Phillip Tarr, MD, is a busy investigator juggling meetings, research, teaching and patient care. And he is a man driven to find answers to fight deadly diseases in newborns.

As a child, Tarr loved reading about microbe hunters who worked in the early 1900s. As a biology major at Brown University, he first became a microbe hunter himself, getting involved in research projects directed at infectious diseases.

“In bacterial research, you can grow the germs easily and get answers relatively quickly,” says the Washington University pediatric gastroenterologist at St. Louis Children’s Hospital. “That really appealed to me. You don’t have to wait.”

Tarr’s interest in finding causes behind gastrointestinal infections was piqued while a resident in Seattle at the University of Washington School of Medicine and Seattle Children’s Hospital. Of the children with bloody diarrhea that often came to the hospital, about 10 percent developed hemolytic uremic syndrome, a disorder that occurs when an infection in the digestive system produces toxins that destroy red blood cells, leading to kidney injury or failure.

“One child would get it and get better, but a sibling would get it and go on to kidney failure,” Tarr says. “This had to have been an infection. I was determined to find the pathogen.”

During his 23 years at the University of Washington, Tarr and his research team discovered that E. coli O157:H7, a strain that can produce potentially lethal toxins, was the principal cause behind hemolytic uremic syndrome in these children. Other researchers had identified this pathogen in the early 1980s, but this research established the bacteria is the predominant cause of hemolytic uremic syndrome in the United States.

“With the right environment and collaborators, you learn a lot from your patients, and the best science is built on real problems and powerful technology,” Tarr says. “That lesson has stuck with me, and I’m trying to apply it here.”

Tarr joined the faculty at Washington University School of Medicine in St. Louis in 2003 as the director of pediatric gastroenterology and nutrition and received the Melvin E. Carnahan Professorship in Pediatrics in 2004. He also has a joint appointment in molecular microbiology and is the co-leader of the pathobiology research unit in the Department of Pediatrics.

“There are very few places in the world where pediatric gastroenterologists can combine investigative interests with outstanding microbiology and genomics,” he says. “When the opportunity arose to move, it was a convergence of a great environment, a great position and wanting to expand my research interests.”

“Phil Tarr is a very creative and accomplished clinical and translational investigator both in infectious disease and gastroenterology,” says Alan L. Schwartz, PhD, MD, the Harriet B. Spoehrer Professor and head of the Department of Pediatrics. “He had the foresight to realize the synergies in this area long before others. It is our great good fortune to have him here at Washington University.”

Looking for answers

During his tenure at WUSTL, Tarr has teamed with faculty from various departments to study necrotizing enterocolitis, a devastating disorder in premature infants that causes the death of tissue in the lining of the intestinal wall. The syndrome occurs in up to 10 percent of premature infants and is fatal about 25 percent to 35 percent of the time.

“The percentage of premature babies who get necrotizing enterocolitis and the percentage of children who die has not budged for 30 years,” Tarr says. “This is an awful disease that is understudied. It also is plausibly related to microbes in the gut.”

Treatment for milder cases of necrotizing enterocolitis includes temporarily withholding food from the child and observation. In more severe cases, surgery to remove the small bowel or colon is the only option. While researchers aren’t sure what causes the disorder, Tarr says circumstantial evidence shows gut microbes play a role.

To find the answers, he has teamed with Barbara Warner, MD, professor of pediatrics, and Brad W. Warner, MD, the Jessie L. Ternberg, MD, PhD, Distinguished Professor of Pediatric Surgery in Surgery and pediatric surgeon-in-chief at St. Louis Children’s Hospital, both specialists on necrotizing enterocolitis. Barbara Warner studies the effect of the neonatal microbiome on health and disease, including on necrotizing enterocolitis in conjunction with Tarr, and Brad Warner performs the surgeries.

Barbara Warner says Tarr is a brilliant researcher.

“I think the most predominant, most significant component of his personality is that he’s very genuine, and he really reaches out to help others,” she says. “From a mentoring standpoint, one of his strongest points is his investment and willingness to put himself aside and bring forward people who are starting their careers.”

A team effort

In addition, Tarr works closely with George Weinstock, PhD, professor of genetics and of molecular microbiology at The Genome Institute; Erica Sodergren, PhD, research associate professor of genetics; and William Shannon, PhD, associate professor of biostatistics in medicine and of biostatistics. The group has a four-year grant from the National Institute of Allergy and Infectious Diseases of the National Institutes of Health to study whether necrotizing enterocolitis is linked to microbes in the intestinal tract.

The researchers are collecting fecal samples from premature babies to identify and quantify differences between the microbial communities of the infants who develop the illness and those who do not. This information may provide a foundation for developing ways to prevent or cure the illness.

“We’re trying to get the cohort of at-risk babies together, get specimens and identify the population of bacteria, viruses and genes and how the child is responding,” he says.

So far, the team has more than 200 children enrolled in the study and more than 25,000 specimens carefully barcoded in freezers.

Their goal is to provide hope for children with necrotizing enterocolitis.

“We are looking for one or more detectable changes in the gut that herald or even lead to the development of necrotizing enterocolitis,” Tarr says. “We want to detect these changes and ideally, prevent or better treat the disease.”

Tarr credits the families of the affected babies for their contributions to the study.

“They are the real unsung heroes,” he says. “They have graciously allowed their children to take part in the study. The nurses in the NICU (neonatal intensive care unit) and our laboratory and clinical research team are critical to our success. This is not my project — this is a team effort.”

Working as a team is one of the things he appreciates about WUSTL.

“Collaboration is part of the DNA of this place,” he says. “There are really no barriers.”

Tarr also says training young people is another part of the School of Medicine’s ethos.

“It’s not just lip service — it really is a major part of our job description in everything we do.”

Fast facts about Phillip Tarr

Title: The Melvin E. Carnahan Professor of Pediatrics; director of the Division of Pediatric Gastroenterology and Nutrition in the Department of Pediatrics
Family: Wife, Diane, a consultant and nutritionist; sons Ian, 16, and Jake, 14
Hobbies: Cycling in Forest Park or the Katy Trail, hiking