Research Article Antibacterial Activity of Rationally Designed Antimicrobial Peptides Marius B. Tincho , 1 Thureyah Morris , 2 Mervin Meyer , 3 and Ashley Pretorius 1 1 Bioinformatics Research Group (BRG), DST/Mintek Nanotechnology Innovation Centre–Biolabels Node, Department of Biotechnology, Faculty of Natural Sciences, University of the Western Cape, Bellville 7535, South Africa 2 Food Toxicology Laboratory, Department of Medical Bioscience, Faculty of Natural Sciences, University of the Western Cape, Bellville 7535, South Africa 3 DST/Mintek Nanotechnology Innovation Centre–Biolabels Node, Department of Biotechnology, Faculty of Natural Sciences, University of the Western Cape, Bellville 7535, South Africa Correspondence should be addressed to Marius B. Tincho; 3173772@myuwc.ac.za and ureyah Morris; tmorris@uwc.ac.za Received 21 October 2019; Accepted 10 March 2020; Published 8 April 2020 Academic Editor: Clemencia Chaves-L´ opez Copyright © 2020 Marius B. Tincho et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Manyinfectiousdiseasesarestillprevalentintheworld’spopulationssincenoeffectivetreatmentsareavailabletoeradicatethem. e 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.Duetothesereasons,thereisaneedtoseekanddevelopnoveltherapeuticregimenstoreducetherapidscaleofbacterial infections. Antimicrobial Peptides (AMPs) are components of the first line of defense for prokaryotes and eukaryotes and have a widerangeofactivitiesagainstGram-negativeandGram-positivebacteria,fungi,cancercells,andprotozoa,aswellasviruses.In thisstudy,peptideswhichwereinitiallyidentifiedfortheirHIVinhibitoryactivitywerefurtherscreenedforantibacterialactivity throughdeterminationoftheirkineticsaswellastheircytotoxicity.Fromtheresultsobtained,theMICsoftwoAMPs(Molecule3 and Molecule 7) were 12.5 μg/ml for K. pneumoniae (ATCC 700603) and 6.25 μg/ml for P. aeruginosa (ATCC 22108). e two AMPskilledthesebacteriarapidly in vitro,preventingbacterialgrowthwithinfewhoursoftreatment.Furthermore,thecytotoxic activity of these two peptides was significantly low, even at an AMP concentration of 100 μg/ml. ese 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. 1. Introduction e human body is equipped with a defence mechanism, which enables it to eradicate foreign bodies and/or patho- genic organisms [1, 2]. However, the inability of the human defence system to defend itself following a microbial in- vasion of the immune system will ultimately result in complete immunity breakdown, hence giving way for the entrance of other pathogenic organisms into the body. Whilemostbacteriacohabitatewithhumancellswithout causing any harm and disruption, some common infectious pathogens that would cause diseases may include the Methicillin-resistant Staphylococcus aureus (MRSA) strains, Candida albicans, Herpes simplex, Mycobacterium avium complex (MAC), Mycobacterium tuberculosis, Klebsiella pneumoniae, and Pseudomonas aeruginosa, just to name a few [3]. S. aureus, K. pneumoniae, E. coli,and P. aeruginosa are examples of bacteria that have serious clinical and medical implications in individuals, and these bacteria ac- count for the major causes of nosocomial infections worldwide [4, 5]. In addition, these pathogenic microbes have been cited as the major causative agents for many infectionssuchasskininfections,respiratoryinfections,and othermajorillnesses.Insomeinstances,theseinfectionscan lead to life-threatening diseases such as pneumonia, men- ingitis, toxic shock syndrome, and bacteremia [5–7]. Hindawi International Journal of Microbiology Volume 2020, Article ID 2131535, 9 pages https://doi.org/10.1155/2020/2131535