A farmer presents to the emergency depament with painful inguinal lymphadenopathy and history of fever and flu like symptom. Clinical examination reveals an ulcer in the leg. Which of the following stains ahould be used to detect suspected bipolar stained organisms -

Ans. is `b' i.e., Wayson's stain . Presence of painful lymphadenopathy, ulcer in the leg alongwith constitutional symptoms suggests a probable diagnosis of bubonic plague.Specimen should be immediately examined with Wayson or Giemsa stain which reveals the classical/ typical bipolar staining pattern ( safelty pin) appearance of Yersinia pestis.