from non–Gram-negative pathogens encountered in enteric infections. Other options describe properties that are helpful in identification but are not as universally deterministic in the context of susceptibility testing. Oxidase positivity is common among many Gram-negative rods, so it doesn’t uniquely identify Vibrio. Growth in high salt is a characteristic of Vibrios but is not a susceptibility test result. The O/129 susceptibility test is a classic differential for Vibrio species, but in this question the most broadly applicable distinguishing feature being emphasized is the Gram-negative morphology.

The main idea is using a practical lab characteristic to separate Vibrio vulnificus from other enteric bacteria during susceptibility testing. Vibrio vulnificus is a Gram-negative organism with a distinctive curved-rod (vibrio) morphology. That Gram-negative cell wall design places it in a different bacterial group from Gram-positive enteric pathogens, which influences how its susceptibility pattern is interpreted and which antibiotics are considered appropriate. Among the features listed, the Gram-negative appearance directly points to the kind of susceptibility profile you’d expect for this organism and helps distinguish it from non–Gram-negative pathogens encountered in enteric infections.

Other options describe properties that are helpful in identification but are not as universally deterministic in the context of susceptibility testing. Oxidase positivity is common among many Gram-negative rods, so it doesn’t uniquely identify Vibrio. Growth in high salt is a characteristic of Vibrios but is not a susceptibility test result. The O/129 susceptibility test is a classic differential for Vibrio species, but in this question the most broadly applicable distinguishing feature being emphasized is the Gram-negative morphology.