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Updated: Aug 10, 2026

Diagonal Method to Measure Synergy Among Any Number of Drugs
Published on: June 21, 2018
Synergic activity of D-cycloserine and beta-chloro-D-alanine against Mycobacterium tuberculosis
1Unit of Mycobacteriology and Centro de Malária e outras Doenças Tropicais /IHMT/Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisbon, Portugal. suzanadavid@ihmt.unl.pt
Abstract:
D-Cycloserine (DCS) is a peptidoglycan inhibitor. Although very effective against Mycobacterium tuberculosis, it is seldom employed in the management of this infection due to its high toxicity. beta-Chloro-D-alanine (another peptidoglycan inhibitor) reduces the MIC of DCS from 50 to 2.5 mg/L at a concentration significantly below its MIC for this organism. A reduction in bacterial viability and significant growth inhibition (as quantified by the X/Y quotient for the Bactec radiometric procedure) were observed with subinhibitory concentrations of both drugs. It is suggested that this powerful synergic effect should be the object of in vivo and eventually clinical trials.
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