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Updated: Jul 1, 2025

Deferred Growth Inhibition Assay to Quantify the Effect of Bacteria-derived Antimicrobials on Competition
Published on: September 3, 2016
Inhibitory action of antibiotics on Kluyveromyces marxianus
Rafael Lisandro Althaus1, Orlando Guillermo Nagel1, Dafna Eluk1
1Facultad de Ciencias Veterinarias, Universidad Nacional del Litoral - R.P.L. Kreder 2805, 3080 Esperanza, Argentina.
Abstract:
A bioassay containing Kluyveromyces marxianus in microtiter plates was used to determine the inhibitory action of 28 antibiotics (aminoglycosides, beta-lactams, macrolides, quinolones, tetracyclines and sulfonamides) against this yeast in whey. For this purpose, the dose-response curve for each antibiotic was constructed using 16 replicates of 12 different concentrations of the antibiotic. The plates were incubated at 40°C until the negative samples exhibited their indicator (5-7h). Subsequently, the absorbances of the yeast cells in each plate were measured by the turbidimetric method (λ=600nm) and the logistic regression model was applied. The concentrations causing 10% (IC10) and 50% (IC50) of growth inhibition of the yeast were calculated. The results allowed to conclude that whey contaminated with cephalosporins, quinolones and tetracyclines at levels close to the Maximum Residue Limits inhibits the growth of K. marxianus. Therefore, previous inactivation treatments should be implemented in order to re-use this contaminated whey by fermentation with K. marxianus.
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