TABLE 1.

Flow cytometric assessment of initial M/M infection by rough and smooth Brucella^g

Opsonic treatment	Strain	Mean ± SD
		% M/M infecteda	MFI infectedc	Rough/smooth MFI ratiod	Bacterial infection indexe
Medium	WRR51/GFP	21 ± 5	60.1 ± 9.8	NAf	903 ± 335
Medium	16M/GFP	2.6 ± 0.8b	2.5 ± 0.8b	23.8 ± 11.2	5 ± 3b
Medium	WRR51/GFP+wboA	1.9 ± 0.4b	2.2 ± 0.8b	27.6 ± 14.5	3 ± 2b
HS	WRR51/GFP	82 ± 8.8	68.3 ± 12.2	NA	5,108 ± 1,295
HS	16M/GFP	40.3 ± 11.9b	4.7 ± 1.3b	14.5 ± 3.5	153 ± 49b
HS	WRR51/GFP+wboA	25.7 ± 9.4b	3.4 ± 0.5b	19.9 ± 3.8	58 ± 29b

^a% infected = % cells positive in FL1 intensity.

^bP < 0.05 versus cells infected with WRR51/GFP.

^cMFI of FL1 positive cells − MFI of FL1 negative cells. This is an indicator of how many bacteria are present per infected M/M.

^dRatio of MFI of infected rough to smooth strains.

^e% infected M/M × MFI of infected M/M.

^fNA, nonapplicable.

^gM/M monolayers were treated with bacteria at a multiplicity of infection of 50:1 in the presence of medium or medium supplemented with 1% HS. One hour later, monolayers were washed to remove nonadherent bacteria. M/M were scraped from the well, washed, fixed in formaldehyde, and acquired on a flow cytometer. FL1-positive cells were defined as those with a fluorescence intensity greater than the fluorescence intensity of 97.5% of untreated control cells. Data are means ± SD for four experiments.