A yellow, nonfermentative gram-negative bacillus isolated from nebulizers in an environmental sampling study most likely belongs to which genus?

A yellow, nonfermentative gram-negative bacillus isolated from nebulizers in an environmental sampling study most likely belongs to which genus?

• A. Pseudomonas
• B. Moraxella
• C. Chryseobacterium
• D. Alcaligenes

Answer: (C)

Look for a visual clue in the pigment plus the environmental source. Chryseobacterium species are known for producing a yellow pigment, giving yellow-orange colonies, and they are nonfermentative Gram-negative bacilli that are commonly found in water environments, including hospital water systems and devices such as nebulizers. In an environmental sampling study of nebulizers, this combination of yellow pigmentation and nonfermenting G- rods is a classic hint pointing to Chryseobacterium rather than other nonfermenters. Why this fits best: the yellow pigment is a hallmark feature of Chryseobacterium due to flexirubin-type pigments, and their association with water-related sources in healthcare settings is well documented, making them a likely isolate from nebulizers. Why other options are less fitting: Moraxella are typically Gram-negative diplococci rather than bacilli. Alcaligenes can be nonfermentative rods but are not characteristically yellow-pigmented in the same diagnostic way and aren’t as strongly linked to that pigment clue. Pseudomonas can be nonfermentative and environmental, but they are usually associated with distinctive pigments like blue-green (pyocyanin) or yellow-green; the classic yellow pigment specifically points toward Chryseobacterium in this context.

Look for a visual clue in the pigment plus the environmental source. Chryseobacterium species are known for producing a yellow pigment, giving yellow-orange colonies, and they are nonfermentative Gram-negative bacilli that are commonly found in water environments, including hospital water systems and devices such as nebulizers. In an environmental sampling study of nebulizers, this combination of yellow pigmentation and nonfermenting G- rods is a classic hint pointing to Chryseobacterium rather than other nonfermenters.

Why this fits best: the yellow pigment is a hallmark feature of Chryseobacterium due to flexirubin-type pigments, and their association with water-related sources in healthcare settings is well documented, making them a likely isolate from nebulizers.

Why other options are less fitting: Moraxella are typically Gram-negative diplococci rather than bacilli. Alcaligenes can be nonfermentative rods but are not characteristically yellow-pigmented in the same diagnostic way and aren’t as strongly linked to that pigment clue. Pseudomonas can be nonfermentative and environmental, but they are usually associated with distinctive pigments like blue-green (pyocyanin) or yellow-green; the classic yellow pigment specifically points toward Chryseobacterium in this context.