Bactericidal effects of antimicrobial agents on epithelial cell-associated Pseudomonas aeruginosa

It is not clear whether antipseudomonal agents can kill cell-associated bacteria within a short time. Madin–Darby canine kidney (MDCK) and A549 cells were infected with Pseudomonas aeruginosa ATCC 27853 and PAO1 and the bactericidal activity of ceftazidime, imipenem, meropenem, gentamicin, and ciprofloxacin against the organisms was investigated. In both MDCK and A549 cells, β-lactams could not kill epithelial cell-associated bacteria within 2 h. Gentamicin at concentrations ≤32 μg/ml killed more than 99% of epithelial cell-associated bacteria. Ciprofloxacin at 0.5 μg/ml killed more than 99.9% of MDCK cell-associated bacteria. Ciprofloxacin has the strongest and most rapid bactericidal activity against epithelial cell-associated bacteria, which may be explained by the combination of potent in-vitro bactericidal activity and high penetration ability into epithelial cells.