Effect of various antibiotics on Listeria monocytogenes multiplying in L 929 cells

Various antibiotics were evaluated as to their effect on Listeria monocytogenes SLCC 4013 multiplying within L 929 mouse fibroblast cells. Antibiotics were employed in concentrations above the MIC value. However, there was no measurable effect of some drugs on intracellular listeriae (azlocillin, mezlocillin, cephalothin, ciprofloxacin, chloramphenicol). With other drugs an inhibition of intracellular growth was observed (penicillin, ampicillin, rifampicin, rifapentine, erythromycin, doxycycline, co-trimoxazole, coumermycin). Notably, with none of the antibiotics a complete eradication of the listeriae was achieved. There is a good correlation of these results with animal experiments. Therefore, the cell culture system might be useful for the screening of new antibiotics.