Which organism is described as GNB eyebrow and non-lactose fermenting?

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Multiple Choice

Which organism is described as GNB eyebrow and non-lactose fermenting?

The main idea here is recognizing a Gram-negative bacillus that does not ferment lactose on standard media, with a particular curved/eyebrow-like appearance seen on smears. Among common enteric bacteria, Salmonella is classically described as a slender, curved Gram-negative rod that can resemble an eyebrow in some stained preps, and it is a non-lactose fermenter. On MacConkey it does not acidify lactose, so colonies stay colorless, and on other differential media like a TSI slant it can produce hydrogen sulfide, which helps confirm its identity. This combination of a curved GNB shape and non-lactose fermentation is a hallmark used in practice to pick Salmonella from among non-lactose fermenters. Vibrio can also be a curved non-lactose fermenter, but it is oxidase positive and often has salt-requiring growth, which helps distinguish it. Haemophilus parainfluenzae is a fastidious coccobacillus that requires specific growth factors and generally doesn’t fit the typical enteric non-lactose-fermenter profile. Proteus penneri is another non-lactose fermenter but is known for swarming on agar and different biochemical traits, not the eyebrow-shaped description.

The main idea here is recognizing a Gram-negative bacillus that does not ferment lactose on standard media, with a particular curved/eyebrow-like appearance seen on smears. Among common enteric bacteria, Salmonella is classically described as a slender, curved Gram-negative rod that can resemble an eyebrow in some stained preps, and it is a non-lactose fermenter. On MacConkey it does not acidify lactose, so colonies stay colorless, and on other differential media like a TSI slant it can produce hydrogen sulfide, which helps confirm its identity. This combination of a curved GNB shape and non-lactose fermentation is a hallmark used in practice to pick Salmonella from among non-lactose fermenters.

Vibrio can also be a curved non-lactose fermenter, but it is oxidase positive and often has salt-requiring growth, which helps distinguish it. Haemophilus parainfluenzae is a fastidious coccobacillus that requires specific growth factors and generally doesn’t fit the typical enteric non-lactose-fermenter profile. Proteus penneri is another non-lactose fermenter but is known for swarming on agar and different biochemical traits, not the eyebrow-shaped description.

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