Which organism is non-lactose fermenting, oxidase negative, nitrate positive, VP positive, and motile?

Prepare for the CAMLPR Microbiology Test. Utilize flashcards and engaging multiple-choice questions, each equipped with descriptions and explanations. Ready yourself for an excellent performance!

Interpreting this profile hinges on combining several biochemical traits to identify an enteric bacterium. The combination described—non-lactose fermenting, oxidase negative, nitrate positive, Voges-Proskauer positive, and motile—points to Hafnia alvei. Being a non-lactose fermenter helps distinguish it from lactose fermenters on media like MacConkey. Oxidase negative places it with the Enterobacteriaceae family. Nitrate positive shows it can reduce nitrate to nitrite, a common feature in these organisms, and motility confirms it is flagellated. The Voges-Proskauer positive result indicates acetoin production from glucose, a trait Hafnia alvei exhibits and that helps separate it from other non-lactose fermenters that are VP negative.

For comparison, Proteus vulgaris shares several facts—non-lactose fermentation, oxidase negativity, nitrate positivity, and motility—but it is typically Voges-Proskauer negative, so it doesn’t fit the full profile. Providencia rettgeri is also non-lactose fermenting and oxidase negative with nitrate positivity and motility, but again VP is usually negative. Citrobacter freundii often ferments lactose (even if slowly), so it wouldn’t meet the non-lactose criterion.