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Primary Care & Walk-In Clinic Providers 

Gina Valente Moore



Dr. Gina has been specializing in gastroenterology, in particular liver disease, for the last 10 years. She obtained her Bachelors of Science in Commerce Marketing in 1991 from Santa Clara University. From there, Dr. Gina studied at Case Western Reserve University in Cleveland Ohio where she obtained her Bachelors of Science in Nursing, Masters of Science in Nursing and her Doctor of Nursing Practice. She then went on to acquire her Post Masters Family Nurse Practioners in 2000 from Sonoma State University in Rohnert Park California.


Dr. Gina is providing comprehensive care to all types of patients here at Mathiesen Memorial Health Clinic.

Kara Sigler FNP, RN, RH


Kara Sigler is a Family Nurse Practitioner offering primary care for all ages. Kara received a Masters in Nursing from the University of California, San Francisco. Previously, Kara worked as a Nurse at a mental health facility for teens. Kara is a Registered Herbalist through the American Herbalist Guild and has had a private practice as well as teaching herbal medicine in the San Francisco Bay Area since 2006. Kara loves to serve the LGBTQQI+ community. Kara grew up in Tuolumne County and has returned to offer integrative care at Mathiesen Memorial as a Nurse Practitioner.

David DeMattei PA-c
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David DeMattei is a Certified Physician Assistant who completed his medical training at Stanford University in Palo Alto, California. Born and raised in Tuolumne County, he worked extensively as an Emergency Medical Technician before pursuing his education at the Stanford School of Medicine. He enrolled at Stanford in hopes of one day bringing his knowledge back to his home town; he is pleased to have accomplished this by joining the team at Mathiesen Memorial Health Clinic. He and his wife live in Sonora; they enjoy hiking, camping, and snowboarding. David looks forward to serving the families of Tuolumne County and seeing patients of all ages.

Melissa Ronneburg, FNP
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Melissa Ronneburg is a family nurse practitioner. She completed her degree at Loma Linda University in Southern California. After finishing school she worked in a very busy asthma and allergy practice. Melissa and her husband moved to Sonora 2003. It did not take long to consider Sonora home. In January 2015 Melissa joined the Mathiesen Memorial Health Clinic family. She is enjoying being back practicing medicine after taking a brief leave of absence while raising her children. In her “spare time”, Melissa is active in her children’s school, soccer and 4-H. The Ronneburg family enjoys camping and fishing in the Sierras.

Kim Schauer PA-c
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Kim Schauer is a certified Physician Assistant, who completed her medical training at the University of Oklahoma in Tulsa, Oklahoma. During her medical training, she received the Bedlam Spirit Award for outstanding achievements in community service. She has spent her career working within community health, helping to improve care for underserved communities. She has practiced in health centers within Oklahoma and Colorado before to moving to Sonora, California. She loves this community and enjoys caring for the people of Tuolumne County. She has experience with all ages. Her specific interests include reproductive health, mental health, addiction medicine, and teen health.

Nate Methot FNP

He completed his graduate training at Samuel Merritt University out of Sacramento in 2015. Prior to this he worked as an RN in both Emergency Medicine and Neuro/Trauma intensive care for 8 years.

He moved to the Sonora area in 2013 to complete his NP training. He has had training in both allopathic medicine and integrative health. In 2019 he pursued extra training in Dermatology and has been seeing Dermatology patients since.

His practice is centered around working with his patients to help reach their health goals together.

Theresa  Sales FNP 

With over thirty years of experience in the medical field, I have attained an extensive understanding of the complexities and nuances of the industry. My academic background includes a Bachelor's Degree in Nursing from Ferris State University and a Master's Degree from Kaplan University. As a Family Nurse Practitioner, I have been practicing for seven years, with a focus on pediatrics for five of those years. Recently, my family and I relocated to Sonora from Michigan, and we are enjoying the sunny California weather. When I am not working, I enjoy exploring nature with my husband and children through various outdoor activities such as hiking.

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