Detection of C. immitis in Soil and Dust Samples from the Southern San Joaquin Valley, Kern County, CA

Undergraduate #120
Discipline: Biological Sciences
Subcategory: Microbiology/Immunology/Virology

Alex Valenzuela - California State University Bakersfield
Co-Author(s): Antje Lauer, California State University Bakersfield, Bakersfield, CA

Coccidioidomycosis is a disease caused by a dimorphic fungal pathogen that is endemic to the Southwestern United States, Mexico, parts of South America and Northern China. The pathogen poses a risk to several groups of people, including construction and agricultural workers, as well as immunocompromised people. Coccidioides immitis is one the two fungal pathogens responsible for coccidioidomycosis. C. immitis primarily lives in semiarid soils from desert regions. Arthrospores of the pathogen can become airborne when soil is disturbed and when inhaled can result in mycosis of the lungs and other parts of the body. Incidence of coccidioidomycosis in California is highest in Kern County, which is known for its poor air quality due to its geographic location, intense agriculture, increase in construction and effects of the ongoing drought. The pathogen has been frequently detected in soils collected in Kern County, and therefore we hypothesize that it should be found in dust samples as well. Dust was collected from various locations in Taft, CA between October and December 2015 using a ChemVol sampler. DNA was extracted from a total of twelve samples and investigated via nested PCR methods to detect the pathogen (Baptista-Rosas et al. 2012 and Vargas-Gastélum et al. 2015). In addition, we obtained fingerprints of the fungal communities in the dust samples by using Denaturing Gradient Gel Electrophoresis (DGGE) with 18S rDNA amplicons. Individual DGGE bands were excised and re-amplifed, then sequenced. DNA from Ascomycetes and Basidiomycetes was found in all DNA dust samples. Overall, DGGE fingerprints indicated a low fungal diversity in all dust samples. Fungi from the following orders were detected so far: Entomophtorales, Capnodiales, and Helotiales. However, C. immitis was not detected in any of the samples with any of the methods pursued. Future research will focus on identifying all fungal and bacterial species in the collected dust samples and additional dust samples will be collected at different times of the year.

References: Baptista-Rosas RC, Catalan-Dibene J, Romero-Olivares AL, Hinojosa A, Cavazos T, Riquelme M. Molecular detection of Coccidioides spp. from environmental samples in Baja California: linking Valley Fever to soil and climate conditions. Fungal Ecology. 2012 Apr 30;5(2):177-90.
Vargas- Gastélum L, Romero-Olivares AL, Escalante AE, Rocha-Olivares A, Brizuela C, Riquelme M. Impact of seasonal changes on fungal diversity of a semi-arid ecosystem revealed by 454 pyrosequencing. FEMS microbiology ecology. 2015 May 1;91(5):fiv044.

Funder Acknowledgement(s): Keith Bein, Kent Pinkerton, and Stephen McCurdy of UC Davis (Grant # 1U01OH010839) CSU Bakersfield Louis Stokes Alliances for Minority Participation (LSAMP) program. CSU Bakersfield Louis Stokes Alliances for Minority Participation (LSAMP) program

Faculty Advisor: Antje Lauer, alauer@csub.edu

Role: DNA extraction; Nested polymerase chain reactions (PCR); Agarose gel electrophoresis; Denaturing gradient gel electrophoresis (DGGE). Agarose gel electrophoresis Denaturing gradient gel electrophoresis (DGGE)