About Us

Providers' Bios

biernbaum_Web.jpgROBERT BIERNBAUM, D.O.

Chief Medical Officer, Board Certified in Emergency Medicine

Robert “Rob” Biernbaum, D.O. holds a Master’s degree in Epidemiology from the State University of New York at Buffalo and a Doctorate of Osteopathy from the University of New England.  He completed his Residency in Emergency Medicine at Genesys Regional Medical Center.

In his vital role as Chief Medical Officer, Biernbaum oversees Trillium Health’s expansion as we provide new services, barrier-free access to medical care & supportive services while increasing access to populations with crucial health care needs. His expertise in emergency and trauma-induced care will greatly benefit the patients Trillium Health serves.

Robert joined Trillium from MultiCare Health System, an organization with a fast-paced trauma center, four community hospitals, and many neighborhood clinics based in Tacoma, Washington. Prior to MultiCare, Biernbaum was Rochester Regional Health System’s chief architect for all Epic solutions and in charge of informatics for five hospitals and more than 100 ambulatory sites. He also was the executive responsible for quality measures and meaningful use.

A native Rochesterian with roots in Pittsford & Victor, his expertise will be invaluable to Trillium Health, as the organization continues to focus on the highest quality and affordable healthcare.


WILLIAM M. VALENTI, M.D.William M. Valenti

Senior Vice President for Strategic Advancement, Cheif of Innovation, Co-Founder, and Staff Physician

Dr. Valenti is a graduate of the Medical College of Wisconsin and co-founded Community Health Network in 1989. He is Clinical Associate Professor of Medicine at the University of Rochester School of Medicine and Dentistry and completed his Infectious Diseases training at the University of Rochester. He is a fellow of the Infectious Diseases Society of America. He has been active in HIV-related activities since the early 1980s and is chair of the Infectious Diseases Committee of the Medical Society of the State of New York and is a member of New York State'S Task Force to End the HIV Epidemic by 2020.

He has published more than 150 peer-reviewed articles, book chapters and scientific abstracts on HIV medical care, infectious diseases and health care epidemiology and infection control.

As Chief of Innovation, Dr. Valenti oversees programs to End the HIV Epidemic, including Pre-exposure HIV Prophylaxis (PrEP), LGBTQ Health and the MOCHA Centers.


MICHAEL D. MANCENIDO, D.O.Michael D. Mancenido
Staff Physician

Dr. Mancenido joined the agency in December 2006 as a full-time Spanish-speaking staff physician. After graduating from the University of New England College of Osteopathic Medicine in June 2001, Dr. Mancenido completed both a residency in Internal Medicine and fellowship in Infectious Diseases at the University of Massachusetts Medical School. He is Board Certified in Internal Medicine and Infectious Diseases and is certified as an HIV specialist.

His commitment to increasing health care accessibility for the underserved has led him to pursue several volunteer opportunities. In 2005 Dr. Mancenido spent several weeks in the Dominican Republic helping to create a satellite HIV clinic. Most recently, Dr. Mancenido spent six weeks at the Dessie Regional Referral Hospital in Ethiopia, training local HIV healthcare providers, and offering HIV prevention education to the community.


William Schaefer

WILLIAM SCHAEFER, M.S. RPA-C
Physician Assistant

Mr. Schaefer has been with the agency since 2008 after moving to Rochester from Baltimore, MD. He currently practices medical care under Dr. Roberto Corales, providing comprehensive primary and HIV specialty care.

Mr. Schaefer received his Masters of Science in Physician Assistant Studies at Towson University in Baltimore, MD after receiving his Bachelors of Arts at the State University of New York at Buffalo. He was previously employed as a physician assistant at Chase Brexton Health Services in Baltimore, MD.


DIEGO GRISALES, M.S., F.N.P., B.S.N., R.N.DiegoGrisales_WEB.jpg

Nurse Practitioner

Diego Grisales, NP originally from Medellin, Colombia, he joins Trillium from ElderONE, a geriatric clinic affiliated with Rochester General Health System. He has master’s degree as a nurse practitioner from St. John Fisher College and a bachelor’s degree in nursing from Nazareth College. Diego is originally from Medellin, Colombia.

Grisales is a Family Nurse Practitioner with a specialty in Family medicine, LGBT health care, and HIV prevention. Grisales has experience working in geriatrics and improving health care for migrant workers in the Finger Lakes.



elissa_Hughes_WEB.jpgELISSA HUGHES, F.N.P., B.C., R.N.

Nurse Practitioner

Elissa is a native Rochesterian who has diverse experience as a Registered Nurse and board-certified Family Nurse Practitioner. Her career has ranged from Internal Medicine, Endocrinology, Psychiatry and Hospice. In addition to her Masters of Science in Nursing, she holds a Bachelor’s in English Literature and Technical Writing. Elissa was a National Health Scholar, and her specialty is working with the underserved populations.  She provides primary care and is part of the Care Coordination Team.