Antimicrobial activities of some Verbascum L. species against clinical isolates of Klebsiella pneumoniae causing lower respiratory tract infections

Increasing antibiotic resistance in Klebsiella pneumoniae has necessitated the development of novel antimicrobial therapies. In recent years, many studies have been conducted on using plants as antimicrobial agents, and many natural compounds have been found to be effective sources of antibacterial agents. In the present study, the antimicrobial activity of K. pneumoniae strains isolated from patients with lower respiratory tract infections (LRTIs) was investigated against some Verbascum L. species. Five K. pneumoniae strains, isolated from bronchoalveolar lavage (BAL) samples of patients with LRTIs, were identified by VITEK MS MALDI-TOF (BioMerieux, France). Then, the antimicrobial activity of 85% ethanol and 2% aqueous extracts of nine Verbascum species (V. ancyritanum Bornm., V. cheiranthifolium Boiss., V. georgicum Benth., V. kastamunicum Murb., V. lasianthum Boiss. ex Benth., V. mucronatum Lam., V. sinuatum L. subsp. sinuatum var. adenosepalum Murb., V. speciosum Schrad., V. uschakense Hub.-Mor.), three of which are endemic to Turkish flora, was investigated by using the microdilution method. Both 85% ethanol and 2% aqueous extracts of Verbascum species showed MIC values between 128 - 256 ƒÊg/mL and MBC in the range of 256 - 1024 ƒÊg/mL. The endemic species, V. ancyritanum presented the most effective antimicrobial activity. In the present study, the antimicrobial activity of endemic species, V. ancyritanum, V. kastamunicum, and V. uschakense, was investigated for the first time. All extracts were found to have moderate antimicrobial activity against the studied bacteria.