The Mechanism of Antimicrobial Activity of Sophoraflavanone B Against Methicillin-ResistantStaphylococcus aureus

Abstract

Sophoraflavanone B (SPF-B), a prenylated flavonoid, can be isolated from the roots of Desmodium caudatum. The aim of this study was to determine the mechanism of SPF-B's antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA). MRSA is a multidrug-resistant pathogen and the main cause of hospital- and community-acquired infections. The minimum inhibitory concentration (MIC) of SPF-B was assessed using the broth microdilution method. The mechanism of action of SPF-B on S. aureus was analyzed in combination assays incorporating detergents, ATPase inhibitors, and peptidoglycan (PGN) derived from S. aureus. Furthermore, morphological changes in the SPF-B-treated MRSA strains were investigated using transmission electron microscopy. The MIC of SPF-B for MRSA was in the range of 15.6-31.25 μg/mL. The mechanism of action of SPF-B on MRSA was investigated using combination assays with detergent and ATPase inhibitors. The optical density at 600 nm of MRSA suspensions treated with a combination of detergent and SPF-B reduced the MRSA by 63%-73%. In the SPF-B and PGN combination assay, direct binding of SPF-B with PGN from S. aureus was evident. These data may be validated for the development of new antibacterial drugs for low MRSA resistance.

Methyl Gallate from Galla rhois Successfully Controls Clinical Isolates of Salmonella Infection in Both In Vitro and In Vivo Systems

“…MG is known to perform a wide spectrum of biological activities, but its mechanism for antibacterial activity against Salmonella remains unclear. We hypothesized that there is synergy between MG and bacterial membrane permeablization/binding agents such as tris(hydroxymethyl)aminomethane (TRIS), triton X-100 (TX) [16]–[18]. MG may be responsible for its increased antibacterial activity against Salmonella .…”

“…MG may be responsible for its increased antibacterial activity against Salmonella . Second, MG may exert its inhibitory effect on the bacterial replication by inhibiting cytochrome oxidase or by inhibition of proton-driven ATPases [16]–[18]. As a result, we decided to investigate the in vitro activities of MG separately or in combination with the bacterial membrane- binding agents TRIS and TX, and the ABC transporter-inhibiting agents NaN3 and inhibitor of proton-driven ATPases N,N′ -Dicyclohexylcarbodiimide (DCCD).…”

In vitro Potential Effect of Morin in the Combination with β-Lactam Antibiotics Against Methicillin-Resistant Staphylococcus aureus

“…Methicillin was first used clinically in 1959 and only 2 years later MRSA was isolated (Moellering, 2012;Mun et al, 2014). MRSA is generated when methicillinsusceptible S. aureus acquires the mecA gene (the structural gene for the penicillin-binding protein, PBP2a), enabling the bacteria to sustain cell-wall synthesis.…”

“…The checkerboard method was used to identify the interactions between morin and b-lactam antibiotic (Mun et al, 2014). The antimicrobial assay was performed with morin in combination with ampicillin and oxacillin.…”

“…To perform the viability assay, the synergistic effects of morin and b-lactam antibiotics were determined on the bacterial growth in 96-well plates at 5 different points of time (0, 4, 8, 16, and 24 h) (Mun et al, 2014). The bacterial cultures incubated in MHA for 24 h at 37°C were diluted with fresh MHB to 1.5 · 10 5 CFU/mL, and the diluted cultures were preincubated at 37°C for 24 h. Aliquots (0.1 mL) of the culture were taken at 0, 4, 8, 16, and 24 h of incubation, and serial 10-fold dilutions were prepared in saline as needed.…”