Which organism is non-lactose fermenting, oxidase negative, and demonstrates DNAse positivity?

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Multiple Choice

Which organism is non-lactose fermenting, oxidase negative, and demonstrates DNAse positivity?

Non-lactose fermenting, oxidase negative, and DNAse positive describes a specific profile used to identify certain non-fermenting Gram-negative rods. Acinetobacter fits all three: it is a Gram-negative coccobacillus that does not ferment lactose on MacConkey, so colonies remain colorless; it is oxidase negative, helping distinguish it from oxidase-positive organisms like Pseudomonas; and it exhibits extracellular DNase activity, giving a positive DNase test. The other organisms do not meet all three criteria: Haemophilus parainfluenzae is oxidase positive and has different growth factor requirements; Salmonella is lactose non-fermenting and oxidase negative but typically lacks this DNase positivity in routine testing; Stenotrophomonas maltophilia is non-lactose fermenting and oxidase negative but does not share the DNase-positive profile highlighted here.

Non-lactose fermenting, oxidase negative, and DNAse positive describes a specific profile used to identify certain non-fermenting Gram-negative rods. Acinetobacter fits all three: it is a Gram-negative coccobacillus that does not ferment lactose on MacConkey, so colonies remain colorless; it is oxidase negative, helping distinguish it from oxidase-positive organisms like Pseudomonas; and it exhibits extracellular DNase activity, giving a positive DNase test. The other organisms do not meet all three criteria: Haemophilus parainfluenzae is oxidase positive and has different growth factor requirements; Salmonella is lactose non-fermenting and oxidase negative but typically lacks this DNase positivity in routine testing; Stenotrophomonas maltophilia is non-lactose fermenting and oxidase negative but does not share the DNase-positive profile highlighted here.

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