Escherichia coli and Klebsiella pneumoniae are two good quality control choices for the indole test.

Escherichia coli and Klebsiella pneumoniae are two good quality control choices for the indole test. E. coli is indole positive, while K. pneumoniae is indole negative. A positive reaction is noted when there is a red layer at the top of the tube after the addition of Kovács reagent, while the negative result is a lack of color change in the top of the tube after the addition of Kovács reagent.

Which one of the following combinations of organisms would be appropriate positive and negative controls to verify the specific test functions listed?