A positive blood culture vial reveals gram-negative rods. After subculture, the organism grew as
Sheep blood agar: large, gray colonies with beta-hemolysis
MacConkey agar: round, smooth, pink colonies
Phenylethyl alcohol agar: no growth
Rapid testing revealed
Oxidase: no color change
Pigment: none observed
Spot indole: red-pink
The organism is

Question

Quizplus · Accepted Answer

The organism is Escherichia coli (E. coli) because it shows growth on MacConkey agar as pink colonies (indicating lactose fermentation), produces beta-hemolysis on sheep blood agar, does not grow on phenylethyl alcohol agar (which inhibits Gram-negative organisms other than enterics), is oxidase negative (no color change), does not produce pigment, and tests positive for spot indole (red-pink color), which are all characteristics of E. coli.

A Positive Blood Culture Vial Reveals Gram-Negative Rods