TABLE 3.

Effect of nonvirulent dnaK-KO B. suis on monocyte apoptosis^a

Monocytes	% of apoptotic cells	No. of viable bacteria/well at h of infection:
		1.5	6	24
Resting	42 ± 9
B. suis infected	9 ± 3b	85,000 ± 1,800	43,000 ± 1,200	625,000 ± 9,000
dnaK-KO B. suis infected	43 ± 12b	48,000 ± 1,200	12,500 ± 100	<5

^aHuman monocytes were infected (or not) with B. suis or dnaK-KO B. suis (MOI = 20) in eight-chamber culture slides. Forty-eight hours later, the percentages of apoptotic cells in the different eight-chamber culture slides were measured by microscopy with fluorescein-labeled annexin V. Parallel experiments were performed to measure phagocytosis and development of B. suis or dnaK-KO B. suis within cells. Human monocytes (5 × 10⁵/well) were infected with B. suis or with dnaK-KO B. suis (MOI = 20) in 24-well microplates. At different times postinfection (1.5, 6, and 24 h), infected cells were lysed after gentamicin had killed extracellular bacteria. The number of intracellular viable bacteria was then determined on agarose plates and expressed as CFU per well as previously described (2, 3). Values are means and standard deviations from four different experiments. 

^bSignificantly different (P < 0.02) as shown by a paired t test.