טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentAyeletsarah Hershkovits
SubjectTargeting Staphylococcus Aureus Virulence using a
Membrane-Active lipopeptide
DepartmentDepartment of Biotechnology and Food Engineering
Supervisor Full Professor Mor Amram
Full Thesis textFull thesis text - English Version


Abstract

The rapid evolution and distribution of multi-drug resistant bacteria combined with failure in antibacterial drug discovery, is a global health crisis. Specifically, Staphylococcus aureus is a major human pathogen capable of a wide range of severe infections and disease such as skin, soft tissue and bloodstream infections. Furthermore, S. aureus has an extensive arsenal of antibiotic resistance and virulence factors making the bacteria highly pathogenic. These factors enable bacteria to evade both conventional antibacterial agents and the innate immune system, resulting in poor resolution of bacterial infections. Membrane active compounds are considered attractive candidates as new antibacterial agents due to their non-specific mode of action. By targeting multiple bacterial membrane functions, they exert less selective pressure, potentially bypassing acquired bacterial resistance. Specifically, the peptidomimetic family of acyl-cation oligomers was studied for its ability to encompass antimicrobial properties similar to host defense peptides, an essential part of the innate immune system. Here, the antibacterial effects of C10OOC12O (i.e. decanoyl-ornithyl-ornithyl-dodecanoyl-ornithyl-amide), a representative of this peptidomimetic family were assessed. The antibacterial activity of C10OOC12O was determined against representative Gram-positive bacterial strains and was found be mildly active with a bacteriostatic mode of action, namely against a clinically relevant multi-drug resistant S. aureus strain USA300. The peptidomimetic has caused mild membrane damage, resulting in inhibition of an important antibiotic resistance factor thereby re-sensitizing the MRSA to several antibiotics. Furthermore, at sub-inhibitory concentrations the membrane damage resulted in inhibition of a reporter enzyme of a regulatory system responsible for the expression of many virulence factors. The therapeutic potential was investigated by testing the activity in a complex medium (i.e. human plasma). C10OOC12O retained its activity and even elicited the antibacterial activity of plasma proteins. Moreover, in-vivo efficacy was also demonstrated using the murine peritonitis sepsis model, achieving a 60% survival. Collectively, these findings suggest a potentially attractive anti-virulence strategy sensitizing bacteria to the hosts immune system at sub-inhibitory concentrations.