National production of certified reference fungal cultures / Producción nacional de cultivos fúngicos de referencia certificados

Reference fungal cultures (RFCs) are essential for the internal quality control of laboratories. The production of these cultures requires standardized procedures (IRAM 14950:2016 and ISO 17034:2016 standards) carried out by a recognized and accredited laboratory. The aim of this work was to produce RFC in paper disks of autochthonous strains, characterized by two, homogeneous and stable reference methods traceable at species level. RFC were produced using 14 regional species (7 yeasts and 7 filamentous fungi) from the fungal culture collection (DMic). Paper disks were impregnated with a culture suspension, dried and packed. Homogeneity, viability, identity and purity were verified. Short-and long-term stability at different temperatures and storage times were studied. Characterization of each strain allowed to confirm its identity and to ensure its traceability at international level. Produced batches were homogeneous and stable at -20 ±5 °C for 30 months. This method of production was adequate to produce homogeneous and stable RFC with phenotypic and genotypic characteristics correctly defined and internationally traceable. Standardized procedures were developed for the production of certified RFC that could be transferred to other microorganisms. Providing RFC that represent regional strains allows laboratories to produce more reliable results with a favorable impact on medical diagnosis, the environment or the food industry.

Los cultivos microbianos de referencia (CR) son imprescindibles para el control de calidad interno de los laboratorios. Asegurar su producción requiere de procedimientos estandarizados (IRAM 14950:2016 e ISO 17034:2016) realizados en un laboratorio reconocido y acreditado. El objetivo de este estudio fue producir cultivos fúngicos de referencia en discos de papel, a partir de un panel de cultivos autóctonos caracterizados por dos métodos de referencia, trazables a nivel taxonómico de especie, homogéneos y estables. Se produjeron CR de 14 especies circulantes en Argentina (7 de levaduras y 7 de hongos miceliales), depositadas en la colección de hongos de interés médico (DMic). Los discos de papel fueron embebidos con una suspensión del cultivo por producir, secados y envasados. Se verificó la homogeneidad, viabilidad, identidad y pureza de cada lote. Se evaluó la estabilidad a corto y largo plazo a distintas temperaturas y tiempos de almacenamiento. La caracterización de cada CR nos permitió confirmar su identidad y asegurar su trazabilidad a nivel internacional. Los lotes producidos fueron homogéneos y estables durante 30 meses conservados a -20 ±5 °C. Este método resultó adecuado para producir CR homogéneos y estables, con características fenotípicas y genotípicas correctamente definidas y trazables a nivel internacional. Los procedimientos estandarizados desarrollados en este trabajo pueden ser transferidos para producir CR certificados de otros microorganismos. La provisión de CR que represente cepas regionales permite a los laboratorios producir resultados más confiables con un impacto favorable en el diagnóstico médico, los estudios ambientales y la industria alimenticia.

First bloodstream infection due to Prototheca zopfii var. hydrocarbonea in an immunocompromised patient.

Here we describe a bloodstream infection due to P. zopfii var. hydrocarbonea in a patient with acute lymphoblastic leukemia. Identification was performed by DNA sequencing of the D1/D2 domain of 26s ribosomal DNA and by MALDI-TOF MS technique. Antifungal susceptibility tests against amphotericin B, fluconazole, itraconazole, and voriconazole showed the following MIC values, respectively: 0.25 mg/L, 128 mg/L, 0.064 mg/L, and 0.125 mg/L. The patient received amphotericin B treatment with a successful outcome.

National production of certified reference fungal cultures.

Reference fungal cultures (RFCs) are essential for the internal quality control of laboratories. The production of these cultures requires standardized procedures (IRAM 14950:2016 and ISO 17034:2016 standards) carried out by a recognized and accredited laboratory. The aim of this work was to produce RFC in paper disks of autochthonous strains, characterized by two, homogeneous and stable reference methods traceable at species level. RFC were produced using 14 regional species (7 yeasts and 7 filamentous fungi) from the fungal culture collection (DMic). Paper disks were impregnated with a culture suspension, dried and packed. Homogeneity, viability, identity and purity were verified. Short- and long-term stability at different temperatures and storage times were studied. Characterization of each strain allowed to confirm its identity and to ensure its traceability at international level. Produced batches were homogeneous and stable at -20±5°C for 30 months. This method of production was adequate to produce homogeneous and stable RFC with phenotypic and genotypic characteristics correctly defined and internationally traceable. Standardized procedures were developed for the production of certified RFC that could be transferred to other microorganisms. Providing RFC that represent regional strains allows laboratories to produce more reliable results with a favorable impact on medical diagnosis, the environment or the food industry.

Candida glabrata species complex prevalence and antifungal susceptibility testing in a culture collection: First description of Candida nivariensis in Argentina.

The presence of the cryptic species belonging to the Candida glabrata complex has not been studied in Argentina. We analyzed a collection of 117 clinical isolates of C. glabrata complex belonging to a National Culture Collection of Instituto Nacional de Microbiología "Dr. Carlos G. Malbrán" from Argentina (40 isolates from blood samples, 18 from other normally sterile sites, 20 from vagina, 14 from urine, 7 from oral cavity, 3 from catheter, 1 from a stool sample and 14 isolates whose clinical origin was not recorded). The aims of this work were to determine the prevalence of the cryptic species Candida nivariensis and Candida bracarensis and to evaluate the susceptibility profile of isolates against nine antifungal drugs. Identification was carried out by using classical phenotypic tests, CHROMagar™ Candida, PCR and MALDI-TOF. The minimal inhibitory concentrations of amphotericin B, 5-fluorocytosine, fluconazole, itraconazole, voriconazole, ketoconazole, posaconazole, caspofungin and anidulafungin were determined according to the EDef 7.3 (EUCAST) reference document. Of the 117 isolates, 114 were identified as C. glabrata and three as C. nivariensis by using PCR and MALDI-TOF. There were no major differences between C. nivariensis and C. glabrata susceptibility profiles. No resistant strains were found to echinocandins. We have found that the percentage of C. nivariensis in our culture collection was 2.56. This is the first description of C. nivariensis in Argentina, and data obtained could contribute to the knowledge of the epidemiology of this cryptic species.

Amino acid substitution in Cryptococcus neoformans lanosterol 14-α-demethylase involved in fluconazole resistance in clinical isolates.

The molecular basis of fluconazole resistance in Cryptococcus neoformans has been poorly studied. A common azole resistance mechanism in Candida species is the acquisition of point mutations in the ERG11 gene encoding the enzyme lanosterol 14-α-demethylase, target of the azole class of drugs. In C. neoformans only two mutations were described in this gene. In order to evaluate other mutations that could be implicated in fluconazole resistance in C. neoformans we studied the genomic sequence of the ERG11 gene in 11 clinical isolates with minimal inhibitory concentration (MIC) values to fluconazole of ≥16µg/ml. The sequencing revealed the G1855A mutation in 3 isolates, resulting in the enzyme amino acid substitution G484S. These strains were isolated from two fluconazole-treated patients. This mutation would not intervene in the susceptibility to itraconazole and voriconazole.