Alex Huynh Dalraj Dhillon Dhairya Bhatt Eric Zhang


Introduction: Endolysins, antimicrobial peptides that disrupt the peptidoglycan (PG) layer of bacteria, are a strong alternative to common antibiotics and less prone to antibiotic resistance. However, endolysins are ineffective against gram-negative bacteria due to an additional outer membrane (OM) blocking the PG layer. This research protocol aims to address this caveat by developing a novel recombinant endolysin peptide, EndoT5-Ctn (15-34), comprised of phage Endolysin T5 and a Crotalicidin tag (Ctn (15-34)) capable of permeabilizing the OM. This would render the endolysin effective against gram-negative bacteria such as multidrug-resistant (MDR) Pseudomonas aeruginosa.

Methods: Experimentation will begin with recombinant DNA techniques to engineer a bacterial vector which expresses the EndoT5-Ctn (15-34) peptide. Protein expression will be achieved in competent BL21 (DE3) E. coli strains before protein isolation with lysis methods and immobilized-metal affinity chromatography. Resulting sample concentrations will be assayed using spectrophotometry. Finally, in vivo minimal inhibitory and bactericidal concentration assays will be conducted on MDR P. aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) to evaluate bactericidal efficacy.

Results: A minimal bactericidal concentration of EndoT5-Ctn (15-34) recombinant endolysin is expected to yield significant bactericidal activity against the MDR P. aeruginosa strain with limited effect on the gram-positive MRSA. A higher concentration of recombinant endolysin is expected to maintain its gram-negative bactericidal efficacy with an imported grampositive bactericidal efficacy.

Discussion: The observed bactericidal efficacy on AMR and non-AMR strains on P. aeruginosa will prompt further exploration of the therapeutic feasibility of this therapy regarding factors such as cytotoxicity, immunogenicity, and thermal stability. The potential introduction of recombinant endolysins presents an alternative treatment for infections with reduced risk of inducing resistant mutations.

Conclusion: The EndoT5-Ctn (15-34) recombinant endolysin is a novel anti-bacterial agent which is expected to have significant bactericidal effects on MDR strains of gram-negative bacteria which current antibiotics have been ineffective at combating.

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Research Protocol