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- Lytic bacteriophages against multidrug-resistant Staphylococcus aureus, Enterococcus faecalis and Escherichia coli isolates from orthopaedic implant-associated infectionsPublication . Barros, Joana; Melo, Luís D.R.; Poeta, Patrícia; Igrejas, Gilberto; Ferraz, Maria Pia; Azeredo, Joana; Monteiro, Fernando J.Orthopaedic implant-associated infections are a devastating complication of orthopaedic surgery with a significant impact on patients and healthcare systems. The aims of this work were to describe the patterns of antimicrobial resistance, pathogenicity and virulence of clinical bacterial isolates from orthopaedic implant-associated infections and to further isolate and characterise bacteriophages that are efficient in controlling these bacteria. Staphylococcus aureus, Enterococcus faecalis and Escherichia coli isolated from orthopaedic infections showed multiresistance patterns to the most frequently used antibiotics in clinical settings. The presence of mobile genetic elements (mecA, Tn916/Tn1545 and intl1) and virulence determinants (icaB, cna, hlb, cylLs, cylM, agg, gelE, fsr and fimA) highlighted the pathogenicity of these isolates. Moreover, the isolates belonged to clonal complexes associated with the acquisition of pathogenicity islands and antimicrobial resistance genes by recombination and horizontal gene transfer. Bacteriophages vB_SauM_LM12, vB_EfaS_LM99 and vB_EcoM_JB75 were characterised and their ability to infect clinical isolates of S. aureus, E. faecalis and E. coli, respectively, was assessed. Morphological and genomic analyses revealed that vB_EfaS_LM99 and vB_EcoM_JB75 belong to the Siphoviridae and Myoviridae families, respectively, and no genes associated with lysogeny were found. The bacteriophages showed low latent periods, high burst sizes, broad host ranges and tolerance to several environmental conditions. Moreover, they showed high efficiency and specificity to infect and reduce clinical bacteria, including methicillin-resistant S. aureus and vancomycin-resistant enterococci. Therefore, the results obtained suggest that the bacteriophages used in this work are a promising approach to control these pathogens involved in orthopaedic implant-associated infections.
- Cerium and gentamicin antibacterial activity on loaded calcium-phosphates microspheresPublication . Ferraz, Maria Pia; Caetana, Vanessa; Soares, Stephanie; Coelho, Maria João; Cardoso, Inês Lopes; Magalhães, Ricardo; Pina, Cristina Maria San Román Gomes de; M A Lopes
- Alginate-nanohydroxyapatite hydrogel system: Optimizing the formulation for enhanced bone regenerationPublication . Barros, J.; Ferraz, Maria Pia; Azeredo, J.; Fernandes, M.H.; Gomes, P.S.; Monteiro, F.J.Ceramic/polymer-based biocomposites have emerged as potential biomaterials tofill, replace, repair or re-generate injured or diseased bone, due to their outstanding features in terms of biocompatibility, bioactivity,injectability, and biodegradability. However, these properties can be dependent on the amount of ceramiccomponent present in the polymer-based composite. Therefore, in the present study, the influence of nanohy-droxyapatite content (30 to 70 wt%) on alginate-based hydrogels was studied in order to evaluate the bestformulation for maximizing bone tissue regeneration. The composite system was characterized in terms ofphysic-chemical properties and biological response, within vitrocytocompatibility assessment with human os-teoblastic cells andex vivofunctional evaluation in embryonic chick segmental bone defects. The main mor-phological characteristics of the alginate network were not affected by the addition of nanohydroxyapatite.However, physic-chemical features, like water-swelling rate, stability at extreme pH values, apatite formation,and Ca2+release were nanoHA dose-dependent. Withinin vitrocytocompatibility assays it was observed thathydrogels with nanoHA 30% content enhanced osteoblastic cells proliferation and expression of osteogenictranscription factors, while those with higher concentrations (50 and 70%) decreased the osteogenic cell re-sponse.Ex vivodata underlined thein vitrofindings, revealing an enhanced collagenous deposition, trabecularbone formation and matrix mineralization with Alg-nanoHA30 composition, while compositions with highernanoHA content induced a diminished bone tissue response.The outcomes of this study indicate that nanohydroxyapatite concentration plays a major role in physic-chemical properties and biological response of the composite system and the optimization of the componentsratio must be met to maximize bone tissue regeneration.
- Inhibitory effect of 5-aminoimidazole-4-carbohydrazonamides derivatives against Candida spp. biofilm on nanohydroxyapatite substratePublication . Gabriel, C.; Grenho, L.; Cerqueira, Fátima; Medeiros, R.; Dias, A. M.; Ribeiro, A. I.; Proença, M. F.; Fernandes, M. H.; Sousa, J. C.; Monteiro, F. J.; Ferraz, M. P.Candida can adhere and form biofilm on biomaterials commonly used in medical devices which is a key attribute that enhances its ability to cause infections in humans. Furthermore, biomaterial-related infections represent a major therapeutic challenge since Candida biofilms are implicated in antifungal therapies failure. The goals of the present work were to investigate the effect of three 5-aminoimidazole-4-carbohydrazonamides, namely (Z)-5-amino-1-methyl-N'-aryl-1H-imidazole-4-carbohydrazonamides [aryl = phenyl (1a), 4-fluorophenyl (1b), 3-fluorophenyl (1c)], on Candida albicans and Candida krusei biofilm on nanohydroxyapatite substrate, a well-known bioactive ceramic material. To address these goals, both quantitative methods (by cultivable cell numbers) and qualitative evaluation (by scanning electron microscopy) were used. Compounds cytocompatibility towards osteoblast-like cells was also evaluated after 24 h of exposure, through resazurin assay. The three tested compounds displayed a strong inhibitory effect on biofilm development of both Candida species as potent in vitro activity against C. albicans sessile cells. Regarding cytocompatibility, a concentration-dependent effect was observed. Together, these findings indicated that the potent activity of imidazole derivatives on Candida spp. biofilms on nanohydroxyapatite substrate, in particular compound 1c, is worth further investigating.