The Mode of Action of Antibiotic Synergism and Antagonism: the Effect in Vitro on Bacteria not Actively Multiplying

Abstract

Antibiotics were added to washed cell suspensions in distilled water of the following organisms - Streptococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli, and to the same organisms in nutrient broth. Neomycin, polymyxin, and streptomycin were more effective in the water suspensions, oxytetracycline and bacitracin were effective in either, and penicillin was effective only in broth. Synergistic and antagonistic effects of pairs of antibiotics, demonstrable in broth, were not observed in the absence of nutrients.