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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.

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Biologia Futura
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.

Open access
Acta Biologica Hungarica
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.

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Helyi érzéstelenítők antibakteriális hatása

Antibacterial effect of local anaesthetics

Orvosi Hetilap
Authors: Zoltán Szabó, Éva Szentkirályi, Tamás Kovács, Örs Győrffy, Balázs Sütő, István Bátai, and Monika Kerényi

Összefoglaló. Gyógyszereink egy részének jelentős, az eredeti alkalmazástól eltérő hatása is van. Ezek felismerése fontos, hogy elkerüljük a nem várt mellékhatásokat, vagy kihasználjuk ezeket a kedvező adottságokat. A helyi érzéstelenítők antibakteriális hatása 1909 óta ismert, de ennek több évtizeden keresztül nem tulajdonítottak jelentőséget. Az 1960-as években figyeltek fel először az álnegatív mikrobiológiai eredmények lehetőségére, helyi érzéstelenítőket használva a mintavételhez. Tanulmányok igazolták, hogy a bronchoszkópiás, seb-, bőr- vagy fül-, orr-, gégészeti bakteriológiai eredmények is érintve lehetnek. A ma is használt gyógyszerek közül a 0,5%-os bupivakainnak és a 2%-os lidokainnak van jelentős antibakteriális hatása Gram-pozitív és Gram-negatív baktériumokkal szemben, ami kifejezettebb 37 °C-on, mint szobahőmérsékleten. A legerősebb antibakteriális hatást a 0,5%-os bupivakain mutatta. A napi gyakorlatban alkalmazott koncentrációjuk magasabb, mint a különböző klinikai izolátumokkal szemben meghatározott minimális gátló koncentráció. Fenti tulajdonságaik alapján felmerült szerepük a kórházi sebfertőzések csökkentésében is. A hatásmechanizmus több pontja ismert, károsítják a sejthártya integritását, és több bakteriális enzim működését gátolják. Orv Hetil. 2021; 162(5): 171–176.

Summary. Medications may have important impacts other than the original effect. It is important to know about these to avoid side effects or use these beneficial capabilities. The antibacterial effect of local anaesthetics has been known since 1909. For decades, no attention has been payed to this fact. In the 1960s, the high number of negative microbiological results when local anaesthetics were used before sampling drew attention to the possible antibacterial effect. Studies suggested that cultures from bronchoscopy, wound, skin or nasal samples may be affected. Bupivacaine 0,5% and lidocaine 2% have the most noticeable effect against both Gram-positive and Gram-negative bacteria. This impact is more pronounced at 37 °C than at room temperature. Bupivacaine 0,5% has the most pronounced effect. The concentration of local anaesthetics in daily routine is higher than the minimal inhibitory concentration against various clinical isolates. In the view of these results, they may contribute to reduce surgical site infections. There are known details regarding the mechanism of action. Local anaesthetics have target sites on cellular membrane and inhibit bacterial enzymes. Orv Hetil. 2021; 162(5): 171–176.

Open access
Acta Microbiologica et Immunologica Hungarica
Authors: Balazs Ittzes, Eva Szentkiralyi, Zoltan Szabo, Istvan Z. Batai, Ors Gyorffy, Tamas Kovacs, Istvan Batai, and Monika Kerenyi


Infection is one of the most feared hospital-acquired complications. Infusion therapy is frequently administered through a central line. Infusions facilitating bacterial growth may be a source of central line-associated bloodstream infections. On the other hand, medications that kill bacteria may protect against this kind of infection and may be used as a catheter lock.

In this study, we examined the impact of amiodarone on bacterial growth. Amiodarone is used for controlling cardiac arrhythmias and can be administered as an infusion for weeks. Standard microbiological methods have been used to study the growth of laboratory strains and clinical isolates of Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and multidrug-resistant Acinetobacter baumannii in amiodarone. The minimum inhibitory concentration (MIC) of amiodarone was determined. Bacterial growth from in use amiodarone syringes and giving sets was also investigated.

Most examined strains were killed within 1 min in amiodarone. The other strains were killed within 1 h. The MICs of amiodarone were <0.5–32 μg/mL.

Amiodarone infusion is unlikely to be responsible for bloodstream infections as contaminating bacteria are killed within 1 h. Amiodarone may also protect against central line infections if used as a catheter lock.

Open access