Challenges and perspectives in research and teaching of host pathogen interaction topics: new post-pandemic times to Brazil and other South American countries

Here is our proposal to improve learning in biomedical sciences for graduate and undergraduate courses with a broad vision integrating disciplines such as molecular cell biology, biochemistry, and biophysics around concepts of pathogen interaction within vertebrate and invertebrate hosts. Our paradigm is based on the possibility offered by the pandemic to have remote activities that give access to students and researchers from different places in Brazil and Latin American countries to discuss science. A multidisciplinary view of host-pathogen interaction allows us to understand better the mechanisms involved in the pathology of diseases, as well as to formulate broad strategies for the diagnosis, treatment, and control of thereof. The approach to integrating heterogeneous groups in science involves the critical analysis of national scientific resource distribution, where only some have the possibilities to conduct competitive scientific research. Solid theoretical training, contact, collaboration with groups of excellence, and training within a multidisciplinary network are our proposals for a permanent platform of scientific strengthening and dissemination for Latin America. Here we will review the concept of host-pathogen interaction, the type of institutions where it is taught and researched, new trends in active teaching methodologies, and the current political context in science.

Evaluation of biofilm formation on acrylic resin surfaces coated with silicon dioxide: an in situ study

Abstract Biofilm on acrylic resin dental prostheses may cause gingival inflammation. This study evaluated the influence of a silicon dioxide coating layer applied onto acrylic resin on the adhesion of microorganisms. Blocks (5 x 5 x 3 mm) of acrylic resin were evaluated for surface roughness and divided into two groups: control (CG) and coated with silicon dioxide (LG group). The specimens were evaluated by scanning electron microscopy (n = 1) and by contact angle analysis (n = 3). For the in situ study, 20 volunteers wore acrylic palatal devices containing three samples from each group (n = 60) for 2 days. The biofilm formed was quantified by metabolic activity and total biomass using the crystal violet assay. The results were subjected to Bartlett's normality test and Gamma model with random effect for the response variable (α = 5%). The mean contact angle of the coated group was significantly lower than that of the uncoated group (p < 0.05). The metabolic activity of microorganisms in the biofilm on the blocks treated with coating was significantly lower than that of control blocks (p = 0.02). Regarding the amount of extracellular matrix produced by the microorganisms, there was no difference between the CG and LG group (p = 0.05). The application of a silicon dioxide coating on acrylic resin reduced the activity of the polymicrobial biofilm formed in situ. This coating may be advantageous for patients with conventional complete dentures or implants made of acrylic resin and who have motor difficulties that prevent them from cleaning their prostheses properly.

Standardization of resazurin use in susceptibility testing of natural products against yeasts in planktonic cells and in biofilms formation

Natural products, such as the ethanolic propolis extract (PE), have been shown to be a safe and effective therapeutic alternative for the treatment of fungal skin and nail diseases. However, the presence of the resin and the physicochemical characteristics of the extract sometimes difficult the reading and determination of breakpoints of the in vitrotests, evidencing the need for alternatives that facilitate the reading. The present study aimed to standardize the use of resazurin in tests of susceptibility of PE with planktonic yeast cells and biofilm forms. The antifungal activity of PE was determined by minimum inhibitory concentration (MIC) and we observed that, for all Candida spp. tested, the most reproducible MIC results were obtained when resazurin was placed after 24 hours of incubation and remained more 24 hourswith yeasts plus PE. For encapsulated yeasts, there was no dye reduction and color transition. Resazurin was also used for the evaluation of minimal biofilm inhibitory concentration and minimal biofilm eradication concentration and it was metabolized and reproducedthe action of PE on Candida biofilms. In addition, microdilution checkerboard plates were made with the dye, which assisted reading the result of the interaction between PE and nystatin. We observed that the resin, the color and the turbidity of the PE slightly changed the color of the resazurin in high concentrations of the extract and did not impair the reading. Therefore, the resazurin standardization tests were proven to be efficient and grounds that it should be used as an auxiliary methodology for reading and interpretation of the susceptibility tests for non-encapsulated yeasts with natural products, which form turbidity or precipitation, such as propolis.

