Safety pin appearance is shown by?

Hemophilus ducreyi is a sho ovoid bacillus with a tendency to occur in the end to end pairs or sho chains. It is Gram-negative but may often appear Gram-positive and frequently shows Bipolar staining. The bacilli may be arranged in small groups or whole or in parallel chains giving a School of Fish or Railroad track appearance Other examples: Yersinia pestis REF:Ananthanarayan & panickers Textbook of Microbiology 9th edition page no331