title: Technique for determining the bactericidal effect of drug combinations.
abstract: Two paper strips, each containing different antimicrobial agents, were placed on plates on Mueller-Hinton agar to permit antibiotic to enter the agar. A filter membrane was placed on this plate, and the microorganisms were planted on the membrane. After 6 h of incubation at 37 C, the membrane was transferred to antibiotic-free Mueller-Hinton agar containing triphenyltetrazolium hydrochloride and incubated for 18 h at 37 C. Specific growth patterns were indicative of additive (indifferent), synergistic, or antagonistic effects of the drug combination used. Trimethoprim and sulfamethoxazole proved to act synergistically against 85% of Escherichia coli, 86% of Klebsiella, and 89% of Proteus mirabilis strains tested. A few strains resistant to either drug were susceptible to their combination. The technique was useful against organisms with widely differing susceptibilities to the two antimicrobial agents tested.
authors.forename: V
authors.initials: V
authors.lastname: Lorian
authors.forename: G
authors.initials: G
authors.lastname: Fodor
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002476:Cellophane; D024881:Drug Resistance, Bacterial; D004357:Drug Synergism; D004755:Enterobacteriaceae / Q000187:drug effects*; D004926:Escherichia coli / Q000187:drug effects; D007709:Klebsiella / Q000187:drug effects; D008828:Microbiological Techniques; D011513:Proteus mirabilis / Q000187:drug effects; D013420:Sulfamethoxazole / Q000494:pharmacology*; D014295:Trimethoprim / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D002476:Cellophane; D014295:Trimethoprim; D013420:Sulfamethoxazole