Investigation of the Antibacterial Activity and Efflux Pump Inhibitory Effect of Cycas thouarsii R.Br. Extract against Klebsiella pneumoniae Clinical Isolates

Abstract

The vast spread of multidrug-resistant bacteria has encouraged researchers to explore new antimicrobial compounds. This study aimed to investigate the phytochemistry and antibacterial activity of Cycas thouarsii R.Br. leaves extract against Klebsiella pneumoniae clinical isolates. The minimum inhibitory concentration (MIC) values of C. thouarsii extract ranged from 4 to 32 µg/mL. The impact of the treatment of the isolates with sub-inhibitory concentrations of C. thouarsii extract was investigated on the bacterial growth, membrane integrity, inner and outer membrane permeability, membrane depolarization, and bacterial morphology using a scanning electron microscope (SEM) and on the efflux activity using qRT-PCR. Interestingly, most K. pneumoniae isolates treated with C. thouarsii extract showed growth inhibition—a decrease in membrane integrity. In addition, we observed various morphological changes, a significant increase in inner and outer membrane permeability, a non-significant change in membrane depolarization, and a decrease in efflux activity after treatment. The phytochemical investigation of C. thouarsii extract revealed the isolation of one new biflavonoid, 5,7,7”,4”’-tetra-O-methyl-hinokiflavone (3), and five known compounds, stigmasterol (1), naringenin (2), 2,3-dihydrobilobetin (4), 4’,4’’’-O-dimethyl amentoflavone (5), and hinokiflavone (6), for the first time. Moreover, the pure compounds’ MICs’ ranged from 0.25 to 2 µg/mL. Thus, C. thouarsii could be a potential source for new antimicrobials.

Antimicrobial Activity of Brassica rapa L. Flowers Extract on Gastrointestinal Tract Infections and Antiulcer Potential Against Indomethacin-Induced Gastric Ulcer in Rats Supported by Metabolomics Profiling

“…If the inner membrane permeability increases, ONPG enters the bacterial cells and is converted by β-galactosidase, which is present in the bacterial cytoplasm, into O -nitrophenol (ONP). 24 ONP has a yellow color, and its amount can be detected by measuring the absorbance at OD = 420 over time. An illustrative example is shown in Figure 4B .…”

“…Inner membrane permeability was assessed in the tested isolates using ONPG as a substrate to detect the cytoplasmic activity of the enzyme β-galactosidase. 24 Bacterial isolates were overnight grown in Mueller–Hinton broth (MHB) supplemented with 2% lactose and then centrifuged. After washing the pellets, they were resuspended in 0.5% NaCl.…”

Elucidation of the Metabolite Profile of Yucca gigantea and Assessment of Its Cytotoxic, Antimicrobial, and Anti-Inflammatory Activities

“…Using the agar well diffusion method, the antimicrobial activity of YGME extract was evaluated [24,25]. The tested bacterial and fungal species were Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 13883), Pseudomonas aeruginosa (ATCC 27853), Proteus mirabilis (ATCC 35659), Salmonella typhimurium (ATCC 14028) as Gram-negative bacteria.…”

In Vivo and In Vitro Antimicrobial Activity of Biogenic Silver Nanoparticles against Staphylococcus aureus Clinical Isolates

“…The effect of the green-synthesized AgNPs on the integrity of the cell membrane of the tested isolates was studied by monitoring the release of materials that have absorbance at 260 nm (A260) [54]. In brief, the optical density (OD) of the overnight bacterial cultures in nutrient broth was adjusted to be 0.4 at 630 nm.…”