Toxic thermoresistant metabolites of Fusarium oxysporum are capable of inducing histopathological alterations in Wistar rats

The genus Fusarium is known to produce mycotoxins that cause fusariosis in plants, animals and humans. Mycotoxins are among the virulence factors of this genus. Metabolic extracts of Fusarium oxysporum, isolated from a patient with onychomycosis and sterilized by filtration or autoclave, were inoculated intradermally into Wistar rats at concentrations of 0.25, 0.5 and 1 µg/µL, and the effects on their tegument were observed at 24 and 72 hours. After histological procedures and staining by hematoxylineosin, the sections were studied for their inflammatory-reaction intensity and for evidence of injury and tissue distortion. Inflammatory reactions in the dermis and the subcutaneous tissue were observed at all concentrations of the inoculated extract tested. There was a significant influx of neutrophils, mastocytes and lymphocytes, as well as a large quantity of macrophages. Apoptotic bodies and hyperemic blood vessels were observed. This reaction was directly related to the extract concentration, and was most intense in animals that received the 1 mg/µL dose. The maximum peak was observed at 24 hours. The autoclaved metabolic extract produced the same effects as the untreated one, indicating the presence of heat-resistant metabolites. In conclusion, the metabolic extracts obtained from sterilized culture filtrates of F. oxysporum are capable of inducing an inflammatory response within 24 hours in the dermis and subcutaneous tissue of rats.(AU)

Aumento da virulência de Candida albicans após tratamento de quimioterapia / Increased virulence of Candida albicans after antineoplastic chemotherapy

Although yeasts of the genus Candida are part of the normal human oral microbiota, in cancer patients they may be associated with invasive fungal infections. Antineoplastic therapy, with its adverse side effects, increases the likelihood of such infection. One of the important virulence factors is the capacity of yeast cells to adhere to the surface of medical devices inserted into patients. In this study, we tested the in vitro adhesive and film-growing capacity of four Candida albicans samples, isolated before and during chemotherapy from the oral cavity of a patient with adenocarcinoma. Adherence to the orotracheal tube (OTT) and biofilm production were assessed spectrophotometrically and the amount of film growth was estimated by measuring fungal metabolism. Also, the frequency and size of germ tubes were evaluated. The results showed a significant increase in the germ tube size of C. albicans and also an increase in yeast adherence to the OTT after the start of chemotherapy with mitoxantrone.

Embora as leveduras do gênero Candida pertençam a microbiota humana oral normal, em pacientes com câncer a sua presença pode estar associada a infecções fúngicas invasivas. O tratamento quimioterápico, com seus efeitos colaterais, aumenta as chances desta possibilidade. Um dos principais fatores de virulência consiste na capacidade das leveduras de se aderirem a superfície de instrumentos médicos inseridos nos pacientes. O presente estudo avaliou a capacidade in vitro de quatro isolados de Candida albicans, obtidos antes e após o início da quimioterapia de um paciente com adenocarcinoma. Estudos de adesão a tubo endotraqueal; produção de biofilme e quantificação por meio do metabolismo fúngico pelo XTT; frequência e tamanho de tubos germinativos foram realizados. Os resultados demonstraram aumento significante no tamanho do tubo germinativo, assim como o aumento da aderência dessas leveduras ao tubo endotraqueal após o início da quimioterapia com mitoxantrone.

Avaliação das atividades antimicrobiana, citotóxica, moluscicida e antioxidante de Bromelia antiacantha Bertol: (Bromeliaceae) / Evaluation of antimicrobial, cytotoxic, molluscicidal and antioxidant activities of Bromelia antiacantha Bertol: (Bromeliaceae)