Fatores de virulência e susceptibilidade a antifúngicos de Cryptococcus Spp / Virulence factors and susceptibility to Cryptococcus Spp. antifungals

Criptococose é uma doença grave que afeta tanto imunocomprometidos quanto imunocompetentes, com isso analisar a virulência é fundamental para novas terapêuticas. Objetivo: Analisar a capacidade de virulência e susceptibilidade aos antifúngicos de Cryptococcus spp. isolados de líquor de pacientes de hospital do norte do Paraná. Métodos: A partir de dois isolados clínicos C. neoformans e C. gattii, realizou-se a confirmação da identificação. Para a virulência, avaliou-se o tamanho da cápsula, capacidade de sobrevivência após exposição a neutrófilos, produção de melanina e urease. No antifungigrama por difusão em disco utilizou-se: anfotericina B, cetoconazol, voriconazol, itraconazol e miconazol. Resultados: C. gattii destaca-se por maior desenvolvimento da cápsula além da melhor capacidade de sobreviver a fagocitose em relação ao C. neoformans. No antifungigrama, ambos os isolados se apresentam sensíveis às drogas estudadas. Conclusão: Esses achados contribuem para a compreensão das diferentes patogêneses entre C. gattii e C. neoformans.

Cryptococcosis is a serious disease that can affect both immunocompromised and immunocompetent individuals, thus the virulence analysis is fundamental for the development of new treatments. Objective: To analyze the virulence and susceptibility of Cryptococcus spp. isolated from cerebrospinal fluid of patients from a hospital in the north of Paraná. Methods: From two clinical isolates, C. neoformans and C. gattii were confirmed and identified. For virulence, capsule size, survival capacity after exposure to neutrophils, melanin production and urease were evaluated. In the disc-diffusion method, the following antifungals were used: amphotericin B, ketoconazole, voriconazole, itraconazole and miconazole Results: It was observed that C. gattii presents greater results for development of the capsule beside presenting the best ability to survive phagocytosis in relation to C. neoformans. In the disc-diffusion method, both isolates presented sensitivity to the studied drugs. Conclusion: These findings contribute to the understanding of the different pathogens between C. gattii and C. neoformans.

Effect of Silicon dioxide coating of acrylic resin surfaces on Candida albicans adhesion

Abstract Acrylic resin has been used in the manufacture of prostheses, however, in the oral cavity, this material starts to retain microorganisms capable of causing gingival inflammation due its porosities. The aim of this study was to evaluate the influence of the use of silicon dioxide as a coating layer applied onto acrylic resin, on the adhesion of Candida albicans (Ca). After the incubation period in Sabouraud Dextrose Broth, a total of 1 ml of the Ca suspension was added to plate wells, each well containing a specimen of acrylic resin. The adhesion ability of Ca on acrylic resin was determined by counting colonies. Three groups (n = 6) of acrylic resin were assessed: with polishing (RP); without polishing (RW); with polishing and coating layer of silicon dioxide (RPC). Ca deposited on the surface of the acrylic resin was also observed using Scanning Electron Microscopy (SEM). Statistical assessment by Kruskal-Wallis and Student-Newman-Keuls Method were done (α = 2%). There was significant difference among the groups. The RPC group showed the lowest growth, with an average of 5.59 Log CFU/cm 2 ; there was a statistically significant difference in relation to group RW, which presented a growth of 6.07 Log CFU/cm 2 and to group RP with 5.91 Log CFU/cm 2 (p < 000.1). SEM images demonstrated that in the RP and RPC group, the surface of the resin had greater regularity, and smaller number of microorganisms. The application of silicon dioxide coating on acrylic resin appears to be a promising alternative, and its use can help in reducing the adhesion of Ca in prostheses.

