Rev Iberoam Micol
2008; 25:27-31.
Urease activity in Cryptococcus neoformans and Cryptococcus gattii
Josep M. Torres-Rodríguez1, Eidi Alvarado-Ramírez1 & Ricardo Gutiérrez-Gallego2
1Unidad de Investigación en Enfermedades Infecciosas y
Micologia. Institut Municipal d' Investigació Mèdica,
Unidad Docente del Instituto Municipal de Asistencia Sanitaria,
Unversitat Autònoma de Barcelona;
2Departamento de Investigación de Ciencias de la Salud,
Universitat Pompeu Fabra, Barcelona, España
Urease is an enzyme considered one of the main virulence factors in
Cryptococcus neoformans. Quantitative differences in urease production
between C. neoformans and the new species Cryptococcus gattii have not
been so far documented. Using a standardized method, 25 isolates of C.
neoformans and 19 of C. gattii were seeded in Christensen urea broth
medium for urease activity detection. Approximately, the 50% of
activity of one unit of commercial jack beans urease (A550 = 0.215) was
considered
as a reference to classified the Cryptococcus in two cathegories, low
(A550
< 0.215) or high (A550 0.215) urease producers. After 72 hours of
incubation,
76% of C. neoformans and 15.8% of C. gattii strains were high urease
producers (p = 0.016). Based on these results, the species C.
neoformans appeared
as the highest urease producer. Other virulence factors should also be
investigated to explain C. gattii pathogenicity.
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