“A lot of what he did was create a family,” said Dr. John Stelling, who codirected and cofounded, with Dr. O’Brien, the World Health Organization’s Collaborating Centre for Surveillance of Antimicrobial Resistance. “Everybody contributes their little bit, and their little bit in aggregate tells a lot about emerging threats in close to real time.”
Dr. O’Brien, who had served as the first director of the infectious diseases division at what is now Brigham and Women’s Hospital, died Monday in his Brookline home. He was 95 and his health had been failing. His wife, Ruth Reardon O’Brien, who was the second woman partner at the Ropes & Gray law firm, was 92 when she died Thursday in their home.
“He was one of the very first people to call attention to the risks of antimicrobial resistance developing,” said Dr. Daniel Kuritzkes, chief of the division of infectious diseases at Brigham and Women’s and a professor at Harvard Medical School.
Kuritzkes added that Dr. O’Brien also emphasized the risk of antimicrobial resistance spreading “from person to person, particularly in a health care setting,” and the potential that it “could limit the effectiveness of antibiotics on which we rely to save patients’ lives.”
Along with being an internationally recognized figure in his field, Dr. O’Brien “was a wonderful person to have as a colleague and was extraordinarily modest, given his incredible accomplishments throughout his career,” Kuritzkes said.
With enormous energy that sustained him through a career that spanned more than 60 years at Brigham and Women’s and Harvard Medical School, where he was an associate professor, Dr. O’Brien was 90 when he retired in 2019.
At that point, he was working with Stelling on the WHONET antimicrobial research operation they cofounded. Stelling said WHONET is now in use by more than 3,000 laboratories in more than 130 countries.
He brought the same endless energy to home life in Brookline, where he and Ruth raised their six children.
“Science has said there’s no such thing as perpetual motion, but my father was proof that that was wrong,” said his son Conan O’Brien, the late night TV talk show host and podcaster. “My father was in constant motion. And he was interested in everything — absolutely everything.”
From family to colleagues and friends, Dr. O’Brien “loved making connections with people,” said Justin, the youngest of the O’Brien children.
Reunions, Dr. O’Brien’s or anyone else’s, were always a draw.
“My mother once said she thought he enjoyed her reunions more than she did,” Justin said. “He really loved meeting people and hearing their stories and getting to know them in a very meaningful way.”
A fan and a student of humor who had watched late night talk shows during his years as a medical resident, Dr. O’Brien made sure his children knew comedy’s classics, introducing them to recordings of Jack Benny’s radio shows, Charlie Chaplin movies, and Marx Brothers movies.
“The loudest I’ve ever heard anybody laugh was sitting next to him in a theater watching Peter Sellers in a ‘Pink Panther’ movie,” Conan said.
Anyone who only knew Dr. O’Brien through his work “would think, ‘What a fascinating man,’” Conan said. “But he was often the funniest guy in the room. And when he would laugh, his whole body would convulse and he would almost hug himself.”
The second of three siblings, Thomas Francis O’Brien was born in Worcester on Jan. 28, 1929. He spent his early childhood in Millbury and was in his early teens when his family moved to Southbridge.
His father, Francis Noonan O’Brien, was a banker, and his mother, Gertrude Connor O’Brien, was a homemaker.
Graduating from Mary E. Wells High School in Southbridge in 1946, Dr. O’Brien attended the College of the Holy Cross and received a bachelor’s degree in classics in 1950. He graduated from Harvard Medical School four years later, did his residency at Peter Bent Brigham Hospital, and had an immunology fellowship at Cambridge University in England before serving in the Army Medical Corps for two years in San Antonio.
Two of his Holy Cross classmates were brothers of Ruth Reardon, whom he met when he went to their family’s house one day. They married in 1958.
Other than the Army, Dr. O’Brien spent his medical career at Harvard Medical School and Brigham and Women’s, where he also formerly was director of the microbiology laboratory.
Though Dr. O’Brien was best known for his work in antimicrobial drug resistance, “early in his career, he produced the first device” that allowed patients to undergo hemodialysis more than once using the same vein site, Kuritzkes said in his email to Brigham and Women’s colleagues. That development helped acute renal failure patients undergo hemodialysis more frequently, which improved their health outcomes.
As head of the hospital’s microbiology lab, Dr. O’Brien’s management style reflected his personal approach to learning the personal stories of everyone he met — which meant he even formed a bond with the overnight crew.
“He knew the guy who was there from 11 to 7, five nights a week,” said Holly Bodman, former technical director of the microbiology lab. “He cared about every person individually in that lab. He was an amazing gentleman, a wonderful man.”
In addition to his sons Conan and Justin, Dr. O’Brien leaves two other sons, Neal of Brookline and Luke of Holliston; two daughters, Kate of Boston and Jane of San Anselmo, Calif.; and nine grandchildren.
A funeral Mass for Dr. O’Brien and Ruth Reardon O’Brien will be said at 11 a.m. Wednesday in St. Lawrence Church in Brookline.
When Dr. O’Brien returned from his work-related world travels, Conan said, “he’d come through the door and start making giant meals” for a crowd around the dinner table that often edged into double-digits.
Then he might head off to a marsh, having heard that a rare heron was making a local appearance.
Dr. O’Brien “always said to me, growing up, that if you ever have a chance to do something, do it. It wasn’t much more defined than that,” Justin said. “I think his point was that you’re always going to end up meeting someone or having some kind of adventure and getting something out of whatever you’re doing that will benefit your life.”
Conan said their father “had a voracious appetite for ideas and people and the crazy variety and irony of life. He wanted to go everywhere, meet everybody, see everything, taste everything.”
And that enthusiasm made Dr. O’Brien a favorite of all he met.
“For the rest of my time on earth I will be hearing from people who want to talk with me about my dad,” Conan said. “I’ve never met anyone like him, and he happens to be my father. If I met him randomly in a hotel lobby, I’d think, ‘Who the hell is this guy? He’s the most interesting person I’ve ever met.’ “
Bryan Marquard can be reached at bryan.marquard@globe.com.