Table 3.

Effect of nonvirulent dnaK-KO B. suis on monocyte apoptosisa

Monocytes% of apoptotic cellsNo. of viable bacteria/well at h of infection:
Resting42 ± 9
B. suisinfected9 ± 3b 85,000 ± 1,80043,000 ± 1,200625,000 ± 9,000
dnaK-KO B. suisinfected43 ± 12b 48,000 ± 1,20012,500 ± 100<5
  • a Human 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 ordnaK-KO B. suis within cells. Human monocytes (5 × 105/well) were infected with B. suisor 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.

  • b Significantly different (P < 0.02) as shown by a paired t test.