Utility of realistic microscopy-based cell models in simulation studies of nanoparticle-enhanced photon radiotherapy.

To enhance the effect of radiation on the tumor without increasing the dose to the patient, the combination of high-Z nanoparticles with radiotherapy has been proposed. In this work, we investigate the effects of the physical parameters of nanoparticles (NPs) on the Dose Enhancement Factor (DEF), and on the Sensitive Enhancement Ratio (SER) by applying a version of the Linear Quadratic Model. A method for constructing voxelized realistic cell geometries in Monte Carlo simulations from confocal microscopy images was developed and applied to Gliobastoma Multiforme cell lines (U87 and U373). The comparison of simulations with realistic geometry and spherical geometry shows that there is significant impact on the survival curves obtained for the same irradiation conditions. Using this model, the DEF and the SER are determined as a function of the concentration, size and distribution of gold nanoparticles within the cell. For small NPs,dAuNP= 10 nm, no clear trend in the DEF and SER was observed when the number of NPs within the cell increases. Experimentally, the variable number of NPs measured inside the U373 cells (ranging between 1.48 × 105and 1.19 × 106) also did not influence much the observed cell survival upon irradiation of the cells with a Co-60 source. The same lack of trend is obtained when the Au content in the cell is kept constant, 0.897 mg/g, but the size of the NPs is changed. However, if the number of NPs is kept constant (7.91 × 105) and the size changes, there is a critical diameter above which the dose effect increases significantly. Using the realistic geometries, it was verified that the key parameter for the DEF and the SER enhancement is the volume fraction of Au in the cell, with NP size being a more important parameter than the number of NPs.

Possible Trichosporon asahii urinary tract infection in a critically ill COVID-19 patient.

BACKGROUND: Trichosporon asahii, an emerging fungal pathogen, has been frequently associated with invasive infections in critically ill patients. CASE REPORT: A 74-year-old male patient diagnosed with COVID-19 was admitted to an Intensive Care Unit (ICU). During hospitalization, the patient displayed episodes of bacteremia by Staphylococcus haemolyticus and a possible urinary tract infection by T. asahii. While the bacterial infection was successfully treated using broad-spectrum antibiotics, the fungal infection in the urinary tract was unsuccessfully treated with anidulafungin and persisted until the patient died. CONCLUSIONS: With the evolving COVID-19 pandemic, invasive fungal infections have been increasingly reported, mainly after taking immunosuppressant drugs associated with long-term broad-spectrum antibiotic therapy. Although Candida and Aspergillus are still the most prevalent invasive fungi, T. asahii and other agents have emerged in critically ill patients. Therefore, a proper surveillance and diagnosing any fungal infection are paramount, particularly in COVID-19 immunocompromised populations.

Possible Trichosporon asahii urinary tract infection in a critically ill COVID-19 patient

Background:Trichosporon asahii, an emerging fungal pathogen, has been frequently associated with invasive infections in critically ill patients.Case report:A 74-year-old male patient diagnosed with COVID-19 was admitted to an Intensive Care Unit (ICU). During hospitalization, the patient displayed episodes of bacteremia by Staphylococcus haemolyticus and a possible urinary tract infection by T. asahii. While the bacterial infection was successfully treated using broad-spectrum antibiotics, the fungal infection in the urinary tract was unsuccessfully treated with anidulafungin and persisted until the patient died.Conclusions:With the evolving COVID-19 pandemic, invasive fungal infections have been increasingly reported, mainly after taking immunosuppressant drugs associated with long-term broad-spectrum antibiotic therapy. Although Candida and Aspergillus are still the most prevalent invasive fungi, T. asahii and other agents have emerged in critically ill patients. Therefore, a proper surveillance and diagnosing any fungal infection are paramount, particularly in COVID-19 immunocompromised populations. (AU)

Antecedentes:Trichosporon asahii, un hongo patógeno emergente, se ha asociado con frecuencia con infecciones invasivas en pacientes enfermos en estado crítico.Caso clínico:Un paciente de sexo masculino de 74 años de edad, con diagnóstico positivo para la COVID-19, ingresó en una unidad de cuidados intensivos. Durante la hospitalización el paciente presentó episodios de bacteriemia por Staphylococcus haemolyticus y una posible infección del tracto urinario por T. asahii. Mientras la infección bacteriana fue tratada exitosamente con antibióticos de amplio espectro, la infección micótica urinaria no remitió con anidulafungina y persistió hasta la muerte del paciente.Conclusiones:Con la pandemia de la COVID-19 se han notificado cada vez más casos de infecciones micóticas invasivas, principalmente después del uso de fármacos inmunosupresores, asociados con terapia de antibióticos de amplio espectro. Aunque Candida y Aspergillus siguen siendo los hongos invasores más prevalentes, T.asahii y otras especies han emergido en pacientes enfermos en estado crítico. Por lo tanto, la vigilancia y el diagnóstico de las infecciones micóticas es primordial, particularmente en poblaciones inmunodeficientes por la COVID-19. (AU)