Antimicrobial Effects of Ethanol Extracts from Uncaria tomentosa, Haematoxylum brasiletto, and Cymbopogon citratus on Multidrug-Resistant Clinical Strains
Background: Antimicrobial resistance represents one of the most significant threats to global health and development. According to the World Health Organization (WHO), bacterial resistance was directly responsible for 1.27 million deaths worldwide in 2019. Consequently, the pharmaceutical industry has renewed its interest in natural products and their potential application in the search for more effective drugs to combat human diseases. This study aimed to determine the antimicrobial activity of three ethanolic plant extracts—Brazilwood (Haematoxylum brasiletto), cat's claw (Uncaria tomentosa), and lemongrass (Cymbopogon citratus)—against multidrug-resistant bacteria. Methods: Biological activity was determined following the M26-A protocol of the Clinical and Laboratory Standards Institute (CLSI). Results: Growth inhibition was observed for H. brasiletto (50 mg/mL) against Gram-positive bacteria, such as S. aureus ATCC BAA-44, using agar diffusion and microdilution methods, with a minimum inhibitory concentration (MIC) of 6.25 mg/mL and an inhibition zone of 31 mm in diameter. Similarly, P. aeruginosa 27853, E. faecalis 29212, and A. baumannii 27853 showed inhibition at concentrations of 12.5 mg/mL and 6.25 mg/mL, respectively, with inhibition zone diameters of 12 mm, 21 mm, and 16 mm, respectively. U. tomentosa exhibited bacteriostatic activity, reducing the bacterial population to a few typical pathogen colonies at a concentration of 200 mg/mL. C. citratus did not demonstrate bactericidal or bacteriostatic activity against the bacteria under study. Antimicrobial susceptibility testing performed on reference strains (ATCC) revealed resistance to most antibiotics but susceptibility to ciprofloxacin. Conclusion: Based on the results obtained, medicinal plant extracts are recommended as alternatives for treatment and/or as adjuvants for infectious diseases caused by multidrug-resistant strains.
Keywords: Multidrug-resistant, Plant extract, Antibacterial potential.
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