Browsing by Author "Pina, Cristina"
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- Antimicrobial effect of chitosan against periodontal pathogens biofilmsPublication . Costa, Eduardo M.; Silva, Sara; Pina, Cristina; Tavaria, Freni K.; Pintado, ManuelaOver the years authors have established that chitosan possesses significant antimicrobial activity against planktonic bacteria however, little is known about the effect of chitosan upon sessile microbial communities. The aim of this work was to assess the effect of chitosan against 5 periodontal pathogens, Porphyromonasgingivalis, Prevotellaintermedia, Prevotellabuccae, Tanerellaforsythensis and Aggregatibacter actinomycetemcomitans biofilm formation. The results obtained show that both high molecular weight and low molecular weight chitosan were capable of inhibiting biofilm formation and biofilm associated phenomena. Sub-MIC concentrations of chitosan inhibited single species biofilm formation up to 90% and dual species biofilms formation up to 80%. Furthermore analysis of the effect of chitosan upon quorum sensing showed inhibition values that reached 70% after 24h exposure to chitosan. The results obtained open new possibilities in the fight against biofilm formation in the oral cavity and the prevention of undesirable microbiological colonization following dental treatments.
- Degree of contamination of gutta-percha points by Staphylococcus aureus (MRSA/MSSA) strainsPublication . Teles, Ana Moura; Pina, Cristina; Cardoso, Inês Lopes; Tramontana, Antea; Cardoso, Miguel; Duarte, Ana Sofia; Bartolomeu, Maria; Noites, RitaMethicillin-resistant Staphylococcus aureus (MRSA) is considered one of the most harmful bacteria to human health. Dentistry, like all healthcare disciplines, places great emphasis on preventing scenarios that may result in cross-infection. Although various tested and already used materials are suitable for filling the root canal system, Gutta-Percha (GP) remains the preferred and widely accepted gold standard. Objective: We performed an in vitro analysis of the contamination of GP points, regarding the strains of Methicillin-resistant (MRSA) and Methicillin-sensitive (MSSA) Staphylococcus aureus, using classical microbiology methods and molecular biology techniques. Methods: Gutta-Percha points of two different brands from opened packages (already in use for 1 month) were collected for analysis. The assessment involved incubating the GP points in Brain Heart Infusion (BHI) medium to detect microbial growth. Growing microorganisms were plated on a selective and differential chromogenic medium for MRSA/MSSA strains, and the identification of isolates was confirmed by Polymerase Chain Reaction (PCR). In the case of microbial growth, the GP point was submitted to a disinfection protocol. Results: From the 315 collected GP points, only 6 (1.9%) resulted in being positive for microbial growth. After confirmation by PCR, only one sample of the six GP points was contaminated by MRSA, and the remaining five were MSSA-contaminated. The disinfection protocol was effective in all contaminated GP points. Conclusions: The Gutta-Percha points from opened pre-sterilized packages showed a very low degree of contamination by MRSA/MSSA. However, the detection of MSSA and MRSA strains raises concerns about potential contamination in dental clinic environments, and this risk cannot be considered negligible.
- Enhancement of apparent resistance to ethanol in Lactobacillus hilgardiiPublication . Couto, José António; Pina, Cristina; Hogg, TimThe survival of Lactobacillus hilgardii, a highly ethanol-tolerant organism, after an ethanol challenge at 25% (v/v) for 10 min, increased by several log cycles when cells, grown in the absence of ethanol, were pre-treated with 10% (v/v) ethanol, 15% (v/v) methanol or 2% (v/v) butanol for 4 h. A temperature upshift (25 to 40°C) before ethanol challenge demonstrated a similar enhancement of apparent resistance to ethanol. Ethanol shock enhanced apparent resistance to methanol, butanol and heat challenges. The addition of chloramphenicol to cells prior to any pre-treatment did not significantly diminish the increase in ethanol tolerance, suggesting that de novo protein synthesis is not required for induced tolerance in this organism