For determination of intracellular viable bacteria, after 1, 3 and 6 hours of incubation, infected J774 monolayers were washed six times with PBS and treated with 150 μg/mL gentamicin sulphate (Sigma-Aldrich, USA) diluted in DMEM for 1 h. The number of intracellular bacteria was determined by viable counts after lysis of monolayers with 0.5 mL of 0.1% TritonX-100 (Sigma-Aldrich, USA) in PBS.