Authors:Zoltán Varga, Mira Szabó, Monika Kerényi and Joseph Molnár
Antibiotics are usually studied on pure cultures of a single bacterial strain, whereas multi-species communities that inhabit human niches and the biosphere are generally ignored. The modification of quorum sensing (QS) is investigated in a system involving a co-existing signal producer and sensor bacterial cells. A pure culture of merely one bacterial species is quite rare in any niche. The interactions of different bacterial species may therefore be of special importance in pathogenicity, antibiotic resistance and signal transmission.In the present study the authors investigated the QS in model experiments involving several Gram-positive and Gram-negative bacterial species isolated from human infections or laboratory strains. The effects of various compounds on QS were studied in mixed bacterial populations during the incubation period of 24–48 h. As the simplest example of co-existing cell populations, the N-acyl homoserine lactone producing Ezf 10–17 was applied with Chromobacterium violaceum 026 as sensor.The signal of QS transmission between the co-existing QS system and pathogenic bacteria isolated from various patients was found to be modified by certain bacterial cells. The bacterial-bacterial interactions in a mixed flora can change the classical signal transmission in the microbial community and should therefore be taken into consideration in rational chemotherapy.
Authors:Tünde Dénes, Sámuel Gergely Bartha, Mónika Kerényi, Erzsébet Varga, Viktória Lilla Balázs, Rita Csepregi and Nóra Papp
In this study field restharrow (Ononis arvensis) was investigated for histological and antimicrobial features. The aerial part and the root were embedded in synthetic resin and investigated following sectioning by a rotation microtome. The antimicrobial activity and minimum inhibitory concentration of the solvent fractions of the aerial part were studied against four bacterial strains and one fungus. According to histology, the root covered by rhizodermis contains contiguous vascular elements, which are surrounded by sclerenchyma cells. The epidermis cells are anisodiametric in the stem, sepal, and petal. The bundles of the stem form a Ricinus type thickening. The adaxial side of the heterogeneous leaf is covered by unbranching non-glandular and capitate glandular trichomes. The stipule, petiole, sepals and petals are isolateral having mesomorphic stomata. Pollen grains are tricolpate. The different extracts of the herb showed antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Salmonella Typhimurium, Staphylococcus aureus, and Candida albicans. Data show that the extracts of the leaf contain compounds which may be responsible for the antifungal effect, while extracts obtained from display against the tested bacteria, except Escherichia coli. Further studies are required to complete the phytochemical analysis and identify the antimicrobial compounds of extracts.
Authors:Gergely Sámuel Bartha, Gergő Tóth, Péter Horváth, Eszter Kiss, Nóra Papp and Monika Kerényi
Several Aristolochia species were used as medicinal herb across Europe and in recent years, their antimicrobial activity has also been investigated.
Materials and methods
In this study, A. clematitis was selected to evaluate the aristolochic acids I and II (AA I and AA II) concentrations and the antimicrobial activity of methanol, hexane, butanol, and ethyl acetate extracts of the root, stem, leaf, root, and fruit. AA I and AA II contents were measured by a validated high-performance liquid chromatography–ultraviolet method.
Each fraction of the plant contained AA I and AA II and the root was found to have the highest contents of AA I (1.09%) and AA II (0.7454%). The minimum inhibitory concentrations of all extracts were determined by standard microdilution method. The fruit’s extracts showed the most efficient antimicrobial effect against both methicillin sensitive and resistant Staphylococcus aureus strains.
Correlation between the AA I and AA II concentrations and the antimicrobial effect was not found.