Antimicrobial Activity of Trichosetin Against Local Clinical Methicillin-Resistant Staphylococcus aureus (MRSA) Isolates

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is a multi-drug resistant bacteria that has a thinning reservoir of drugs effective against the numerous clinical problems associated with it. A recent study established the presence of antimicrobial activity of a tetramic acid antibiotic, Trichosetin, against a foreign strain of MRSA (ATCC 33591). This study aimed to determine the presence of antimicrobial property of Trichosetin against clinical MRSA strains isolated in the Philippines by finding the minimum inhibitory concentration (MIC). Using the National Committee for Clinical Laboratory Standards protocol for microtiter-based MIC assay, the antimicrobial activity of Trichosetin against nine local clinical MRSA isolates was evaluated. The solvent of Trichosetin which is methanol was also screened against the MRSA isolates. The positive control used was Vancomycin HCI. Results showed that Trichosetin manifested a strong antimicrobial activity against MRSA isolates 1, 2, 3, 5, 6, 7, and 8, with MIC of 0.78 pg/ml, 5.72 pg/ml, 6.51 pg/ml, 0.78 pg/ml, 0.78 pg/ml, 0.78 pg/ml and 1.82 pg/ml, respectively. It also showed a moderate inhibitory activity against the MRSA strains 4 and 9 with MIC of 12.76 pg/ml and 33.33 pg/ml. Statistical analyses have shown that the differences between the nine local clinical MRSA isolates, and the difference between the inhibitory activities of Trichosetin and Vancomycin have a significant effect on the study.