Browsing by Author "Domingues, F.C."
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- Antioxidant properties of coriander essential oil and linalool and their potential to control Campylobacter spp.Publication . Duarte, A.; Luís, A.; Oleastro, Mónica; Domingues, F.C.Foodborne diseases remain common around the world with Campylobacteriosis being the most commonly reported zoonosis in the European Union in 2013. Campylobacter jejuni and Campylobacter coli are the main species associated with human illness. Furthermore, Campylobacter can develop biofilms which is becoming a major problem within the food industry. In addition to foodborne pathogens, oxidation is a non-microbial cause of deterioration of food causing loss of quality and safety. Thus, there is an urgent need in the food industry for new and effective strategies that can help prevent food contamination, spoilage and consequently, foodborne illnesses. Essential oils are known for their antimicrobial and antioxidant properties and are already widely used in the food industry. So, the aim of this work was to study the antimicrobial and anti-biofilm activity of coriander essential oil and its major compound linalool against C. jejuni and C. coli strains, as well as their effect in the quorum sensing (QS) system and their potential as antioxidants. Our results, demonstrated that both compounds have anti- Campylobacter activity, inhibited in vitro biofilm formation and promoted biofilm dispersion even at sub-MIC concentrations and interfered with the QS system through the inhibition of violacein production. Moreover, the essential oil and linalool were shown to have radical scavenging properties and lipid peroxidation inhibition ability which could make them potential alternatives to synthetic antioxidants. In sum, our results demonstrated the antibacterial, anti-biofilm, anti-QS and antioxidant potentials of the coriander essential oil and its major compound, linalool, suggesting that they could be used in the food industry to enhance shelf life of food products and increase food safety without requiring chemical additives or preservatives.
- Genotypic and phenotypic features of Arcobacter butzleri pathogenicityPublication . Ferreira, S.; Queiroz, J.A.; Oleastro, M.; Domingues, F.C.Even though Arcobacter butzleri has been implicated in some human disease as diarrhoea and bacteraemia, much of its pathogenesis and virulence factors remain unclear. In this work we have compared pathogenic and genotypic properties of six A. butzleri isolates from human and non-human sources. The tested isolates showed to be susceptible to tetracyclines and aminoglycosides, however non-human isolates were all resistant to quinolones. The ability to form biofilms was variable among the tested strains, and all of them showed a weak haemolytic activity. The presence of nine putative virulence genes was determined, with cadF, ciaB, cj1349, mviN, pldA, tlyA being detected in all strains, while irgA (3/6), hecA (5/6), hecB (4/6) were detected only in some strains. High levels of adhesion were observed for A. butzleri on Caco-2 cells, with pre-existing inflammation showing no significant effect on the adherence ability; yet variable levels of invasion were observed. A. butzleri isolates were able to survive intracellularly in Caco-2 cells and to induce a significant up-regulation of interleukin-8 secretion and structural cell rearrangements. These data brings new insights on A. butzleri virulence and highlights its pathogenic potential.
- Human, food and animal Campylobacter spp. isolated in Portugal: high genetic diversity and antibiotic resistance ratesPublication . Duarte, A.; Santos, A.; Manageiro, V.; Martins, A.; Fraqueza, M.J.; Caniça, Manuela; Domingues, F.C.; Oleastro, M.Infections by Campylobacter jejuni and Campylobacter coli are considered the major cause of bacterial gastroenteritis in humans, with food being the main source of infection. In this study, a total of 196 Campylobacter strains (125 isolates from humans, 39 from retail food and 32 from food animal sources) isolated in Portugal between 2009 and 2012 were characterised by multilocus sequence typing (MLST) and flaA short variable region (SVR) typing. Susceptibility to six antibiotics as well as the mechanisms underlying antibiotic resistance phenotypes was also studied. Based on MLST typing, C. coli strains were genetically more conserved, with a predominant clonal complex (CC828), than C. jejuni strains. In contrast, C. coli isolates were genetically more variable than C. jejuni with regard to flaA-SVR typing. A high rate of resistance was observed for quinolones (100% to nalidixic acid, >90% to ciprofloxacin) and, in general, resistance was more common among C. coli, especially for erythromycin (40.2% vs. 6.7%). In addition, most isolates (86%) were resistant to multiple antimicrobial families. Besides the expected point mutations associated with antibiotic resistance, detected polymorphisms in the cmeABC locus likely play a role in the multiresistant phenotype. This study provides for the first time an overview of the genetic diversity of Campylobacter strains from Portugal. It also shows a worrying antibiotic multiresistance rate and the emergence of Campylobacter strains resistant to antibiotics of human use.
