Which bacillus is associated with epithelioid histiocytes surrounding small cutaneous nerves?

Mycobacterium leprae is the bacillus associated with epithelioid histiocytes surrounding small cutaneous nerves. This bacterium is the causative agent of leprosy, also known as Hansen's disease. In leprosy, the immune response to the infection characteristically involves the formation of granulomas composed of epithelioid histiocytes. These granulomas can specifically encapsulate small nerve fibers, leading to the characteristic nerve damage and skin lesions seen in leprosy patients. The presence of epithelioid histiocytes is a hallmark of the immune response to this pathogen, highlighting how the body attempts to contain the infection.

In contrast, Mycobacterium tuberculosis primarily affects the lungs and induces a different type of immune response, typically involving caseating granulomas rather than those surrounding nerves. Salmonella typhi is associated with typhoid fever and does not lead to the formation of epithelioid histiocytes surrounding nerves. Similarly, Staphylococcus aureus is a common cause of skin infections and abscesses but does not involve the specific granulomatous response associated with nerve involvement. Thus, the unique association of Mycobacterium leprae with epithelioid histiocytes around cutaneous