Antimicrobial activity and potential of olive leaf extract as a topical agent to combat staphylococcus aureus and MRSA strains: an in vitro evaluation

Abstract

Staphylococcus aureus is one of the most prevalent bacteria in skin and soft tissue infections (SSTIs). Multidrug-resistant strain emergence, particularly methicillin-resistant S. aureus (MRSA), highlights the need for alternative treatments. Objectives: This study investigates the antimicrobial properties of olive leaf extract (OLE) and describes an epidemiological profiling of patients with SSTI who may benefit from it. Methods: OLE was tested in two reference strains, methicillin-susceptible S. aureus (MSSA) ATCC 29213 and MRSA ATCC 700699, and in 126 clinical isolates from patients with SSTIs according to Clinical Laboratory Standards Institute guidelines. Results: The minimum bactericidal concentration (MBC) ranged from 3.12% to 6.25% w/v for MSSA and 1.56% to 3.12% for MRSA. The lethal curve showed a reduction of 6 log10CFU/mL after two hours of incubation. Most of the 126 clinical samples (103 MSSA and 23 MRSA) came from skin lesions, surgical wounds, and ulcers. Over 90% of MSSA strains were resistant to less than five antibiotics, while 82% of MRSA strains were resistant to more than six. Penicillins demonstrated the lowest susceptibility rate (19.8%), whereas linezolid, daptomycin, pristinamycin, trimethoprim–sulfamethoxazole, teicoplanin, vancomycin, and OLE exhibited 100% susceptibility. No growth was observed for all clinical strains with OLE at ≥6.25% w/v. Conclusions: The findings suggest that OLE could become a promising alternative treatment for skin infections, particularly in the context of increasing antibiotic resistance.

Laura Clusa holds a postdoctoral contract from Plan de Recuperación, Transformación y Resiliencia (Instituto de Salud Carlos III, Ministerio de Ciencia, Innovación y Universidades) from Unión Europea-NextGeneration EU, grant number Sara Borrell CD22/00152. This research was funded by Ministerio de Ciencia e Innovación-Fondo Europeo de Desarrollo Regional, grant number PID2022-136414OB-I00, the Spanish Ministry of Science and Innovation, with funds from the European Union NextGeneration EU Recovery, Transformation and Resilience Plan, grant number PRTR-C17.I1, Interreg Sudoe Program, grant number NEWPOWER, S1/1.1/E01116, CIBER Fisiopatología de la Obesidad y la Nutrición as an initiative of FEDER-ICCIII, grant number CIBEROBN, CB06/03/1012, and Fondo Social Europeo-Gobierno de Aragón, grant number research groups: B10_23R, B16_23R, and B59_23D.