Model of experimental infection in healthy and immunosuppressed swiss albino mice (Mus musculus) using Candida albicans strains with different patterns of enzymatic activity

With the purpose to evaluate Candida albicans virulence in vivo, two strains selected were based on their phospholipase and proteinase activity, and used in a model of experimental infection. One strain, isolated from vaginal secretion, was stocked at the URM Culture Collection for 43 years and presented high phospholipase (Pz=0.217) and proteinase (1.386 U.mL-1) activity. The other strain was a fresh strain isolated from oropharyngeal secretion of an AIDS patient, and presented low phospholipase (Pz=0.482) and proteinase (0.780 U.mL-1) activity. The strains were inoculated via intraperitoneum in immunosuppressed and non-immunosuppressed mice (Mus musculus) and the infection was evaluated over a period of 21 days. Liver, spleen, lungs and kidneys were aseptically removed and the blood of the animals was collected every 72 h. The number of colony forming units (c.f.u) isolated from each organ was counted and a histopathologic examination was performed. The freshly isolated strain was more virulent than the stocked strain, as shown by the number of positive cultures and severity of the lesions observed at the histopathologic examination. A correlation between the in vitro enzymatic activity and the in vivo virulence was not observed. Com o objetivo de avaliar a virulência de Candida albicans in vivo, foram selecionadas duas cepas de acordo com a atividade enzimática de fosfolipase e protease, para utilização em modelo de infecção experimental. Utilizou-se um isolado de secreção vaginal, estocado na Micoteca URM por 43 anos com alta atividade de fosfolipase (Pz=0.217) e de protease (1.386 U.mL-1), e outro recém-isolado de secreção orofaríngea de paciente com AIDS, o qual apresentou baixa atividade de fosfolipase (Pz=0.482) e de protease (0.780 U.mL-1). As amostras foram inoculadas por via intra-peritoneal em camundongos (Mus musculus) na presença e ausência de imunossupressão e a infecção foi avaliada durante 21 dias. A cada 72 h foram assepticamente removidos o fígado, baço, pulmões e rins e coletado o sangue desses animais. Foi quantificado o número de unidades formadoras de colônias (u.f.c.) recuperadas de cada órgão e realizada avaliação histopatológica dos mesmos. A cepa recém-isolada mostrou-se mais virulenta in vivo, quanto ao número de culturas positivas e à severidade das lesões observadas ao exame histopatológico. Não foi observada correlação entre a atividade enzimática in vitro e a virulência in vivo.