[Biological features and experimental pathogenicity of Candida strains isolated by hemoculture at the Hospital Infantil de México "Federico Gómez"].

In a period of 15 months (1990-1991) it was carried out 5781 blood cultures in which 180 strains of yeast-like were isolated. 116 of these strains were selected for biochemical classification, cellular and colonial morphology and experimental determination of virulence in mice. Most of the strains were classified as Candida albicans (60%) and the others were C. tropicalis (15.5%); C. guillermondii (10.3%); T. glabrata (6.8%); Rhodotorula rubra (3.4%); Cryptococcus neoformans (2.58%) y C. parapsilosis (0.86%). C. albicans ATCC14053, y C. tropicalis ATCC14056 and T. glabrata ATCC15545 were employed as controls. The virulence test was performed using mice of 20-30 gr (4-6 weeks age) by intravenous injection in caudal vein with 0.5 ml of different suspension from 10(5) to 10(9) CFU/ml. Observation time was 10 days. Target organ was kidney by macro and microscopic observation of micro-abscess death. LD50 was estimated by the Reed-muench method. Intraspecific and interspecific differences were observed. It is more valid if we take into account that the experiment was done in homogenous population of host without risk factor which influences the human population in hospitals. Experimental virulence was compared with the evolution of diseases in the human host of which the strain was isolated.