Effect of Bioactive Peptide, KR-12-a5, on Growth of Clinical Methicillin-resistant Staphylococcus aureus Isolates

Staphylococcus aureus is one of the most frequent infectious agents causing hospitals and community associated infections. Developing the treatment for methicillin resistant S. aureus (MRSA) is a challenging arena for effective therapeutics. Application of antimicrobial peptides is an alternative option to control MRSA infection. The potential of the bioactive peptide against MRSA was previously revealed; however, the study on the effect of KR-12-a5 on the various clinical MRSA growth was not elucidated. This study aimed to investigate the effect of bioactive peptide KR-12-a5 on the growth of MRSA isolated from patients. Evaluation of KR-12-a5 peptide using antimicrobial susceptibility test was performed. Antimicrobial activity assay showed that the KR-12-a5 at 2-64 μM could inhibit the growth of S. aureus ATCC 29213 in the range of 55.0±0.8%-81.0±6.2%. In case of KR-12-a5 treatment at 2, 4, and 8 μM, growth of all twenty clinical MRSA isolates could be inhibited less than 90% in the range of 0.0-75.9±1.6%, 0.0-73.0±4.2%, and 0.0-77.1±1.7%, respectively. Whereas the treatment of those at 16, 32, and 64 μM, growth of clinical MRSA could be significantly inhibited more than 90% (p < 0.05) in the range of 94.3±6.7%-100.4±0.4% in 3 isolates (15%), 97.3±0.3%-99.5±0.2% in 4 isolates (20%), and 91.6±0.8%-99.0±0.1% in 9 isolates (45%), respectively. These findings indicated that the KR-12-a5 effectively controls growth of both S. aureus ATCC 29213 and clinical MRSA isolates