Dr. Laura Marise de Freitas Profile

Dr. Laura Marise de Freitas

Doctoral Candidate at UNESP

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Publications (2)

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Proceedings Article | 7 August 2019 Paper

Antimicrobial PDT in South America

Laura de Freitas, Maurício Baptista

Proceedings Volume 11070, 110708L (2019) https://doi.org/10.1117/12.2527507

KEYWORDS: Bacteria, Photodynamic therapy, Databases, Resistance

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Researchers all over the world have turned their attention to find novel antibiotics and non-antibiotic-based alternatives to fight infections caused by resistant bacteria. Among the alternatives, antimicrobial photodynamic therapy (aPDT) has gained attention due to its non-specific nature of killing, which is unlikely to induce new forms of resistance due mainly to its broad spectrum of action. Most research groups working in aPDT are based in the North and South Americas, and Brazil leads this research field, accounting for 26% of all the aPDT publications in the world, 55% of the Americas and more than 95% of the publications in South America alone. As far as the databases show, aPDT is the only research topic in which Brazil publishes more papers than any other country in the world. Brazilian researchers have been contributing extensively to unveil molecular mechanisms of aPDT, developing treatment protocols for oral, dermatologic and veterinary infections, and to improve and optimize the technique so it can finally become a clinical reality. However, if one analyses the average citation per paper, one will find that Brazilian papers, although abundant, receive fewer citations than almost all other countries in the top 10. This finding is not specific to this area of research since other scientometric studies have shown the same profile in many other research areas. The low global impact of Brazilian – and South America’s - research might be due to the immaturity of our community and/or unfamiliarity or lack of access to techniques that can help improve the robustness of the work. Therefore, collaborations among aPDT groups can be of the utmost importance in increasing the impact of science in South America. In this paper, we cover the numbers of South America’s research and provide a full network list to encourage scientific collaborations.

Proceedings Article | 14 March 2018 Presentation

Antimicrobial photodynamic therapy proved not to induce bacterial resistance (Conference Presentation)

Laura de Freitas, Ana Blanco, Carla Fontana

Proceedings Volume 10479, 1047919 (2018) https://doi.org/10.1117/12.2287268

KEYWORDS: Resistance, Photodynamic therapy, Picosecond phenomena, Oxygen, Therapeutics, Plating, Blood

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The World Health Organization has been alerting that the “post-antibiotic era” is approaching, making the search for alternative antimicrobial therapies mandatory. Antimicrobial photodynamic therapy (aPDT) has been gaining prominence due to its non-specific mechanism of action, which relies on the generation of reactive oxygen species upon the activation of a photosensitizer (PS) by light of a specific wavelength in the presence of oxygen. However, the discussion of whether or not aPDT can induce bacterial resistance is controversial. In that sense, the aim of this study was to determine if multiple cycles of suboptimal doses of aPDT could induce resistance in Enterococcus faecalis. First, we determined optimal and suboptimal conditions of aPDT employing chlorin-e6 (Ce6) and methylene (MB) for planktonic E. faecalis. The combinations of light dose and PS concentration that induced bacterial reductions between 1 log10 and 3 log10 of CFU/mL were selected to start the cycles (21 µM of Ce6 + 45 J/cm²; and 78 µM of MB + 80 J/cm²). The cycling consisted of treatment, plating on PS-free blood agar and recovering grown colonies to start again. By the end of four cycles, cells treated with both Ce6-aPDT or MB-aPDT were completely eliminated, after sustaining a stable survival rate through the first three cycles. We employed two different PS and observed the same outcomes for both of them, indicating the results were not PS-dependent. Our findings are of paramount importance since they are in the way to prove that bacterial resistance cannot be induced by this approach.

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