Zsuzsanna Schelz

Bio: Zsuzsanna Schelz is an academic researcher from University of Szeged. The author has contributed to research in topics: Chemistry & Medicine. The author has an hindex of 12, co-authored 20 publications receiving 966 citations.

Inhibition of quorum-sensing signals by essential oils

Abstract: The role of quorum sensing (QS) is well known in microbial pathogenicity and antibiotic resistance. QS is responsible for motility, swarming, and biofilm production based on the signal molecules, e.g., acylated homoserine lactones (AHLs) produced by micro-organisms above certain population density. The inhibition of QS may reduce pathogenicity, antibiotic resistance and biofilm formation in systemic and local infections. The homoserine lactones and other transmitters contribute to antibiotic resistance and pathogenicity of several bacteria; consequently the inhibition of QS signals reduces the problem of resistance and virulence. Due to the increasing number of persistent non-treatable infections, there is an urgent need to develop new strategies to combat infections that destabilize bacterial communities in the host. The effect of essential oils on bacterial growth and QS were evaluated using the sensor strain Chromobacterium violaceum CV026 and N-acyl homoserine lactone (AHL) producing Escherichia coli ATTC 31298 and the grapevine colonizing Ezf 10-17 strains. Of the tested oils, rose, geranium, lavender and rosemary oils were the most potent QS inhibitors. Eucalyptus and citrus oils moderately reduced pigment production by CV026, whereas the chamomile, orange and juniper oils were ineffective.

The Mechanism of Plasmid Curing in Bacteria

Abstract: Bacterial plasmids have a major impact on metabolic function. Lactose fermentation of E. coli or hemolysin B transporter expressed by the plasmids that carry these respective genes could be readily obviated by heterocyclic compounds that readily bind to plasmid DNA. These compounds could also reverse the resistance to antibiotics of E. coli , Enterobacter, Proteus, Staphylococcus and Yersinia strains by eliminating plasmids. However, the frequency and extent of this effect was significantly less than might have been expected based on a complex interaction with plasmid DNA. The effects of heterocyclic compounds on the plasmids responsible for the virulence of Yersinia and A. tumefaciens, or on nodulation, nitrogen fixation of Rhizobia accounted for the elimination of 0.1 to 1.0 % of plasmids present in the populations studied. Bacterial plasmids can be eliminated from bacterial species grown as pure or mixed bacterial cultures in the presence of sub-inhibitory concentrations of non-mutagenic heterocyclic compounds. The antiplasmid action of the compounds depends on the chemical structure of amphiphillic compounds having a planar ring system with substitution in the L-molecular region. A symmetrical π-electron conjugation at the highest occupied molecular orbitals favours the antiplasmid effect. The antiplasmid effect of heterocyclic compounds is expressed differentially in accordance with the structural form of the DNA to which they bind. In this manner extrachromosomal plasmid DNA that exists in a superhelical state binds more compound than its linear or open-circular form; and least to the chromosomal DNA of the bacterium, that carries the plasmid. It can also be noted that these compounds are not mutagenic and their antiplasmid effects correlate with the energy of HOMO-orbitals. Plasmid elimination is considered also to take place in ecosystems containing numerous bacterial species. This opens up a new perspective in rational drug design against bacterial plasmids. The inhibition of conjugational transfer of antibiotic resistance plasmid can be exploited to reduce the spread of antibiotic resistance plasmid in the ecosystem. Inhibition of plasmid replication at various stages, as shown in the rolling circle model (replication, partition, conjugal transfer) may also be the theoretical basis for the elimination of bacterial virulence in the case of plasmid mediated pathogenicity and antibiotic resistance. The large number of compounds tested for antiplasmid effects provides opportunities for QSAR studies in order to find a correlation between the antiplasmid effect and the supramolecular chemistry of these plasmid curing compounds. Plasmid elimination in vitro provides a method of isolating plasmid free bacteria for biotechnology without any risk of inducing mutations.

Effect of Essential Oils on Pathogenic Bacteria

Abstract: The increasing resistance of microorganisms to conventional chemicals and drugs is a serious and evident worldwide problem that has prompted research into the identification of new biocides with broad activity. Plants and their derivatives, such as essential oils, are often used in folk medicine. In nature, essential oils play an important role in the protection of plants. Essential oils contain a wide variety of secondary metabolites that are capable of inhibiting or slowing the growth of bacteria, yeasts and moulds. Essential oils and their components have activity against a variety of targets, particularly the membrane and cytoplasm, and in some cases, they completely change the morphology of the cells. This brief review describes the activity of essential oils against pathogenic bacteria.

Essential oils in combination and their antimicrobial properties.

Abstract: Essential oils (EOs) have been long recognized for their antibacterial, antifungal, antiviral, insecticidal and antioxidant properties. They are widely used in medicine and the food industry for these purposes. The increased interest in alternative natural substances is driving the research community to find new uses and applications of these substances. EOs and their components show promising activities against many food-borne pathogens and spoilage microorganisms when tested in vitro. In food systems, higher concentrations of EOs are needed to exert similar antibacterial effects as those obtained in in vitro assays. The use of combinations of EOs and their isolated components are thus new approaches to increase the efficacy of EOs in foods, taking advantage of their synergistic and additive effects. The purpose of this review is to provide an overview on the antimicrobial efficacy of these combinations. A survey of the methods used for the determination of the interactions and mechanisms involved in the antimicrobial activities of these combinations are also reported.

Efflux-mediated drug resistance in bacteria: an update.

Abstract: Drug efflux pumps play a key role in drug resistance and also serve other functions in bacteria. There has been a growing list of multidrug and drug-specific efflux pumps characterized from bacteria of human, animal, plant and environmental origins. These pumps are mostly encoded on the chromosome, although they can also be plasmid-encoded. A previous article in this journal provided a comprehensive review regarding efflux-mediated drug resistance in bacteria. In the past 5 years, significant progress has been achieved in further understanding of drug resistance-related efflux transporters and this review focuses on the latest studies in this field since 2003. This has been demonstrated in multiple aspects that include but are not limited to: further molecular and biochemical characterization of the known drug efflux pumps and identification of novel drug efflux pumps; structural elucidation of the transport mechanisms of drug transporters; regulatory mechanisms of drug efflux pumps; determining the role of the drug efflux pumps in other functions such as stress responses, virulence and cell communication; and development of efflux pump inhibitors. Overall, the multifaceted implications of drug efflux transporters warrant novel strategies to combat multidrug resistance in bacteria.