Antibacterial Activity of Rationally Designed Antimicrobial Peptides

Many infectious diseases are still prevalent in the world's populations since no effective treatments are available to eradicate them. The reasons may either be the antibiotic resistance towards the available therapeutic molecules or the slow rate of producing adequate therapeutic regimens to tackle the rapid growth of new infectious diseases, as well as the toxicity of current treatment regimens. Due to these reasons, there is a need to seek and develop novel therapeutic regimens to reduce the rapid scale of bacterial infections. Antimicrobial Peptides (AMPs) are components of the first line of defense for prokaryotes and eukaryotes and have a wide range of activities against Gram-negative and Gram-positive bacteria, fungi, cancer cells, and protozoa, as well as viruses. In this study, peptides which were initially identified for their HIV inhibitory activity were further screened for antibacterial activity through determination of their kinetics as well as their cytotoxicity. From the results obtained, the MICs of two AMPs (Molecule 3 and Molecule 7) were 12.5 μg/ml for K. pneumoniae (ATCC 700603) and 6.25 μg/ml for P. aeruginosa (ATCC 22108). The two AMPs killed these bacteria rapidly in vitro, preventing bacterial growth within few hours of treatment. Furthermore, the cytotoxic activity of these two peptides was significantly low, even at an AMP concentration of 100 μg/ml. These results revealed that Molecule 3 and 7 have great potential as antibacterial drugs or could serve as lead compounds in the design of therapeutic regimens for the treatment of antibiotic-resistant bacteria.