Identificación rápida de Histoplasma capsulatum en lisados de cultivo / Rapid identification of Histoplasma capsulatum in culture lysates

Antecedentes. Histoplasma capsulatum es el agente causal de la histoplasmosis, micosis asociada principalmente a pacientes inmunocomprometidos. La rápida identificación del hongo a partir del cultivo permite el tratamiento temprano. Objetivo. Evaluar un sistema de PCR para dos dianas específicas de H. capsulatum en lisados acuosos de cultivos. Métodos. Se utilizaron dos técnicas de PCR previamente descritas que, en reacciones independientes, amplifican fragmentos específicos de 111 y 279 pb del gen AgM de H. capsulatum. Se analizaron 248 cepas de H. capsulatum y 68 de otras especies fúngicas.Para la amplificación se partió de un lisado acuoso (que contenía el ADN), obtenido por tres ciclos de hervido/enfriamiento rápido a 0°C. En casos particulares se obtuvo ADN purificado y/o se secuenció el producto la amplificación. Resultados. Las técnicas de PCR amplificaron las dos bandas a partir del lisado acuoso de 239 cepas de H. capsulatum; las 9 restantes sólo mostraron bandas de amplificación a partir de ADN purificado. No se observó amplificación específica a partir de lisado acuoso ni de ADN purificado de 66 cepas de especies distintas de H. capsulatum. Dos cepas de Emmonsia crescens presentaron ambas bandas de amplificación cuyas secuencias resultaron tener una homología superior al 97% con secuencias de H. capsulatum. El tiempo total de la prueba no superó las 7h con un 96% de sensibilidad, 97% de especificidad y un valor predictivo positivo de 99%. Conclusiones. El método es rápido, económico y puede ser utilizado como una alternativa para identificar presuntivamente H. capsulatum en lisados de cultivo sin purificar(AU)

Background. Histoplasma capsulatum is the agent of histoplasmosis, a deep mycosis mainly afflicting immunocompromised patients. Rapid identification of the fungus isolated from clinical specimens allows timely administration of specific treatment. Aim. To assess the ability of a dual PCR system targeting specific H. capsulatum DNA sites to identify fungal species in simple aqueous lysates from cultured fungi. Methods. We analysed the performance of two independent PCR reactions designed to amplify fragments of 111 and 279bp included in H. capsulatum-specific gene AgM. We used 248 H. capsulatum strains and 68 isolates of other fungal species. Reaction templates consisted of aqueous lysates of cultured fungi (either in mycelial or yeast phase) obtained after three cycles of boiling and immediate cooling at 0°C. Selected strains were submitted to conventional DNA extraction and/or sequencing. Results. Both PCR systems performed identically. Amplification from aqueous lysates was achieved from 239 H. capsulatum strains; the remaining 9 strains only showed specific bands when purified DNA was used as template. Of all other fungal species tested, only 2 Emmonsia crescens strains amplified H. capsulatum-specific bands and sequences of their amplified PCR products matched > 97% with H. capsulatum sequences. Total test time did not exceed 7h with 96% sensitivity, 97% specificity and 99% positive predictive value. Conclusions. The assay is fast, accurate and economical, and can be an alternative method for presumptive identification of H. capsulatum in simple culture lysates(AU)

[Rapid identification of Histoplasma capsulatum in culture lysates]. / Identificación rápida de Histoplasma capsulatum en lisados de cultivo.

BACKGROUND: Histoplasma capsulatum is the agent of histoplasmosis, a deep mycosis mainly afflicting immunocompromised patients. Rapid identification of the fungus isolated from clinical specimens allows timely administration of specific treatment. AIM: To assess the ability of a dual PCR system targeting specific H. capsulatum DNA sites to identify fungal species in simple aqueous lysates from cultured fungi. METHODS: We analysed the performance of two independent PCR reactions designed to amplify fragments of 111 and 279 bp included in H. capsulatum-specific gene AgM. We used 248 H. capsulatum strains and 68 isolates of other fungal species. Reaction templates consisted of aqueous lysates of cultured fungi (either in mycelial or yeast phase) obtained after three cycles of boiling and immediate cooling at 0°C. Selected strains were submitted to conventional DNA extraction and/or sequencing. RESULTS: Both PCR systems performed identically. Amplification from aqueous lysates was achieved from 239 H. capsulatum strains; the remaining 9 strains only showed specific bands when purified DNA was used as template. Of all other fungal species tested, only 2 Emmonsia crescens strains amplified H. capsulatum-specific bands and sequences of their amplified PCR products matched > 97% with H. capsulatum sequences. Total test time did not exceed 7h with 96% sensitivity, 97% specificity and 99% positive predictive value. CONCLUSIONS: The assay is fast, accurate and economical, and can be an alternative method for presumptive identification of H. capsulatum in simple culture lysates.