Methicillin/per-6-(4-methoxylbenzyl)-amino-6-deoxy-β-cyclodextrin 1:1 complex and its potentiation in vitro against methicillin-resistant Staphylococcus aureus

Some of beta-cyclodextrin (beta-CD) derivatives as host compounds can form specific inclusion complexes with guest drugs in defined shapes and conformations. In observing one of the known mechanisms of action of beta-lactam antibiotic-resistances, a unique beta-CD derivative/antibiotic complex may act in accommodating the antibiotic to increase affinity for the resistant target such as the altered penicillin-binding protein PBP2a, which results in recovering and potentiating its antibacterial activities against resistant strains. A designed beta-CD derivative, per-6-(4-methoxylbenzyl)-amino-6-deoxy-beta-CD HCl salt (1), was synthesized from starting material beta-CD. The formation and the conformation of 1:1 (molar ratio) methicillin/compound 1 complex was determined through H-1 NMR and NOESY experiments. The in vitro MIC of the methicillin in combination of 1, along with methicillin alone, and 1:1 hydroxypropyl-beta-CD (HP-beta-CD, a commercially available product)/methicillin were assayed against two methicillin-resistant Staphylococcus aureus (MRSA) strains. The MIC values of methicillin combined with 1 against MRSA COL and MRSA USA300 were significantly decreased with 30- to 60-fold, compared with those for the antibiotic alone, and 1:1 HP-beta-CD/methicillin in this assay. This revealed that compound 1 recovered/potentiated methicillin against MRSA COL and MRSA USA300 in vitro combined with methicillin at 1:1 compound 1/methicillin in the aqueous solution.