A Bromelia antiacantha Bertol. (Bromeliaceae), conhecida como gravatá ou caraguatá, apresenta características medicinais, alimentícias e ornamentais. Neste trabalho foram avaliadas as atividades antifúngica, antibacteriana, citotóxica, moluscicida e antioxidante de extratos alcoólicos das folhas e frutos desta espécie. Na avaliação da atividade antimicrobiana pelo método de microdiluição os extratos alcoólicos não foram eficientes frente à cepa referência do fungo Candida albicans (ATCC 90028), cepas clínicas de C. albicans e C. glabrata, e frente às bactérias S. aureus (ATCC 6538), P. aeruginosa (ATCC 9027) e E. coli (ATCC 8739). A atividade citotóxica, avaliada pelo bioensaio de toxicidade sobre náuplios de Artemia salina Leach (TAS), foi positiva para ambos extratos, com valores de DL50 variando em torno de 620 µg mL-1 e 360 µg mL-1, para os extratos alcoólicos dos frutos e das folhas, respectivamente. A atividade moluscicida, avaliada frente a caramujos da espécie Biomphalaria glabrata (Molusca, Gastropoda), não mostrou toxicidade aguda para soluções de 400 µg mL-1. As propriedades antioxidantes dos extratos investigadas in vitro mediante o método de DPPH• foram consideradas modestas (~ 35 por cento de inibição na concentração de 1000 µg mL-1). Dentre as atividades biológicas que foram testadas a atividade citotóxica foi a mais pronunciada.

Bromelia antiacantha Bertol. (Bromeliaceae), popularly known as "gravatá" or "caraguatá", shows medicinal, nutritional and ornamental properties. In the present study, the alcoholic extracts of leaves and fruits of this species were evaluated for antifungal, antibacterial, cytotoxic, molluscicidal and antioxidant activities. The alcoholic extracts evaluated by microdilution method were not efficient against the standard strain of Candida albicans (ATCC 90028), clinical strains of C. albicans and C. glabrata, and S. aureus (ATCC 6538), P. aeruginosa (ATCC 9027) and E. coli (ATCC 8739). The cytotoxic activity evaluated by toxicity bioassay on nauplii of Artemia salina Leach (TAS) was positive for both extracts, with LD50 values ranging around 620 µg mL-1 and 360 µg mL-1 for alcoholic extracts from leaves and fruits, respectively. The molluscicidal activity evaluated against Biomphalaria glabrata (Mollusca, Gastropoda) did not present acute toxicity for 400 µg mL-1 solutions. The antioxidant properties of the extracts investigated in vitro using the DPPH• method were considered modest (~ 35 percent of inhibition at 1000 µg mL-1). Among the evaluated biological activities, cytotoxic activity was the most marked.

Atividade hemolítica e produção de tubos germinativos relacionados ao potencial patogênico de isolados clínicos de Candida albicans / Hemolytic activity and production of germ tubes related to pathogenic potential of clinical isolates of Candida albicans

We assessed the virulence factor profile and in vitro antifungal susceptibility of 27 hospital isolates of C. albicans; 19 of these were from infections (16 urinary and three blood), and the other eight were isolated from sites of colonization (two from hands of health professionals, and six from central venous catheters). The virulence factors assayed were germ tube formation and production of extracellular products (hemolysins, proteinases, and phospholipases). Susceptibility to fluconazole, itraconazole, voriconazole and amphotericin B was determined by E-test. Regarding the virulence factors, the infection isolates produced significantly more hemolysin and germ tubes than the colonization isolates (p<0.05). There were no significant differences in the production of other factors between isolates from the two sources (p>0.05). Amphotericin B showed the lowest minimum inhibitory concentrations for all the isolates. The highest resistance was observed for the azoles, especially in the clinical isolates. These results suggest that the capacity of C. albicans to produce hemolysins and germ tubes may be associated with its pathogenic potential. Colonization isolates may pose a high risk of nosocomial infection, especially when the yeasts show resistance to antifungals.

O perfil de virulência e o de susceptibilidade in vitro aos antifúngicos de 27 amostras de C. albicans de origem hospitalar foi avaliado, sendo que 19 delas foram isoladas de infecções (16 urinárias e três sanguíneas) e as outras oito foram isoladas de colonização (duas de mãos de profissionais da saúde e seis de cateter venoso central). Os seguintes fatores de virulência foram investigados: formação de tubo germinativo e produção de compostos extracelulares (hemolisinas, proteinases e fosfolipases). Suscetibilidade ao fluconazol, itraconazol, voriconazol e anfotericina B foram determinadas por E-test. Em relação aos fatores de virulência, os isolados de infecção produziram significativamente mais hemolisina e tubos germinativos do que os de colonização (p<0.05). Não houve diferença significativa na produção das outras enzimas, entre os isolados das duas fontes (p>0.05). Anfotericina B mostrou as menores concentrações inibitórias mínimas para todos os isolados. Maiores índices de resistência foram observados aos azólicos, especialmente entre os isolados clínicos. Estes resultados sugerem que a capacidade de C. albicans produzir hemolisinas e tubos germinativos pode estar associada com seu potencial patogênico. Por outro lado, leveduras em colonização podem oferecer alto risco para infecção hospitalar, especialmente quando têm perfil de resistência aos antifúngicos.

