This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
School of fish appearance is characteristic of - 
Select and explain. 
A. Bordetella pertussis, B. Yersinia enterocolitica, C. Haemophillus ducreyi, D. Legionella
C: Haemophillus ducreyi
Answer: C: Haemophillus ducreyi 
Explanation: Ans. is 'c' i.e., Haemophillus ducreyi* H duceryi is Gram negative but often may appear Gram positive and frequently shows bipolar staining.* The bacilli may be arranged in small groups or whorls or in parallel chains giving a "school offish" or "rail road track appearance".