Enzymatic characterization of clinical and environmental Cryptococcus neoformans strains isolated in Italy / Caracterización enzimática de aislamientos clínicos y ambientales de Cryptococcus neoformans de Italia

Background. Cryptococcus neoformans is an encapsulated yeast causing mainly opportunistic infections. The virulence factors involved in cryptococcosis pathogenesis include the presence and the size of the polysaccharide capsule, the production of melanin by phenoloxidase, the growth at 37°C and the enzyme secretion like proteinase, phospholipase and urease. Many other enzymes are secreted by C. neoformans but their role in the fungus virulence is not yet known. Aims. In order to investigate this topic, we compared the phospholipase production between strains from patients and from bird droppings, and we examined its relationship to phenoloxidase production. We further characterized the strains by determining the activity of 19 different extracellular enzymes. Methods. Two hundred and five Italian C. neoformans clinical isolates and 32 environmental isolates were tested. Phenoloxidase production was determined by the development of brown colonies on Staib's agar. Extracellular phospholipase activity was performed using the semiquantitative egg-yolk plate method. API ZYM commercial kit was used to observe the production and the activity of 19 different extracellular enzymes. Results. Statistical analysis of the results showed a significantly higher phospholipase activity in the clinical isolates than in the environmental isolates. No significant difference about the phenoloxidase production between both groups was found. Regarding the 19 extracellular enzymes tested using the API ZYM commercial kit, acid phosphatase showed the highest enzymatic activity in both groups. Concerning the enzyme α-glucosidase, the clinical isolates presented a significantly higher positivity percentage than the environmental isolates. A hundred percent positivity in the enzyme leucine arylamidase production was observed in both groups, but the clinical isolates metabolized a significantly greater amount of substrate. Conclusions. The higher phospholipase production in the clinical isolates group confirms the possible role of this enzyme in the cryptococcosis pathogenesis. The extracellular activities of the enzymes acid phosphatase, α-glucosidase and leucine arylamidase, tested by means of the API ZYM commercial kit, appear to be very interesting. Many studies indicate that these enzymes are involved in the virulence of bacteria and parasites; our results suggest their possible role as virulence factors in Cryptococcus infections too (AU)

Antecedentes. Cryptococcus neoformans es una levadura encapsulada que produce infecciones oportunistas. Los factores de virulencia involucrados en la patogénesis de la criptococosis incluyen la existencia y el tamaño de la cápsula polisacarídica, la producción de melanina por medio de la enzima fenoloxidasa, el crecimiento a 37°C y la secreción de ciertas enzimas como proteinasa, fosfolipasa y ureasa. Existen otras enzimas que son secretadas por C. neoformans, pero su papel en la virulencia de este hongo aún no es conocido. Objetivos. Se investigó la producción de fosfolipasa tanto en aislamientos de C. neoformans obtenidos de pacientes como de aislamientos recuperados de deposiciones de aves, y se comparó el grado de producción con el de la síntesis de la enzima fenoloxidasa. Además, distingue las cepas mediante la definición de la actividad de 19 enzimas extracelulares diferentes. Métodos. Se estudiaron 205 aislamientos clínicos de C. neoformans y 32 ambientales. La producción de fenoloxidasa se determinó por el crecimiento de colonias de color marrón en medio de Staib. Para determinar la actividad fosfolipasa extracelular se utilizó el método semicuantitativo en placa con yema de huevo. Con el método comercial API ZYM se determinó la producción de otras 19 enzimas extracelulares. Resultados. El análisis estadístico de los resultados mostró una producción de fosfolipasa significativamente mayor entre los aislamientos clínicos en comparación con los ambientales. No se encontraron diferencias significativas entre ambos grupos en la producción de fenoloxidasa. En lo referente a las 19 enzimas extracelulares valoradas mediante el sistema API ZYM, la fosfatasa ácida mostró la mayor actividad en ambos grupos. Respecto a la enzima α-glucosidasa, nuevamente los aislamientos clínicos presentaron una actividad significativamente mayor. Todos los aislamientos de ambos grupos presentaron actividad leucina-arilamidasa, si bien los aislamientos clínicos procesaron mayor cantidad de sustrato de manera significativa. Conclusiones. La mayor producción de enzima fosfolipasa entre los aislamientos clínicos evidencia que esta enzima puede estar implicada en la patogénesis de la criptococosis. También es interesante la actividad extracelular de las enzimas fosfatasa ácida, α-glucosidasa y leucina-arilamidasa, valorada por medio del sistema comercial API ZYM. Diversos estudios apuntan a que estas enzimas están implicadas en la virulencia de bacterias y parásitos; nuestros resultados muestran también su posible implicación como factores de virulencia en las infecciones por Cryptococcus (AU)

Enzymatic characterization of clinical and environmental Cryptococcus neoformans strains isolated in Italy.

BACKGROUND: Cryptococcus neoformans is an encapsulated yeast causing mainly opportunistic infections. The virulence factors involved in cryptococcosis pathogenesis include the presence and the size of the polysaccharide capsule, the production of melanin by phenoloxidase, the growth at 37°C and the enzyme secretion like proteinase, phospholipase and urease. Many other enzymes are secreted by C. neoformans but their role in the fungus virulence is not yet known. AIMS: In order to investigate this topic, we compared the phospholipase production between strains from patients and from bird droppings, and we examined its relationship to phenoloxidase production. We further characterized the strains by determining the activity of 19 different extracellular enzymes. METHODS: Two hundred and five Italian C. neoformans clinical isolates and 32 environmental isolates were tested. Phenoloxidase production was determined by the development of brown colonies on Staib's agar. Extracellular phospholipase activity was performed using the semiquantitative egg-yolk plate method. API ZYM commercial kit was used to observe the production and the activity of 19 different extracellular enzymes. RESULTS: Statistical analysis of the results showed a significantly higher phospholipase activity in the clinical isolates than in the environmental isolates. No significant difference about the phenoloxidase production between both groups was found. Regarding the 19 extracellular enzymes tested using the API ZYM commercial kit, acid phosphatase showed the highest enzymatic activity in both groups. Concerning the enzyme α-glucosidase, the clinical isolates presented a significantly higher positivity percentage than the environmental isolates. A hundred percent positivity in the enzyme leucine arylamidase production was observed in both groups, but the clinical isolates metabolized a significantly greater amount of substrate. CONCLUSIONS: The higher phospholipase production in the clinical isolates group confirms the possible role of this enzyme in the cryptococcosis pathogenesis. The extracellular activities of the enzymes acid phosphatase, α-glucosidase and leucine arylamidase, tested by means of the API ZYM commercial kit, appear to be very interesting. Many studies indicate that these enzymes are involved in the virulence of bacteria and parasites; our results suggest their possible role as virulence factors in Cryptococcus infections too.