Rickettsia
Rickettsia is a genus of non-motile, Gram-negative, non-sporeforming, highly pleomorphic bacteria that can present as cocci, rods or thread-like. Being obligate intracellular parasites, the
Rickettsia survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells. Because of this,
Rickettsia cannot live in artificial nutrient environments and is grown either in tissue or embryo cultures. In the past it was positioned somewhere between viruses and true bacteria. However unlike
Chlamydia,
Mycoplasma, and
Ureaplasma, Rickettsial organisms possess true cell walls similar to other Gram-negative bacteria. The majority of
Rickettsia bacteria are susceptible to antibiotics of the tetracycline group. Despite the similar name,
Rickettsia bacteria do not cause rickets, which is a result of vitamin D deficiency.
Rickettsia species are carried by many chiggers, ticks, fleas, and lice, and cause diseases in humans such as typhus, rickettsialpox, Boutonneuse fever, African tick bite fever, Rocky Mountain spotted fever, Flinders Island spotted fever and Queensland tick typhus.