July 16th – Bartonella henselae, formerly Rochalimæa, is a proteobacterium that can cause bacteremia, endocarditis, bacillary angiomatosis, and peliosis hepatis. It is also the causative agent of cat-scratch disease (bartonellosis) which, as the name suggests, occurs after a cat bite or scratch. The disease is characterized by lymphadenopathy (swelling of the lymph nodes) and fever. Peliosis hepatis caused by B. henselae can occur alone or develop with cutaneous bacillary angiomatosis or bacteremia. Patients with peliosis hepatis present with gastrointestinal symptoms, fever, chills, and an enlarged liver and spleen containing blood-filled cavities. This systemic disease is mostly seen in patients infected with HIV and other immunocompromised individuals. B. henselae is a member of the Bartonella genus, one of the most common types of bacteria in the world. It infects the host cell by sticking to it using trimeric autotransporter adhesins. The presence of bacteria can be detected by Warthin-Starry stain, or by a similar silver stain technique performed on infected tissue.