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Mode of Action and Synergy of Ceftazidime and Baicalein against Streptococcus pyogenes
Abstract
Purpose: To investigate the antibacterial activity of baicalein used alone, or in combination with ceftazidime, against Streptococcus pyogenes.
Methods: Minimum inhibitory concentration (MIC), checkerboard assay parameters, and viability curves were determined for S. pyogenes DMST 30653, 30654, and 30655. Cytoplasmic membrane (CM) permeability technique, enzyme assays, transmission electron microscopy and Fourier transforminfrared microspectroscopy were used to investigate the changes in the bacterial biomolecules.
Results: The MIC of ceftazidime and baicalein against all the S. pyogenes strains were 0.50 and > 256.0 μg/ml, respectively. A synergistic effect against these strains was exhibited by the ceftazidime/baicalein combination (fractional inhibitory concentration index, < 0.37). The results for the viable counts indicate that this synergistic activity was present. Baicalein exerted inhibitory activity against β-lactamase. Compared with the controls, combining baicalein with ceftazidime caused peptidoglycan and morphological damage, significantly increased CM permeability and protein concentrations, and decreased cellular fatty acid and nucleic acid concentrations.
Conclusion: Baicalein is a potential synergistic adjunct to ceftazidime for the treatment of S. pyogenes infections.
Keywords: Streptococcus pyogenes, Cytoplasmic membrane permeability, Baicalein, Ceftazidime, Synergistic activity, Fourier Transform-infrared microspectroscopy, Transmission electron microscopy