Occurrence of dermatophytoses in patients from the Sistema Único de Saúde

Abstract: Background: Dermatophytosis is a cutaneous disease caused by filamentous keratinophilic fungi belonging to the genera Trichophyton, Microsporum and Epidermophyton, which present a high prevalence in the general population, being among the most common mycoses affecting about 20% of the world's population. Objective: To carry out the epidemiological survey of cases of dermatophytosis in patients from the Sistema Único de Saúde in a regional Laboratory in the period of 5 years (2009 to 2013). Methods: A retrospective study (January 2009 to December 2013) was carried out with a qualitative and quantitative design, through the registry book of the laboratory, Mycology Sector, where cases of patients with suspected dermatomycosis were analyzed. Results: In a 5-year period, a total of 4467 cases were suspected of having a fungal infection. Of these, 68.74% (3071) cases were of dermatomycosis. In relation to cultures with fungal growth, 12.54% (385 cases) were dermatophyte fungi and 7.97% (245 cases) non-dermatophyte fungi were isolated. Among the species identified, there was a higher prevalence of T. rubrum complex (75%), T. mentagrophytes complex (11.68%) and M. canis (7.01%). Regarding the sites analyzed, nail involvement was the most frequent in 75% of the cases. Study Limitations: This work is representative in the studied region. Conclusions: Dermatomycosis samples are the most frequent among all samples of fungal infections from these patients, with the nail being the most affected area and the fungi T. rubrum complex and T. mentagrophytes complex the most frequent.

Nanopartículas de prata biossintetizadas por mikania glomerata sprengel inibem o crescimento de candida albicans e staphylococcus aureus / Biosynthesized silver nanoparticles by mikania glomerata sprengel inhibit the growth of candida albicans and staphylococcus aureus

Introdução: Nos últimos anos ocorreu o aumento de casos relacionados com a infecção por Candida spp. e Staphylococcus spp., bem como o aparecimento de cepas resistentes a antibióticos convencionais. A biossíntese de nanopartículas consiste na redução de um íon metálico por compostos de origem natural como metabólitos secundários de plantas e organismos, sendo a forma mais indicada por apresentar menor toxicidade quando comparada à síntese química. Desta forma, a síntese biológica constitui uma alternativa para a obtenção de novos agentes ativos para o tratamento de infecções microbianas. Objetivos: Sintetizar nanopartículas de prata a partir do extrato aquoso de Mikania glomerata Sprengel e avaliar possível atividade microbicida e citotóxica. Material e Métodos: Para a síntese das nanopartículas de prata (AgNPs) foi utilizado um extrato aquoso das folhas de M. glomerata e uma solução de nitrato de prata. As AgNPs sintetizadas foram avaliadas por espectrofotômetro UV-vis e espectrometria de absorção atômica com chama. Além disso, a atividade antimicrobiana foi avaliada contra cepas de Candida albicans e Staphylococcus aureus e atividade citotóxica contra linhagens celulares HeLa e Vero. Resultados: As AgNPs são mais eficientes no combate à linhagem de Candida albicans e Staphylococcus aureus quando comparadas ao extrato puro administrado. Até a concentração de 100 mg/mL do extrato puro não foi observado efeito inibitório em ambos os micro-organismos. Entretanto quando em contato com as AgNPs, a concentração inibitória foi de 0,006 mg/mL e 0,1 mg/mL para S. aureus e C. albicans, respectivamente. O efeito citotóxico nas células se comportou de maneira dose-dependente, apresentando maior potencial citotóxico contra a linhagem celular cancerosa HeLa. Conclusão: As AgNPs sintetizadas apresentaram potencial antimicrobiano contra C. albicans e S. aureus, além de baixa atividade contra células normais, indicando sua confiabilidade para aplicação das AgNPs como forma alternativa de tratamento. Estes resultados são promissores e contribuem para pesquisa relacionada à produção de medicamentos utilizando extrato de plantas e metais.

