Recovery of Paracoccidioides brasiliensis from a partially calcified lymph node lesion by microaerophilic incubation of liquid media

Abstract

Surgical specimens were obtained from a patient who had had life-threatening paracoccidioidomycosis 5 years previously. Residual lesions were found in the mesenteric lymph nodes; there were areas of caseous necrosis separated from the surrounding tissue by a fibrous capsule made of connective tissue. Abundant P. brasiliensis cells, many of which appeared degenerated, were observed in the necrotic material. Primary isolation was possible only under the microaerophilic conditions offered by fluid media kept stationary at 36°C. Cultures in solid media were obtained after serial passages and gradual accommodation of the strain to aerobic incubation. It is apparent that P. brasiliensis yeast cells can become accustomed to reduced oxygen tension in the tissues. In this way, they are able to withstand the passing of time without completely losing their viability.

Se analizaron muestras quirúrgicas de un paciente que había experimentado paracoccidioidomicosis severa hacía 5 años. Se encontraron lesiones residuales en los ganglios linfáticos mesentéricos, caracterizadas por áreas de necrosis caseosa, separada del tejido circundante por una cápsula fibrosa de tejido conectivo. En el interior de la zona necrotica se hallaron abundantes células de P. brasiliensis, muchas de las cuales estaban degeneradas. El aislamiento fue posible solamente bajo las condiciones de microaerofilia proporcionadas por cultivos liquidos incubado en forma estacionaria a 36°C. La obtención de colonias en medio sólido fue lenta, lográndose solo después de pases repetidos y acomodación gradual a condiciones de aerobiosis. Es evidente que en el interior del tejido las células levaduriformes de P. brasiliensis logran acomodarse a una tensión reducida de oxigeno. En esta forma, pueden soportar el paso del tiempo sin perder por completo su viabilidad.