n.
Any of the rod-shaped bacteria that make up the family Rickettsiaceae (named for Howard Ricketts ).
They are rod-shaped or variably spherical, and most are gram-negative (see gram stain ). Natural parasites of certain arthropods , they can cause serious diseases in humans and other animals, to which they are usually transmitted by a bite from an arthropod carrier. Because certain species can survive considerable drying, rickettsias can also be transmitted when arthropod feces are inhaled or enter the skin through abrasion. Typhus , trench fever, and Rocky Mountain spotted fever are rickettsial infections. The most effective treatment includes timely and prolonged administration of broad-spectrum antibiotics.