An Organism Suspected of Being One of the Vibrio Spp

An organism suspected of being one of the Vibrio spp.grew on MacConkey agar.To determine whether it was a vibrio cell or in the Enterobacteriaceae family,an oxidase test was performed on the colony.The results of the oxidase test,however,were negative.Which one of the following statements explains this discrepancy?

A) The oxidase test should be performed on TCBS agar,not MacConkey agar.
B) The oxidase test should be performed on a sheep blood agar plate to avoid false-negative results.
C) The pH of the MacConkey agar is most likely elevated to alkaline conditions.
D) No discrepancy is present.All vibrio cells are oxidase-negative.