Rickettsias

Rickettsias

	Tabular Form of Bacterial Classification From David Bergey's Manual Members of this part are rod shaped, Gram negative coccoid and often pleomorphic organisms with typical bacterial cell walls, nonflagellate and multiply only inside the host ceIl. They may be cultivated in the living tissues such as embryonated chicken eggs or vertebrate cell cultures. Division is by binary fission.
All are parasitic or mutualistic and may cause diseases man and other vertebrate and invertebrate hosts. The group includes two orders with the order Rickettsiales having three families.The family Rickettsiaceae, includes parasites that are intracellular or intimately associated with the tissue cells other than erythrocytes or with certain organs in the arthropods generally transmitted by the arthrorod vectors. The family bartonellaceae includes parasites which are intracellular or facultatively extracellular, found normally in erythrocytes of vertebrates. Cells are small, rod shaped, bacteria like and transmitted by arthropods. These can be grown outside the living cells.
The family Anaplasmataceae has very small virus like particles which occur in erythrocytes of vertebrates and transmitted by arthropods. The second order, Chlamydiales includes organisms which are coccoid, obligately intracellular parasites which show a change in size and infectivity during multiplication. It includes one family Chalmydiaceae with only one genus Chlamydia