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Research Project
Health Sciences Research Centre
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Publications
Evaluation of Bile Salts on the Survival and Modulation of Virulence of Aliarcobacter butzleri
Publication . Mateus, Cristiana; Maia, Cláudio J.; Domingues, Fernanda; Bücker, Roland; Oleastro, Mónica; Ferreira, Susana
Aliarcobacter butzleri is a Gram-negative bacterium associated with infections of the gastrointestinal tract and widely distributed in various environments. For successful infection, A. butzleri should be able to tolerate various stresses during gastrointestinal passage, such as bile. Bile represents an antimicrobial host barrier that acts against external noxious agents and consists of a variety of bile salts. The intestinal bile salts act as detergents involved in the antimicrobial host defense; although, on the bacterial side, they could also serve as a signal to activate virulence mechanisms. The aim of this work was to understand the effects of bile salts on the survival and virulence of A. butzleri. In our study, A. butzleri was able to survive in the presence of human physiological concentrations of bile salts. Regarding the virulence features, an increase in cellular hydrophobicity, a decrease in motility and expression of flaA gene, as well as an increase in biofilm formation with a concomitant change in the type of biofilm structure were observed in the presence of sub-inhibitory concentration of bile salts. Concerning adhesion and invasion ability, no significant difference was observed. Overall, the results demonstrated that A. butzleri is able to survive in physiological concentrations of bile salts and that exposure to bile salts could change its virulence mechanisms.
Effect of Atmospheric Conditions on Pathogenic Phenotypes of Arcobacter butzleri
Publication . Martins, Rodrigo; Mateus, Cristiana; Domingues, Fernanda; Bücker, Roland; Oleastro, Mónica; Ferreira, Susana
Arcobacter butzleri is an emergent gram-negative enteropathogenic bacterium widespread in different environments and hosts. During the colonization of the gastrointestinal tract, bacteria face a variety of environmental conditions to successfully establish infection in a new host. One of these challenges is the fluctuation of oxygen concentrations encountered not only throughout the host gastrointestinal tract and defences but also in the food industry. Oxygen fluctuations can lead to modulations in the virulence of the bacterium and possibly increase its pathogenic potential. In this sense, eight human isolates of A. butzleri were studied to evaluate the effects of microaerobic and aerobic atmospheric conditions in stressful host conditions, such as oxidative stress, acid survival, and human serum survival. In addition, the effects on the modulation of virulence traits, such as haemolytic activity, bacterial motility, biofilm formation ability, and adhesion and invasion of the Caco-2 cell line, were also investigated. Overall, aerobic conditions negatively affected the susceptibility to oxygen reactive species and biofilm formation ability but improved the isolates’ haemolytic ability and motility while other traits showed an isolate-dependent response. In summary, this work demonstrates for the first time that oxygen levels can modulate the potential pathogenicity of A. butzleri, although the response to stressful conditions was very heterogeneous among different strains.
Putative Role of an ABC Efflux System in Aliarcobacter butzleri Resistance and Virulence
Publication . Martins, Inês; Mateus, Cristiana; Domingues, Fernanda; Oleastro, Mónica; Ferreira, Susana
Abstract: Aliarcobacter butzleri is considered a ubiquitous microorganism and emergent pathogen,
for which increasing rates of multidrug resistance have been described. In line with this, the present
work aimed to evaluate for the first time the contribution of an ABC efflux system, the YbhFSR, in
the resistance and virulence of this bacterium. Following the in silico characterization of the YbhFSR
transporter, a mutant strain was constructed by inactivating the gene responsible for ATP-binding.
After ensuring that the mutation did not have an impact on bacterial growth, the resistance profile
of parental and mutant strains to different antimicrobial agents was evaluated. The results suggest
that the efflux pump may influence the resistance to benzalkonium chloride, ethidium bromide,
and cadmium, and several other compounds were identified as potential substrates. Regarding
the evaluation of the accumulation of ethidium bromide, a slight increase was observed for the
mutant strain, demonstrating a potential role of the YbhFSR efflux pump in the extrusion of toxic
compounds from A. butzleri. Subsequently, the role of this efflux pump on the A. butzleri known
virulence properties was evaluated, but no difference was seen among mutant and parental strains
for the motility, biofilm formation ability, susceptibility to oxidative stress, or the ability to adhere and
invade Caco-2 cells. However, in contrast to the parental strain, the mutant strain showed a resistance
to human serum. Overall, the results support the role of efflux pumps in A. butzleri resistance to
antimicrobials, highlighting the particular role of the YbhFSR system.
