TABLE 2.

ARB identified to date^a

ARB	Hostb	Life-style	Pathogenicity	Reference
α proteobacteriad
Afipia felis	Acanthamoeba	Facultative intracellular	Unknown	157
Afipia broomae	Acanthamoeba	Facultative intracellular	Unknown	155
Bosea spp.	Acanthamoeba	Facultative intracellular	Unknown	154
Bradyrhizobium japonicum	Acanthamoeba	Facultative intracellular	Unknown	155
Caedibacter acanthamoebae	Acanthamoebac	Facultative intracellular	Unknown	114
Ehrlichia-like organism	Saccamoebac	Obligate intracellular	Unknown	182
Mezorhizobium amorphae	Acanthamoeba	Extracellular	Unknown	155
Odyssella thelassonicensis	Acanthamoeba	Facultative intracellular	Unknown	27
Paracaedibacter symbiosus	Acanthamoebac	Facultative intracellular	Unknown	114
Paracaedibacter acanthamoebae	Acanthamoebac	Facultative intracellular	Unknown	114
“Rasbo bacterium”	Acanthamoeba	Extracellular	Unknown	150
Rickettsia-like	Acanthamoeba	Obligate intracellular	Potential	80
β proteobacteriad
Burkholderia cepacia	Acanthamoeba	Extracellular	Established	148, 168
Burkholdereria pseudomallei	Acanthamoeba	Extracellular	Established	127
Procabacter acanthamoeba	Acanthamoebac	Facultative intracellular	Unknown	115
Ralstonia pickettii	Acanthamoebac	Extracellular	Potential	180
γ proteobacteriad
Coxiella burnetii	Acanthamoeba	Obligate intracellular	Established	158
Escherichia coli O157	Acanthamoeba	Extracellular	Established	17
Francisella tularensis	Acanthamoeba	Facultative intracellular	Established	25
Legionella pneumophila	Many species	Facultative intracellular	Established	209
Legionella anisa	Acanthamoeba	Facultative intracellular	Potential	156
Legionella lytica (formerly Sarcobium lyticum)	Acanthamoeba	Facultative intracellular	Potential	66, 67
L. fallonii	Acanthamoeba	Facultative intracellular	Potential	5
L. rowbothamii	Acanthamoeba	Facultative intracellular	Potential	5
L. drozanskii	Acanthamoeba	Facultative intracellular	Potential	5
L. drancourtii	Acanthamoeba	Facultative intracellular	Potential	151
Other LLAP	Acanthamoeba	Facultative intracellular	Potential	212
Pseudomonas aeruginosa	Acanthamoebac	Extracellular	Established	178
Vibrio cholerae	Acanthamoeba, Naegleria	Extracellular	Established	237
ɛ proteobacteria
Helicobacter pylori	Acanthamoeba	Facultative intracellular	Established	248
Chlamydiaed
Chlamydophila pneumoniae	Acanthamoeba	Obligate intracellular	Established	71
Neochlamydia hartmanellae	Hartmanellac	Obligate intracellular	Potential	118
Parachlamydia acanthamoebae	Acanthamoebac	Obligate intracellular	Potential	7
Simkania negevensis	Acanthamoeba	Obligate intracellular	Established	133
Flavobacteria
Amoebophilus asiaticus	Acanthamoebac	Obligate intracellular	Unknown	116
Flavobacterium spp.	Acanthamoeba	Facultative intracellular	Unknown	116, 187
Bacilli
Listeria monocytogenes	Acanthamoeba	Facultative intracellular	Established	163
Actinobacteriad
Molibuncus curtisii	Acanthamoeba	Extracellular	Potential	241
Mycobacterium leprae	Acanthamoeba	Obligate intracellular	Established	129
Mycobacterium avium	Acanthamoeba	Facultative intracellular	Established	45, 141, 224
Mycobacterium marinum	Acanthamoeba	Facultative intracellular	Established	45, 141
Mycobacterium ulcerans	Acanthamoeba	Facultative intracellular	Established	141
Mycobacterium simiae	Acanthamoeba	Facultative intracellular	Potential	141
Mycobacterium phlei	Acanthamoeba	Facultative intracellular	Potential	141
Mycobacterium fortuitum	Acanthamoeba	Facultative intracellular	Potential	45, 141
Mycobacterium smegmatis	Acanthamoeba	Facultative intracellular	Potential	141

^aAmong the ARB, some are natural hosts of free-living amoebae (identified within free-living amoebae isolated by amoebal enrichment), some were recovered by amoebal coculture (i.e., using as the cell background free-living amoebae), and some were found to be resistant to a given amoebal “host” in vitro. Some are obligate intracellular bacteria, while others are facultative intracellular bacteria or extracellular bacteria. Some are established human pathogens, while other are emerging potential pathogens, or, until now, strictly environmental species. The list does not include Enterobacteriaceae that have been shown to resist destruction by free-living amoebae only under non-physiological conditions, such as chlorination (137).

^bNatural host, or grown by amoebal coculture.

^cNatural host.

^dClass, according to reference 86.