Antibacterial and synergic effects of gallic acid-grafted-chitosan with β-lactams against methicillin-resistant Staphylococcus aureus (MRSA).
Methicillin-resistant Staphylococcus aureus (MRSA) is spreading worldwide, emphasizing the need to search for new antibiotics. The anti-MRSA activities of gallic acid-grafted-chitosans (GA-g-chitosans) were investigated against 2 MRSA standards and 10 MRSA clinical isolates by determining the minimum inhibitory concentrations (MICs). GA-g-chitosan (I), which has the highest gallic acid content, exhibited the strongest anti-MRSA activities, with MICs of 32-64 μg/mL. A time-kill investigation revealed that GA-g-chitosan (I) exhibited a bactericidal effect at twice the MIC, also demonstrating good thermal and pH stability. Investigation of cell envelope integrity showed the release of intracellular components with an increasing absorbance value at 260 nm, indicating cell envelope damage caused by the GA-g-chitosan (I), which was further confirmed by transmission electron microscopy. When GA-g-chitosans were combined with β-lactams, including ampicillin and penicillin, synergistic effects were observed on the 2 standard MRSA strains and on the 10 clinical isolates, with fractional inhibitory indices ranging from 0.125 to 0.625. In the time-kill dynamic confirmation test, synergistic bactericidal effects were observed for the combinations of GA-g-chitosans with β-lactams, and over 4.0 log CFU/mL reductions were observed after 24 h when combination treatment was used. These results may prove GA-g-chitosans to be a potent agent when combined with ampicillin and penicillin for the elimination of MRSA.
['Lee|Dae-Sung|DS|', 'Eom|Sung-Hwan|SH|', 'Kim|Young-Mog|YM|', 'Kim|Hye Seon|HS|', 'Yim|Mi-Jin|MJ|', 'Lee|Sang-Hoon|SH|', 'Kim|Do-Hyung|DH|', 'Je|Jae-Young|JY|']
D000900:Anti-Bacterial Agents D048271:Chitosan D015169:Colony Count, Microbial D004355:Drug Stability D004357:Drug Synergism D005707:Gallic Acid D006358:Hot Temperature D006863:Hydrogen-Ion Concentration D055624:Methicillin-Resistant Staphylococcus aureus D008826:Microbial Sensitivity Tests D046529:Microscopy, Electron, Transmission D047090:beta-Lactams
MRSA cell envelope SARM activité antibactérienne antibacterial activity chitosan chitosane effet synergique enveloppe cellulaire synergy effect