Effect of subinhibitory concentrations of antimicrobial agents on virulence factors of Shigella flexneri 2a and Escherichia coli O124.

The effect of subinhibitory concentrations of rifampicin, chloramphenicol, tetracycline and nalidixic acid on the interaction of Shigella flexneri 2a and Escherichia coli O124 with HeLa cells was examined. Antimicrobial agents altered adhesion, penetration and intracellular multiplication of the bacteria, as well as re-infection of adjacent cells. Chloramphenicol increased the virulence of the bacterial strains whereas nalidixic acid, tetracycline and rifampicin diminished it.