In recent years, antibiotic resistance has become more sophisticated, putting mankind into the postantibiotic era. Many clinical Enterobacteriaceae strains such as Escherichia coli and Klebsiella pneumoniae have extended-spectrum beta-lactamase (ESBL) and carbapenem-resistant Enterobacteriaceae (CRE) [1–3]. Polymyxin plasmid-mediated resistance gene (mcr-1) especially was observed in E. coli strains, which was isolated from animals and in patients with infection during 2011–2014, in China . Moreover, it is with profound concern that mcr-1 could be transferred to K. pneumoniae and Pseudomonas aeruginosa via transformation . In 2016, the first report about mcr-1 gene in a patient with urinary tract infections (UTIs) in Pennsylvania, the United States, was shown by Abbasi . According to recent reports, the causative agents of UTIs include uropathogenic E. coli, Klebsiella pneumoniae, Enterococcus spp., Staphylococcus saprophyticus, group B Streptococcus (GBS), Proteus mirabilis, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida spp. [6–10], in which Escherichia coli is the most common causative agents of both uncomplicated and complicated UTIs .
Herbal extracts and essential oils were used as foods such as floral beverages, functional foods, and traditional medicines in many years, with minimal known “side effects” on human health. Using herbal remedies might help in reducing dependence on antibiotic therapies and minimizing antibiotic resistance .
The Asteraceae family (Compositae) is a widespread family of flowering plants, including 32,913 species names, belonging to 1,911 plant genera, distributed in 13 subfamilies . The tropics, subtropics, and temperate regions are the natural habitats of Asteraceae species . They usually contain a large amount of essential oil, polyphenols, and flavonoid compounds, which are often studied for antimicrobial and antioxidant activities [14–19].
Although there were many reports for antimicrobial and antioxidant effects of Asteraceae species, applications of these extracts in treating infectious diseases need an evaluation of pathogenic bacterial strains isolated from clinical specimens . In the study, we screened antimicrobial and antioxidant activities of ethanol extracts and essential oils from nine species of Asteraceae on 30 clinical strains causing urinary tract infection, collected from District 2 Hospital, Ho Chi Minh City, Vietnam. The target was seeking the best extract to apply for a healthcare serum to prevent recurrent UTIs. The antioxidant activity might be a protective factor for urinary tract epithelium to avoid the impact of oxidative stress.
Antioxidant and antimicrobial activities were determined by standard protocols. Essential oils from Ageratum conyzoides, Helianthus annuus, and Artemisia vulgaris indicated significant inhibitory effects on Staphylococcus aureus and Candida spp. Crude extracts and fractions from Taraxacum officinale, Chrysanthemum morifolium, A. conyzoides, and Tagetes erecta showed inhibitory ability on at least one testing bacterial strains including S. aureus, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. In a study on clinical isolates, ethyl acetate fraction from A. conyzoides flower displayed the most potent effect on uropathogenic E. coli and K. pneumoniae with MIC at 1.25–10 mg/ml and 5–12.5 mg/ml, respectively. DPPH-scavenging assay indicated that T. erecta extract had the lowest IC50 (17.280 μg/ml) and is 2.4 times higher than vitamin C (7.321 μg/ml). This study revealed that A. conyzoides has good potential against uropathogenic E. coli and K. pneumoniae, and therefore could be applied for prophylactic treatment of urinary infection.
Citation: Trinh, Phan-Canh, Le-Thi-Thanh Thao, Hoang-Tran-Viet Ha, and TuAnh Nguyen. “DPPH-scavenging and antimicrobial activities of Asteraceae medicinal plants on uropathogenic bacteria.” Evidence-Based Complementary and Alternative Medicine 2020 (2020).