Baicalin Synergy with β-Lactam Antibiotics Against Methicillin-resistant Staphylococcus aureus and Other β-Lactam-resistant Strains of S. aureus

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Abstract
Bacterial resistance to antibiotics is a serious global problem and includes strains of β-lactam-resistant Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). Novel antimicrobials and/or new approaches to combat the problem are urgently needed. The Chinese herb Xi-nan Huangqin (Scutellaria amoena CM. Wright) has been used in traditional Chinese medicine to treat a wide range of infectious diseases. In this study we have examined the antibacterial action of baicalin, a flavone isolated from the herb. When combined with 16 μg mL−1 baicalin, minimum inhibitory concentrations (MICs) of benzylpenicillin against MRSA and penicillin-resistant S. aureus were reduced from 125 and 250 μg mL−1 to 4 and 16 μg mL−1, respectively. This activity of baicalin was dose-dependent. Viable counts showed that the killing of MRSA and β-lactam-resistant S. aureus cells by 10 to 50 μgm mL−1 ampicillin, amoxycillin, benzylpenicillin, methicillin and cefotaxime was potentiated by 25 μg mL−1 baicalin. From the study it was concluded that baicalin has the potential to restore the effectiveness of β-lactam antibiotics against MRSA and other strains of β-lactam-resistant S. aureus. In view of its limited toxicity baicalin offers potential for the development of a valuable adjunct to β-lactam treatments against otherwise resistant strains of microorganisms.