Percorrer por autor "Oliveira, Manuela"
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- Bacteriostatic and antibiofilm efficacy of a Nisin Z solution against co-cultures of Staphylococcus aureus and Pseudomonas aeruginosa from diabetic foot infectionsPublication . Serrano, Isa; Alhinho, Bernardo; Cunha, Eva; Tavares, Luís; Trindade, Alexandre; Oliveira, ManuelaDiabetes mellitus (DM) patients frequently develop diabetic foot ulcers (DFU) which are generally infected by a community of microorganisms, mainly Staphylococcus aureus and Pseudomonas aeruginosa. These bacteria exhibit a multi-drug resistance profile and biofilm-forming ability which represent a hurdle in the treatment of diabetic foot infections (DFI). We aimed to evaluate the potential of Nisin Z, an antimicrobial peptide (AMP), as an alternative treatment for severe DFI. Nisin Z shows antibacterial activity against Gram-positive and Gram-negative bacteria and an increased antibacterial effect against Gram-negatives when added to EDTA. As such, Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Minimum Biofilm Inhibitory Concentration (MBIC), and Minimum Biofilm Eradication Concentration (MBEC) were determined for Nisin Z, Nisin Z + EDTA (0.4%), and Nisin Z + EDTA incorporated into guar gum, in order to test its efficacy against S. aureus and P. aeruginosa isolated from the same DFU. Results showed that Nisin Z added to the chelation agent EDTA displayed higher antibacterial and bacteriostatic efficacy against mono and dual co-cultures of S. aureus and P. aeruginosa, and higher antibiofilm efficiency against monocultures. Nisin Z was moderately cytotoxic at 200 µg/mL. Prospect in vivo studies are needed to confirm the potential of Nisin Z supplemented with EDTA to be used as a complement to conventional antibiotic therapy for severe DFI.
- Characterization of multidrug-resistant diabetic foot ulcer enterococciPublication . Semedo-Lemsaddek, Teresa; Mottola, Carla; Alves-Barroco, Cynthia; Cavaco-Silva, Patrícia; Tavares, Luís; Oliveira, ManuelaIntroduction: Diabetes mellitus is a highly prevalent chronic progressive disease with complications that include diabetic-foot ulcers. Methods: Enterococci isolated from diabetic-foot infections were identified, evaluated by macrorestriction analysis, and screened for virulence traits and antimicrobial resistance. Results: All isolates were considered multidrug-resistant, cytolysin and gelatinase producers, and the majority also demonstrated the ability to produce biofilms. Conclusions: These results indicate the importance of enterococci in diabetic-foot infection development and persistence, especially regarding their biofilm-forming ability and resistance to clinically relevant antibiotics.
- In vitro design of a novel lytic bacteriophage cocktail with therapeutic potential against organisms causing diabetic foot infectionsPublication . Mendes, João J.; Leandro, Clara; Mottola, Carla; Barbosa, Raquel; Silva, Filipa A.; Oliveira, Manuela; Vilela, Cristina L.; Melo-Cristino, José; Górski, Andrzej; Pimentel, Madalena; São-José, Carlos; Cavaco-Silva, Patrícia; Garcia, MiguelIn patients with diabetes mellitus, foot infections pose a significant risk. These are complex infections commonly caused by Staphylococcus aureus, Pseudomonas aeruginosa and Acinetobacter baumannii, all of which are potentially susceptible to bacteriophages. Here, we characterized five bacteriophages that we had determined previously to have antimicrobial and wound-healing potential in chronic S. aureus, P. aeruginosa and A. baumannii infections. Morphological and genetic features indicated that the bacteriophages were lytic members of the family Myoviridae or Podoviridae and did not harbour any known bacterial virulence genes. Combinations of the bacteriophages had broad host ranges for the different target bacterial species. The activity of the bacteriophages against planktonic cells revealed effective, early killing at 4 h, followed by bacterial regrowth to pre-treatment levels by 24 h. Using metabolic activity as a measure of cell viability within established biofilms, we found significant cell impairment following bacteriophage exposure. Repeated treatment every 4 h caused a further decrease in cell activity. The greatest effects on both planktonic and biofilm cells occurred at a bacteriophage : bacterium input multiplicity of 10. These studies on both planktonic cells and established biofilms allowed us to better evaluate the effects of a high input multiplicity and a multiple-dose treatment protocol, and the findings support further clinical development of bacteriophage therapy.