. Author manuscript; available in PMC: 2022 Mar 10.

Published in final edited form as: Zoonoses (Burlingt). 2021 Oct 25;1(1):10. doi: 10.15212/zoonoses-2021-0011

Table 1.

Overview of Obligate Intracellular Bacterium Characteristics and Defined Immune Sensing

Obligate Intracellular Species	Reservoir	Transmission		Primary Host Cell for Replication	Location in Host Cell	Receptor(s) in Recognition	Adaptor Proteins Implicated
Obligate Intracellular Species	Reservoir	Animal Vector	Arthropod Vector	Primary Host Cell for Replication	Location in Host Cell	Receptor(s) in Recognition	Adaptor Proteins Implicated
Orientia tsutsugamushi	Rodents, Leptotromibidium mites	Not Known	Leptotromibidium ^*	Endothelial Cells, Neutrophils, Monocytes/Macrophages, Dendritic Cells	Cytosol	TLR2 [63] TLR4 [61] RIG-I [64] NLRC5 [65] Mincle [49]	STING [64]
Rickettsia spp.	Various: Rodents, Dogs, Forest animals (opossums, squirrels)	Not Known	Various: Dermancentor, Ixodes, Amblyomma, Bothriocroton, Rhipicephalus, Rhizomucor, more	Endothelial Cells, Macrophages	Cytosol	TLR2 [78] TLR4 [76–78] NLRP3 [80]	Myd88 [74] ASC [77, 80]
Anaplasma phagocytophilum	Forest animals (mice, skunks, deer), Horses, Household pets	Not Known	Ixodes^, Amblyomma, Dermacentor*	Neutrophils	Vacuole	NOD2 [98] NLRC4 [100] TLR2 [96]	RIP2 [98] MyD88 [98] STAT1 [96]
Ehrlichia chaffeensis	White-tailed deer^*, coyotes, dogs	Not Known	Amblyomma^, Ixodes, Dermacentor*	Monocytes/Macrophages	Vacuole	TLR2 [111, 113] TLR7 [111] TLR9 [114] NOD2 [113]	Myd88 [112]
Coxiella burnetii	Animal livestock (goats, cattle, sheep, dairy cows), Birds, Reptiles, Arthropods (Ixodes, Dermacentor, Haemaphysalis)	Fluid secretions (amniotic fluid, feces, vaginal secretions, urine) ^*, Unpasteurized Milk	Not Known	Monocytes/Macrophages	Vacuole	NOD2 [135] TLR1 [135] TLR2 [137, 138] TLR4 [137]	MyD88 [135–137] TRIF [137] Myd88, TRIF [137]

Denotes primary mode of transmission