<prompt> School of fish appearance is characteristic of -Bordetella pertussisYersinia enterocoliticaHaemophillus ducreyiLegionella  <response>: 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. 