Breaking down antibiotic resistance in methicillin-resistant Staphylococcus aureus: Combining antimicrobial photodynamic and antibiotic treatments.

The widespread use of antibiotics drives the evolution of antimicrobial-resistant bacteria (ARB), threatening patients and healthcare professionals. Therefore, the development of novel strategies to combat resistance is recognized as a global healthcare priority. The two methods to combat ARB are development of new antibiotics or reduction in existing resistances. Development of novel antibiotics is a laborious and slow-progressing task that is no longer a safe reserve against looming risks. In this research, we suggest a method for reducing resistance to extend the efficacious lifetime of current antibiotics. Antimicrobial photodynamic therapy (aPDT) is used to generate reactive oxygen species (ROS) via the photoactivation of a photosensitizer. ROS then nonspecifically damage cellular components, leading to general impairment and cell death. Here, we test the hypothesis that concurrent treatment of bacteria with antibiotics and aPDT achieves an additive effect in the elimination of ARB. Performing aPDT with the photosensitizer methylene blue in combination with antibiotics chloramphenicol and tetracycline results in significant reductions in resistance for two methicillin-resistant Staphylococcus aureus (MRSA) strains, USA300 and RN4220. Additional resistant S. aureus strain and antibiotic combinations reveal similar results. Taken together, these results suggest that concurrent aPDT consistently decreases S. aureus resistance by improving susceptibility to antibiotic treatment. In turn, this development exhibits an alternative to overcome some of the growing MRSA challenge.

High-Dose Photodynamic Therapy Increases Tau Protein Signals in Drosophila.

Amyloid-Detection and imaging of amyloid-ß plaques (Aß) has been a focus in the field of neurodegeneration (ND) due to the high correlation with Parkinson's and Alzheimer's diseases. Here, a novel approach is being proposed and developed to induce and assess those diseases. Photodynamic therapy (PDT) is applied to the fruit fly Drosophila melanogaster as a model of systemic oxidative stress to induce rapid Aß accumulation. Excised brains are evaluated by Brillouin-Raman spectroscopy and microscopy with UV surface emissions (MUSE) to interrogate physical property changes due to fixation and high-dose PDT. MUSE reveals reasonable autofluorescence in the spectral range of Aß, particularly for females, with increased signal once stained. A presence of significant mechanical changes in fresh brains treated with PDT compared to healthy controls is revealed using Brillouin spectroscopy. Aß plaque presence was confirmed with confocal analysis, with female PDT flies yielding nearly four-fold the mean intensity of controls, thus marking PDT as a potential neurodegenerative disease model. MUSE may serve as a viable early screening method for Aß presence and quantification in a research setting. This reduces the time for sample preparation and drastically decreases the cost of Aß quantification.

Toward peripheral nerve mechanical characterization using Brillouin imaging spectroscopy.

Significance: Peripheral nerves are viscoelastic tissues with unique elastic characteristics. Imaging of peripheral nerve elasticity is important in medicine, particularly in the context of nerve injury and repair. Elasticity imaging techniques provide information about the mechanical properties of peripheral nerves, which can be useful in identifying areas of nerve damage or compression, as well as assessing the success of nerve repair procedures. Aim: We aim to assess the feasibility of Brillouin microspectroscopy for peripheral nerve imaging of elasticity, with the ultimate goal of developing a new diagnostic tool for peripheral nerve injury in vivo. Approach: Viscoelastic properties of the peripheral nerve were evaluated with Brillouin imaging spectroscopy. Results: An external stress exerted on the fixed nerve resulted in a Brillouin shift. Quantification of the shift enabled correlation of the Brillouin parameters with nerve elastic properties. Conclusions: Brillouin microscopy provides sufficient sensitivity to assess viscoelastic properties of peripheral nerves.

Porcine vocal fold elasticity evaluation using Brillouin spectroscopy.

Significance: The vocal folds are critically important structures within the larynx which serve the essential functions of supporting the airway, preventing aspiration, and phonation. The vocal fold mucosa has a unique multilayered architecture whose layers have discrete viscoelastic properties facilitating sound production. Perturbations in these properties lead to voice loss. Currently, vocal fold pliability is inferred clinically using laryngeal videostroboscopy and no tools are available for in vivo objective assessment. Aim: The main objective of the present study is to evaluate viability of Brillouin microspectroscopy for differentiating vocal folds' mechanical properties against surrounding tissues. Approach: We used Brillouin microspectroscopy as an emerging optical imaging modality capable of providing information about local viscoelastic properties of tissues in noninvasive and remote manner. Results: Brillouin measurements of the porcine larynx vocal folds were performed. Elasticity-driven Brillouin spectral shifts were recorded and analyzed. Elastic properties, as assessed by Brillouin spectroscopy, strongly correlate with those acquired using classical elasticity measurements. Conclusions: These results demonstrate the feasibility of Brillouin spectroscopy for vocal fold imaging. With more extensive research, this technique may provide noninvasive objective assessment of vocal fold mucosal pliability toward objective diagnoses and more targeted treatments.

Photodynamic viral inactivation: Recent advances and potential applications.

Antibiotic-resistant bacteria, which are growing at a frightening rate worldwide, has put the world on a long-standing alert. The COVID-19 health crisis reinforced the pressing need to address a fast-developing pandemic. To mitigate these health emergencies and prevent economic collapse, cheap, practical, and easily applicable infection control techniques are essential worldwide. Application of light in the form of photodynamic action on microorganisms and viruses has been growing and is now successfully applied in several areas. The efficacy of this approach has been demonstrated in the fight against viruses, prompting additional efforts to advance the technique, including safety use protocols. In particular, its application to suppress respiratory tract infections and to provide decontamination of fluids, such as blood plasma and others, can become an inexpensive alternative strategy in the fight against viral and bacterial infections. Diverse early treatment methods based on photodynamic action enable an accelerated response to emerging threats prior to the availability of preventative drugs. In this review, we evaluate a vast number of photodynamic demonstrations and first-principle proofs carried out on viral control, revealing its potential and encouraging its rapid development toward safe clinical practice. This review highlights the main research trends and, as a futuristic exercise, anticipates potential situations where photodynamic treatment can provide a readily available solution.

Safety and delivery efficiency of a photodynamic treatment of the lungs using indocyanine green and extracorporeal near infrared illumination.

Photodynamic inactivation (PDI) is a promising alternative for combating infections caused by antimicrobial resistant bacteria. Pneumonias are among the most worrisome infections because of their high-mortality rate. Previous studies have demonstrated the feasibility of using PDI with extracorporeal light to treat pneumonia. In this study, we analyzed key parameters for the viability of this treatment, including the selectivity of the photodynamic response for pathogens over host cells. Our results showed that PDI can induce killing of Staphylococcus aureus (of up to 4.18 log for the strain Xen29 and 3.62 log for Xen36) under conditions where little or no toxicity for host cells is observed. We validated pulmonary delivery of the photosensitizer and light in mice, using photobleaching as an indicator, and demonstrated preservation of healthy tissues as evidence of the safety of the protocol. Overall, PDI displays low toxicity on host tissues, making it a promising tool for treatment of pneumonias caused by S. aureus and other important pathogens.