Radiotherapy effect on frequency of Candida spp. and on virulence of C. albicans isolated from the oral cavity of head and neck cancer patients

The aim of this study was to investigate the diversity and prevalence of yeasts, and the virulence of C.albicans found in the oral cavity during the course of ionizing radiation treatment of patients with head and neck tumor (HNTP). Samples from 21 HNTP and 24 healthy controls were isolated and identified. C. albicans isolated from two patients during radiotherapy were analyzed for virulence factors. Radiotherapy induced a higher level of both yeast colonization (81% vs 33%) and non-albicans Candida (NAC) colonization (52.4% vs 4.0%) in HNTP than the control group. Patients were colonized by 5 different NAC species: C. glabrata, C. tropicalis, C. parapsilosis, C. krusei and C. kefir. On the other hand, C. albicans colonization was similar in patients and controls (6/21, 28.6% vs 7/24, 29.2%, respectively). Also, of the 11 patients assessed before and during radiotherapy, 5 (45.5%) were colonized before the start of treatment and another 5 (45.5%) during treatment. All of the latter were colonized by NAC species alone. Moreover, we observed a significant and continuous enhancement of C. albicans virulence as the radiotherapy progressed, in the two patients involved in this test. Thus, it is concluded that radiotherapy is an important predisposing factor for the oral candidiasis, including NAC species. Also, it may facilitate the development of more virulent C. albicans strains.

O objetivo deste estudo foi avaliar a diversidade e a prevalência de Cândida, bem como a virulência de Cândida albicans, isoladas da cavidade bucal no decurso de tratamento por radiações ionizantes de pacientes acometidos por tumores de cabeça e pescoço (PTCP). Amostras de 21 pacientes e 24 controles foram analisadas. C. albicans isoladas de dois pacientes ao longo do tratamento radioterápico foram avaliadas para fatores de virulência. A radioterapia induziu um grande aumento da colonização de Cândida como um todo (81% vs 33%) e Cândida não albicans (CNA) em particular (52.4% vs 4.0%) em PTCP quando comparado com controles não irradiados. Cinco espécies diferentes de CNA foram encontradas nos pacientes: C. glabrata, C. tropicalis, C. parapsilosis, C. krusei and C. kefir. Por outro lado, a colonização por C. albicans nestes pacientes e controles foi similar (6/21, 28.6% vs 7/24, 29.2%, respectivamente). Além disso, dos 11 pacientes que foram avaliados antes e durante o tratamento radioterápico, 5 pacientes (45,5%) foram colonizados antes do início da radioterapia e outros 5 (45,5%) durante o tratamento radioterápico. Destes últimos, todos foram colonizados apenas com espécies CNA. Observou-se, ainda, um aumento contínuo e significante da virulência de C. albicans com o progresso da radioterapia nos dois pacientes estudados. Conclui-se que o tratamento radioterápico é um importante fator de desenvolvimento de candidíase oral, incluindo candidíase por espécies não albicans, em pacientes portadores de tumor de cabeça e pescoço. A radioterapia pode, ainda, facilitar o desenvolvimento de cepas mais virulentas de C.albicans.

A medium for inducing conversion of Histoplasma capsulatum var. capsulatum into its yeast-like form

Histoplasma capsulatum var. capsulatum is a dimorphic fungus that, under special conditions, converts from its more common mycelial form to a yeast-like form. Achieving this conversion, however, has been problematical for researchers. The present study tested conversion rates in ten Histoplasma capsulatum var. capsulatum strains using seven culture media, four of wich were conventional and three novel. One of our novel media, MLGema, induced complete conversion, of two strains within five days of incubation at 35 degrees centigrades, and of all strains that eventually converted by the time of the second subculturing transfer, under defined experimental conditions. MLGema is also inexpensive and easy to produce