TABLE 3.

Invasiveness and OM properties of rough B. abortus and B. ovis

Characteristic	B. abortus S19a	B. abortus 45/20	B. abortus RB51	B. ovis REO 198	Reference
Invasiveness to host and cellsb
Ovine infection	Moderate	Moderate	Moderate	Severe	8, 12, 17
Bovine infection	Moderate	Moderate	Moderate	None	1, 8, 21
No. (%) of bacterium-associated cells after 2 h	75	98	100	12	22, 23, 27
No. of adherent bacteria per cell after 2 h	4	40	38	4	22, 23, 27
No. of intracellular bacteria per cell after 2 h	1–2	20	18	0–1	22, 23, 27
No. of CFU within cells at 48 h	5 × 105	6.2 × 106	NDc	0	22, 23, 27
No. (%) of infected cells dead at 48 h	0	73	ND	0	22, 23
Bacteria outside lysosomes	+	++	ND	−	22, 23, 27
Skin reaction of B. melitensis-infected animals	Positive	Positive	ND	Negative	13, 26
OM properties
Reactivity with polyclonal anti-B. canis R-LPS	Total	Total	Total	Partial	18, unpublished data
Access to surface R epitopes	+	++++	++++	++++	4
Estimated no. of anti-O chain gold conjugate particles per bacterial cell	3,000–5,000	0–12	0	0	4, 10, 26, this work
Heterogeneity of R-LPS in SDS-PAGE (no. of bands)	1	4	3	1	10, 26
OM protein 25	Complete	Complete	Complete	Truncated	4, 7
OM protein 31	Absent	Absent	Absent	Present	4, 29
Sensitivity to hydrophobic antibiotics	+	++	ND	++++	15
Maximal uptake of NPN (s)	200	200	200	10	This work
Binding of polymyxin B by LPS	+	++	++	++++	16, this work
Sensitivity to cationic peptides	+	++	++	++++	16, this work

^aThis is an attenuated vaccine strain. Virulent B. abortus 2308 induces severe infections, penetrates cells at an efficiency of close to 100%, evades lysosomes, and replicates within cells (23). LPS preparations from smooth Brucella contain close to 10% of rough-type LPS displayed in a single band in SDS-PAGE (10). −, absent; +, present in <25%; ++, present in >25% to <50%; ++++, present in >75%. 

^bTested in human epithelial HeLa cells. 

^cND, not done with RB51.