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a Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad Universitaria, Distrito Federal, México b Laboratorio de Soluciones Genéticas, Tijuana, Baja California, México c Unidad Médica de Atención Especializada No. 71, Instituto Mexicano del Seguro Social, Torreón, Coahuila, México d Biotecnología Marina, Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada, Baja California, México e Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey, Nueva Léon, México
Key Words: Coccidioides posadasii • Coccidioides immitis • molecular identification of Coccidioides
Address for correspondence: Laura Rocío Castañón-Olivares, Facultad de Medicina Edificio A 20 piso, Laboratorio de Micología Médica, Ciudad Universitaria, Delegación Coyoacán CP 04510, México D. F. Voice: +52-55-5623-2458 or +52-55-5623-2459; fax: +52-55-5623-2458. lrcastao{at}servidor.unam.mx
Molecular studies of the genome of the fungus Coccidioides have demonstrated two nearly identical, but well-identified species, Coccidioides immitis and C. posadasii, known as "California" and "non-California" species, respectively. The objective of this study was to determine, through molecular methods, whether both species of Coccidioides are present in Mexican patients with coccidioidomycosis and to estimate, their geographical distribution in Mexico. We analyzed 56 clinical isolates of Coccidioides spp. from Mexican patients. Molecular identification of each strain was done by means of real time PCR using TaqMan® probes to amplify single nucleotide polymorphisms (SNPs) in four target sequences, loci, named proline 157, proline 174, hexokinase 149 and glucose-synthase 192. SNP analysis identified two of the 56 isolates as Coccidioides immitis and the remaining 54 as C. posadasii. The dual probe assay that included proline 157, proline 174 and glucose-synthase 192 gave consistent results on SNP differentiation between the two species. In contrast, the template matching hexokinase 149 gave negative results for any species in 34 samples. Our results did not show geographical overlap of the species, and they also confirmed that C. posadasii is the most frequent species in Mexico. A vast majority of C. posadasii strains were localized in the north-central region of the country.
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