The Prevalence of Arcobacteraceae in Aquatic Environments: A Systematic Review and Meta-Analysis
Publication . Venâncio, Igor; Luís, Ângelo; Domingues, Fernanda; Oleastro, Mónica; Pereira, Luísa; Ferreira, Susana
Members of the family Arcobacteraceae are distributed widely in aquatic environments, and some of its species have been associated with human and animal illness. However, information about the diversity and distribution of Arcobacteraceae in different water bodies is still limited. In order to better characterize the health risk posed by members in the family Arcobacteraceae, a systematic review and meta-analysis-based method was used to investigate the prevalence of Arcobacteraceae species in aquatic environments based on available data published worldwide. The database search was performed using related keywords and considering studies up to February 2021. The pooled prevalence in aquatic environments was 69.2%, ranging from 0.6 to 99.9%. These bacteria have a wide geographical distribution, being found in diverse aquatic environments with the highest prevalence found in raw sewage and wastewater treatment plants (WWTP), followed by seawater, surface water, ground water, processing water from food processing plants and water for human consumption. Assessing the effectiveness of treatments in WWTP in eliminating this contamination, it was found that the wastewater treatment may not be efficient in the removal of Arcobacteraceae. Among the analyzed Arcobacteraceae species, Al. butzleri was the most frequently found species. These results highlight the high prevalence and distribution of Arcobacteraceae in different aquatic environments, suggesting a risk to human health. Further, it exposes the importance of identifying and managing the sources of contamination and taking preventive actions to reduce the burden of members of the Arcobacteraceae family.
Chemical characterization and bioactive potential of Thymus × citriodorus (Pers.) Schreb. preparations for anti-acne applications: Antimicrobial, anti-biofilm, anti-inflammatory and safety profiles
Publication . Oliveira, Ana S.; Rolo, Joana; Gaspar, Carlos; Cavaleiro, Carlos; Salgueiro, Lígia; Palmeira-de-Oliveira, Rita; Ferraz, Celso; Coelho, Susana; Pastorinho, M. Ramiro; Sousa, Ana Catarina; Teixeira, João Paulo; Martinez-de-Oliveira, José; Palmeira-de-Oliveira, Ana
Ethnopharmacological relevance: Thymus × citriodorus (Pers.) Schreb. is an interspecific hybrid between Thymus pulegioides and Thymus vulgaris, known for its pharmacological activities as diaphoretic, deodorant, antiseptic and disinfectant, the last mostly related with its antimicrobial activity. The folk use of other extracts, as hydrolates, have also been disseminated, as regulators of oily skin with anti-acne effect.
Aim of the study: We aimed to evaluate the anti-acne potential of two Thymus x citriodorus (TC) preparations, the essential oil (EO) and the hydrolate, to be used as active ingredients for skin applications. Specifically, we intend to validate their anti-acne potential by describing their activity on acne related bacteria, bacterial virulence, anti-oxidant and anti-inflammatory potential, and biocompatibility on inflammatory cells. Additionally, we aimed to report their ecotoxicity under the Globally Harmonized System of Classification and Labelling of Chemicals (GHS), thus focusing not only on the consumer, but also on environmental safety assessment.
Materials and methods: Minimum inhibitory concentration (MIC) against C. acnes, S. aureus and S. epidermidis was evaluated. Minimum lethal concentration (MLC) was also determined. The effect on C. acnes biofilm formation and disruption was evaluated with crystal violet staining. Anti-inflammatory activity was investigated on LPS-stimulated mouse macrophages (RAW 264.7), by studying nitric oxide (NO) production (Griess reagent) and cellular biocompatibility through MTT assay. In-vitro NO and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging potential were also evaluated. The ecotoxicity was evaluated using Daphnia magna acute toxicity assays.
Results: EO presented direct antimicrobial activity, with visual MICs ranging from 0.06% for S. epidermidis and C. acnes to 0.125% for S. aureus. MLCs were higher than the obtained MICs. Hydrolate revealed visual MIC only for C. acnes. TC essential oil was effective in preventing biofilm formation and disrupting preformed biofilms even at sub-inhibitory concentrations. Hydrolate showed a more modest anti-biofilm effect. Regarding anti-inflammatory activity, TC hydrolate has a higher cellular biocompatibility. Still, both plant preparations were able to inhibit at least 50% of NO production at non-cytotoxic concentrations. Both EO and hydrolate have poor anti-oxidant activities. Regarding the ecotoxicity, TC essential oil was classified under acute 3 category, while the hydrolate has proved to be nontoxic, in accordance to the GHS.
Conclusions: These results support the anti-acne value of different TC preparations for different applications. TC hydrolate by presenting higher biocompatibility, anti-inflammatory potential and the ability to modulate C. acnes virulence, can be advantageous in a product for everyday application. On the other hand, EO by presenting a marked antimicrobial, anti-biofilm and anti-inflammatory activities, still with some cytotoxicity, may be better suited for application in acute flare-ups, for short treatment periods.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
6817 - DCRRNI ID
Funding Award Number
UIDB/00709/2020