- Insights in the pathogenesis and resistance of Arcobacter: A reviewPublication . Ferreira, S.; Queiroz, J.A.; Oleastro, Mónica; Domingues, F.C.Arcobacter genus currently comprises 18 recognized species, among which Arcobacter butzleri, Arcobacter cryaerophilus and Arcobacter skirrowii have been associated with human and animal disease. Although these organisms, with special emphasis A. butzleri, are emerging as clinical pathogens, several aspects of their epidemiology and virulence are only starting to be clarified. In vitro human and animal cell culture assays have been used to show that several Arcobacter species can adhere to and invade eukaryotic cells, induce an immune response and produce toxins that damage host cells. In addition, data from genome sequencing highlighted several potential markers that may be helpful candidates for the study and understanding of these mechanisms; however, more work is necessary to clarify the molecular mechanisms involved in Arcobacter virulence. Arcobacter can be considered a relatively robust organism showing to be able to survive in adverse conditions, as the ones imposed by food processing and storage. Moreover, these bacteria have shown increased antibiotic resistance, along with high multidrug resistance. In this review, we seek to update the state-of-the-art concerning Arcobacter distribution, its interaction with the host, the trends of antibiotic resistance, its ability to survive, and finally the use of natural antimicrobials for control of Arcobacter.
- Resveratrol against Arcobacter butzleri and Arcobacter cryaerophilus: activity and effect on cellular functionsPublication . Ferreira, S.; Silva, F.; Queiróz, J.A.; Oleastro, M.; Domingues, F.C.The frequent isolation of Arcobacter butzleri and Arcobacter cryaerophilus from food samples makes it imperative to search for potential compounds able to inhibit the development of these bacteria. Taking this into consideration, this study focuses on the antimicrobial activity of resveratrol and its mechanism of action against A. butzleri and A. cryaerophilus. The activity of resveratrol was assessed by a microdilution method and time– kill curves. Resveratrol effect on cellular functions was assessed by flow cytometry evaluating intracellular DNA content and metabolic activity. Ethidium bromide (EtBr) accumulation in the presence of resveratrol was also evaluated, as well as the susceptibility to resveratrol in the presence of phenylalanine-arginine β- naphthylamide (PAβN). Scanning electron microscopy (SEM) was used to further evaluate cell damage caused by resveratrol. Resveratrol presented MIC values of 100 and 50 μg/mL to A. butzleri and A. cryaerophilus, respectively. Based on the time–kill curves, resveratrol exhibited bactericidal activity, leading to a ≥3 log10 CFU/mL reduction of initial inoculums, for A. butzleri exponential phase cells incubated for 6 h with 1× MIC or with 2× MIC after 24 h for stationary phase cells. For A. cryaerophilus cells in exponential growth phase, 99.9% killing was achieved after 24 h incubation with 2× MIC,whereas, for stationary phase cells, bactericidal activitywas only detected after incubation with 4×MIC. Incubation with resveratrol led to a decrease in both intracellular DNA content and metabolic activity. An increase in the accumulation of EtBr was observed in the presence of resveratrol, and the efflux pump inhibitor PAβN reduced the MIC of resveratrol. SEM analysis revealed disintegration of A. butzleri cells treated with resveratrol, whereas no morphological alteration was observed for A. cryaerophilus cells. Resveratrol has a good anti-Arcobacter activity, and the results obtained suggest that this compound could act through several different mechanisms in the inhibition of this microorganism. The results encourage the use of this compound for the development of potential strategies to control Arcobacter in food products.