Introduction: In recent years there has been an increase in cases related to infection by Candidaspp. and Staphylococcus spp., as well as the appearance of strains resistant to conventional antibiotics. Nanoparticle biosynthesis consists of the reduction of a metal ion by compounds of natural origin as secondary metabolites of plants and organisms, being the most indicated form because it presents less toxicity when compared to the chemical synthesis. In this way, the biological synthesis is an alternative to obtain new active agents for the treatment of microbial infections. Objective: Synthesize silver nanoparticles from the aqueous extract of Mikania glomerata Sprengel and evaluate possible microbicidal and cytotoxic activity. Material and Methods: For the synthesis of the silver nanoparticles (AgNPs) an aqueous extract of the leaves of Mikania glomerata plus a solution of silver nitrate was used. AgNPs synthesized was evaluated by UV-vis spectrophotometer and FAAS. Furthermore, antimicrobial activity was evaluated against strains of Candida albicans and Staphylococcus aureus and cytotoxicity activity against HeLa and Vero cell lines. Results: AgNPs are shown to be more efficient in combating Candida albicans and Staphylococcus aureusstrains when compared to the pure administered extract. Up to the concentration of 100 mg/mL of the pure aqueous extract no inhibitory effect was observed on both microorganisms. However when the strains were in contact with AgNPs, the inhibitory concentration was 0.006 mg/mL and 0.1 mg/mL for S. aureus and C. albicans, respectively. The cytotoxic effect on the cells behaves in a dose-dependent manner, presenting greater cytotoxic potential against the HeLa cancer cell line. Conclusion: Thus, these results are promising and contribute to research related to the production of drugs using plant extract and metals. The AgNPs synthesized presented the antimicrobial potential against C. albicans and S. aureus, in addition to low activity against normal cells, indicating their reliability for application of AgNPs as an alternative form of treatment.

Antibacterial and antibiofilm activity of carvacrol against Salmonella enterica serotype Typhimurium

ABSTRACT The present study evaluated the antibacterial and antibiofilm activity of carvacrol against Salmonella Typhimurium. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined and the time-kill curve and scanning electron microscopy (SEM) were performed to evaluate antibacterial activity. Antibiofilm activity was evaluated by quantifying total biomass using crystal violet assay, and metabolic activity was determined using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. The action of carvacrol against preformed biofilm on polypropylene and stainless steel was also evaluated by colony counting and SEM. The MIC and MBC was 312 µg mL-1. Carvacrol at MIC and 2 x MIC eliminated cells after 6 and 1 h of treatment, respectively, as exhibited in the time-kill curve. The greatest reduction in biofilm biomass and metabolic activity was 1,719 OD550 and 0,089 OD550 respectively, both at 4 x MIC of carvacrol. In carvacrol treated biofilms of S. Typhimurium on polypropylene, a reduction of 5.12 log was observed with 4 x MIC, while on stainless steel, carvacrol at 4 x MIC reduced bacterial counts by 5 log. The results showed that carvacrol exhibits antibacterial activity and can be used as an alternative for the control of S. Typhimurium biofilms.

Fatores de virulência de Candida spp isoladas de cateteres venosos e mãos de servidores hospitalares / Virulence factors for Candida spp recovered from intravascular catheters and hospital workers hands

Avaliou-se o potencial de virulência de 23 leveduras isoladas de cateteres e mãos de trabalhadores em um hospital do Noroeste do Paraná. As leveduras isoladas de cateter foram mais aderentes e hidrofóbicas (P<0,05) que as leveduras isoladas das mãos. Candida não-albicans expressaram com mais intensidade os fatores de virulência avaliados.

The virulence potential of 23 yeasts recovered from intravascular catheters and the hands of workers in a hospital in the northwestern region of Paraná were evaluated. Yeasts recovered from catheters presented greater adherence and were more hydrophobic (p<0.05) than yeasts recovered from hands. Candida non-albicans species expressed the virulence factors evaluated more intensely.

Produção de biofilme por leveduras isoladas de cavidade bucal de usuários de prótese dentária / Biofilm production by yeasts isolated from bucal cavity of prosthesis wearers

Foi analisada a presença de espécies do gênero Candida na saliva de indivíduos distribuídos em três grupos: 1) com prótese e lesão; 2) com prótese sem lesão; 3) sem prótese e sem lesão, correlacionando com a capacidade de produção de biofilme em meio Sabouraud dextrose, contendo 8 por cento de glicose, sendo determinada por leitura em espectrofotômetro. Dos 220 pacientes foram isoladas 92 leveduras: 24 (grupo 1), 24 (grupo 2) e 44 (grupo 3). Em 70 por cento foi isolado C. albicans e 30 por cento C. não albicans. A produção de biofilme em maior freqüência (64 por cento) foi encontrada entre as leveduras C. não albicans e a maior porcentagem na produção de biofilme, quanto aos grupos de pacientes, foram 75, 63 e 57 por cento correspondendo aos grupos 1, 2 e 3, respectivamente. Esses dados sugerem que a produção de biofilme das espécies do gênero Candida pode estar associada ao processo infeccioso destes isolados