Thesis (Ph.D.) - Cairo University - Faculty of Pharmacy - Department of Microbiology and Immunology

Lysostaphin (LST) is an extracellular zinc metalloproteinase bacteriocin secreted by Staphylococcus simulans biovar staphylolyticus that destroys staphylococcal cell wall through its endopeptidase activity. S. aureus imposes a threatening public health issue;hence, interest is raised back in LST.However, its usage is limited due to the lack of affordable, highly-active preparations. Herein the main objective was directed towards achieving sustainable and low-cost LST production platform, using both recombinant and native lysostaphin,to be used in combating S.aureus infections. Recombinant DNA technology was used to clone, express, and purify LST as an N-terminal His-tagged protein in Escherichia coli. A full factorial design was developed in which induction was optimized, being reflected in minimal cost and time. The produced rLST was evaluated in combating biofilms using crystal-violet based assays. This work was further expanded by aiming to develop a novel rLST topical formula targeting staphylococcal skin infections and assessing it in a murine skin model of infection. The rLST optimized production process yielded up to 50 mg/L culture, which is higher than previously reported systems.The purified rLST demonstrated superlative activity in inhibiting staphylococcal biofilms formation as well as detachment of previously established ones, compared to vancomycin and linezolid. Finally, phase inversion composition (PIC) method was successful in incorporating LST in a nano-emulgel (LNEG) which was able to extend active LST release up to 8 h and cure skin infections in a murine skin model

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