This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
A veterinary doctor had pyrexia of unknown origin. His blood culture in special laboratory media was positive for gram-negative sho bacilli which was oxidase positive. Which one of the following is the likely organism grown in culture ? 
Select and explain. 
A. Pasteurella spp, B. Francisella spp, C. Baonella spp, D. Baonella spp
D: Baonella spp
Answer: D: Baonella spp 
Explanation: Ans. is 'd' i.e., Brucella Spp . The clues in this question are : - Gram negative - Oxidase postive - Organism can cause pyrexia of unknown origin (PUO) - Infection is common among veterinarians. . Brucellae have all these features. - Other options can be excluded by morphological features Organism Morhology . Brucella Cocci, cocobacilli or sho bacilli - Greenwood 16th/e p. 322 . Baonella spp. Small coccobacilii - Greenwood 16th/e p. 326 . Francisella spp. Small coccobacilli - Greenwood I 6th/e p. 335 . Pasteurella spp. Coccobacilli - Greenwood 16th/e p. 326 Amongst the given options only brucella can appear as sho bacilli, all others are coccobacilli.