Application of Cell Culture in Studying Antibacterial Activity of Rifampicin toShigellaand EnteropathogenicEscherichia coli

Antibacterial activity of rifampicin (RFP) against intracellularShigellaand enteropathogenicEscherichia coliwas tested in a cell culture system and compared with that of known active controls such as chloramphenicol (CP), kanamycin (KM), streptomycin (SM) or tetracycline (TC), with reference to minimal inhibitory concentrations (MIC) and to chemotherapeutic effects on intraperitoneal infections in mice. When RFP, CP, or TC was applied to L cells and HeLa cells infected respectively withShigella flexneri2a and enteropathogenicE. coli0143, both cell‐infection and intracellular multiplication of the bacilli were considerably inhibited, while RFP was less active against the extracellular bacilli in cell‐free environments than KM and SM. Comparing the intracellular antibacterial activity between RFP and TC or CP, the former was less active than the latter two. This discrepancy in antibacterial activity between extra‐ and intracellular environments could in part be attributed to the fact that RFP penetrated more easily into cultured cells than KM and SM did.