Perspectives on the fighting against Acinetobacter baumannii via plants as promising weapons against multidrug-resistant bacteria: a systematic review

Objectives and aims: Multi-drug resistant (MDR) Acinetobacter baumannii is a prominent cause of various nosocomial infections including ventilator-associated pneumonia, bacteremia, meningitis, urinary tract infections, and wound infections. Therefore, finding new compounds or therapeutic approaches to overcome this pathogen is necessary. This review systematically investigated the effects of herbal components with antibacterial and anti-biofilm activities against standard and clinical isolates of A. baumannii. Methods: A search was conducted on four prominent academic databases, namely Web of Sciences, PubMed, Medline, and Scopus databases, for articles published by March 18, 2023. The research followed the seven procedures outlined in the Cochrane Handbook. Multiple keywords were used to search for papers, including 'A. baumannii' in combination with 'herbal medicine' or p'lant compound', as well as 'biofilm' or 'antibacterial' or 'antimicrobial'. Results: Overall, 29 articles that considered the effects of 133 plant species on A. baumannii were reviewed. The studies used micro/macro-broth dilution method and/or agar well/disk diffusion assay to assess the antimicrobial properties of herbal derived compounds. Several compounds had significant antibacterial and bactericidal effects against multi-drug resistant bacterium, A. baumannii, even better than common antibiotics. Moreover, some of these active compounds presented anti-biofilm effect by either preventing formation or dispersing A. baumannii biofilms, and disrupting the quorum-sensing (QS) system. Conclusion: Based on the results, essential oils (EOs) of Myrtus communis, Ziziphora tenuior, Pimenta dioica and Pimenta racemose, Eucalyptus camaldulensis, Origanum vulgare, and Mentha pulegium as well as linalool displayed promising effects against A. baumannii. However, further mechanistic, toxicological, and in vivo investigations are necessary to confirm their clinical efficacy.