Table 2.

Sensitivity of B. abortus strains to different stresses^a

Strain	Sensitivity to stress			Sensitivity to detergent (log CFU)e
	Osmotic (log CFU)b	Acidic (log CFU)c	Oxidative (mm)d	DOC	Zwittergent 3-16	Sarkosyl	Triton
Wild-type 2308	6.03 ± 0.11	5.47 ± 0.06	8.0 ± 1.4	6.47 ± 0.01	4.65 ± 0.21	4.79 ± 0.01	5.63 ± 0.21
ΔcypAB mutant	6.07 ± 0.05	2.91 ± 0.13	13.5 ± 0.7	4.54 ± 0.09	1.85 ± 0.07	2.81 ± 0.04	5.59 ± 0.08
ΔcypAB(pDK51) mutant	ND	2.67 ± 0.21	12.5 ± 0.7	4.54 ± 0.09	1.90 ± 0.14	2.84 ± 0.08	ND
ΔcypAB(pcypA) mutant	ND	5.38 ± 0.05	7.0 ± 0.0	6.50 ± 0.01	4.40 ± 0.14	4.72 ± 0.04	ND
ΔcypAB(pcypB) mutant	ND	5.42 ± 0.01	7.5 ± 0.7	7.13 ± 0.25	4.50 ± 0.28	5.10 ± 0.04	ND
ΔcypAB(pcypAB) mutant	ND	5.20 ± 0.02	7.5 ± 0.7	7.09 ± 0.12	4.75 ± 0.07	4.89 ± 0.08	ND
ΔcypAB(pcypBR55A/F60A) mutant	ND	ND	10.5 ± 0.7	5.12 ± 0.09	2.65 ± 0.21	3.25 ± 0.01	ND

^aStatistical significance was evaluated by Student's t test. The results are representative of three independent experiments. ND, not determined.

^bDilutions of different B. abortus strains were plated in duplicate onto LB agar containing 250 mM NaCl. Plates were incubated for 72 h, and the number of CFU was scored.

^cSensitivity to acidic stress was determined after exposure of different B. abortus strains to citrate buffer (pH 3.5) for 1 h at 37°C as described in Materials and Methods. Cells were serially diluted and plated on TSB agar in order to determine cell viability.

^dSensitivity to oxidative stress was studied by the disk diffusion assay using 10 μl of 10% peroxide hydrogen (H₂O₂) for B. abortus strains as described in Materials and Methods. The values shown represent the inhibition zone diameters (mm).

^eFor the detergent sensitivity assay, dilutions of different B. abortus strains were plated in duplicate onto TSB agar plates containing Sarkosyl (125 μg/ml), deoxycholate (DOC) (1,000 μg/ml), Zwittergent 3-16 (25 μg/ml), or Triton X-100 (10%). Plates were incubated for 72 h, and the number of CFU was scored.