Investigation of bioactive components responsible for the antibacterial and anti-biofilm activities of Caroxylon volkensii by LC-QTOF-MS/MS analysis and molecular docking.

Caroxylon volkensii is a wild desert plant of the family Amaranthaceae. This study represents the first report of the metabolomic profiling of C. volkensii by liquid chromatography quadrupole-time-of-flight tandem mass spectrometry (LC-QTOF-MS/MS). The dereplication study of its secondary metabolites led to the characterization of 66 known compounds. These compounds include catecholamines, tyramine derivatives, phenolic acids, triterpenoids, flavonoids, and others. A new tyramine derivative, alongside other known compounds, was reported for the first time in the Amaranthaceae family. The new derivative and the first-reported compounds were putatively identified through MS/MS fragmentation data. Given the notorious taxonomical challenges within the genus Salsola, to which C. volkensii previously belonged, our study could offer a valuable insight into its chemical fingerprint and phylogenetic relationship to different Salsola species. The antibacterial potential of C. volkensii methanolic extract (CVM) against Pseudomonas aeruginosa was screened. The minimum inhibitory concentration (MIC) of CVM ranged from 32 to 256 µg mL-1. The anti-quorum sensing potential of CVM resulted in a decrease in the percentage of strong and moderate biofilm-forming isolates from 47.83% to 17.39%. It revealed a concentration-dependent inhibitory activity on violacein formation by Chromobacterium violaceum. Moreover, CVM exhibited an in vivo protective potential against the killing capacity of P. aeruginosa isolates. A molecular docking study revealed that the quorum-sensing inhibitory effect of CVM can be attributed to the binding of tyramine conjugates, ethyl-p-digallate, and isorhamnetin to the transcriptional global activator LasR.

Differential Impact of Specific Amino Acid Residues on the Characteristics of Avian Influenza Viruses in Mammalian Systems.

Avian influenza virus (AIV) H9N2 was declared to be endemic in birds of the Middle East, in particular in Egypt, with multiple cases of human infections. Despite concerns about the pandemic threat posed by H9N2 AIV, due to the fact that its receptor specificity is similar to that of human influenza viruses, its morbidity and mortality rates in humans are so far negligible. However, the acquisition of specific adaptive amino acid (aa) mutations in the viral polymerase can enhance cross-species transmission of the virus itself or of reassortants, which gained these changes. The polymerase basic protein 2 (PB2) is one of the key determinants for AIV adaptation towards mammals. Although mammalian pathogenicity-related mutations (MPMs) in PB2 genes were identified in different AIVs, the specific effect of single or multiple mutations on viral fitness has not been compared so far. Here, we studied the effect of the aa K at position 591, which was frequently reported in the PB2 of Egyptian H9N2 isolates, on the proliferation efficiency and polymerase activity of an H5N1 (clade 2.2.1.2) AIV already carrying the mammalian adaptive mutation 627K. Using reverse genetics, we generated a set of recombinant parental strains and H5N1 variants carrying the avian-like 591Q/627E or mammalian-like adaptive mutations 591K/627K (H5N1EGY, H9N2EGY, H5N1PB2-H9N2EGY, H5N1H9N2_PB2_K591Q, H5N1PB2_K627E, H5N1PB2_K627E/591K, H5N1PB2_627K/591K). Regardless of the avian-like 627E or the mammalian-adaptive 627K, both variants carrying the 591K (H5N1PB2_K627E/591K, H5N1PB2_627K/591K) and the reassortant H5N1PB2-H9N2EGY replicated to significantly higher levels in mammalian continuous MDCK and Calu-3 cell lines and primary normal human bronchial epithelial cells than the parental H5N1EGY virus (carrying solely the 627K adaptive mutation). Expectedly, the H5N1 variants carrying avian-like PB2 mutations (H5N1H9N2_PB2_K591Q, H5N1PB2_K627E) replicated to significantly lower levels than the parental H5N1EGY virus in the predefined primary and continuous mammalian cell line systems. Consistently, the activity of H5N1 subtype AIV polymerase complexes comprising PB2 segments with singular 591K or combined with 627K was significantly enhanced when compared to parental H5N1EGY and H9N2EGY. This study emphasizes the significant impact of 591K containing PB2 segments in the background of H5N1 polymerase on viral fitness in addition to the well-known MPM 627K in vitro.

Histological assessment, anti-quorum sensing, and anti-biofilm activities of Dioon spinulosum extract: in vitro and in vivo approach.

Pseudomonas aeruginosa is an opportunistic bacterium causing several health problems and having many virulence factors like biofilm formation on different surfaces. There is a significant need to develop new antimicrobials due to the spreading resistance to the commonly used antibiotics, partly attributed to biofilm formation. Consequently, this study aimed to investigate the anti-biofilm and anti-quorum sensing activities of Dioon spinulosum, Dyer Ex Eichler extract (DSE), against Pseudomonas aeruginosa clinical isolates. DSE exhibited a reduction in the biofilm formation by P. aeruginosa isolates both in vitro and in vivo rat models. It also resulted in a decrease in cell surface hydrophobicity and exopolysaccharide quantity of P. aeruginosa isolates. Both bright field and scanning electron microscopes provided evidence for the inhibiting ability of DSE on biofilm formation. Moreover, it reduced violacein production by Chromobacterium violaceum (ATCC 12,472). It decreased the relative expression of 4 quorum sensing genes (lasI, lasR, rhlI, rhlR) and the biofilm gene (ndvB) using qRT-PCR. Furthermore, DSE presented a cytotoxic activity with IC50 of 4.36 ± 0.52 µg/ml against human skin fibroblast cell lines. For the first time, this study reports that DSE is a promising resource of anti-biofilm and anti-quorum sensing agents.

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

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.