Newly minted PhD Nikolina Walas plans a career fighting infectious diseases

Dr. Nikolina Walas did not predict that her research path would lead her to spend days studying poop left by both dogs and people on the streets of San Francisco.

But Walas, who earned her PhD in Environmental Health Sciences in May 2025 from UC Berkeley School of Public Health, was curious about the possibility of transmission of antimicrobial resistant E. coli (or AMR-Ec) bacteria between canines and humans on urban sidewalks. This made San Francisco, with its problematic levels of both human and canine feces, a good spot for such a study.

According to the National Institutes of Health, most E. coli strains are harmless, but some can cause infections like diarrhea, urinary tract infections, respiratory illness, pneumonia, and other serious problems. Antimicrobial resistant strains of E. coli are not treatable with drugs, and is an increasing worry to the medical and veterinary world. While investigators initially focused on hospitals as the cause of antibiotic resistance, researchers like Berkeley Public Health’s Jay Graham, are studying environmental spread in animal populations that also receive antibiotics.

In fact, Graham, who is an associate professor in residence of environmental health sciences, supervised Walas and her team. Their paper, published in 2024 in Science of the Total Environment, used bacterial genomics to model the transmission network of AMR-Ec between humans and dogs from feces they collected from the city’s sidewalks.

“Our results provide evidence for multiple sharing events of AMR-Ec between humans and canines, the authors wrote. “In particular, we found one instance of likely transmission from canines to humans, as well as an additional local outbreak cluster consisting of one canine, and one human sample. Based on this analysis it appears that non-human feces act as an important reservoir of clinically relevant AMR-Ec.”

The project became part of her doctoral dissertation, “Population-based studies to characterize antimicrobial resistance dynamics and acquired immunity to Escherichia coli and Shigella.”

Walas earned her master of public health degree in infectious diseases and vaccinology; then switched to environmental health studies for her doctorate. She views the opportunity for interdisciplinary study as one of Berkeley’s strong points.

“I had the unique experience of being in two different departments and doing a master’s program in one department and transitioning into the doctoral program in another department,” Walas said. “I feel like I’ve gotten a good amount of exposure to a lot of different faculty here.

“I just really have enjoyed the interdisciplinary nature of it, where a lot of faculty are familiar with a lot of different topic areas. There’s no really hard line between the different departments – where if you are in a different department they aren’t going to be able to help you. I found a lot of support from different topic areas, which enriches the research that we do and gives you a more well-rounded view.”

Walas came to UC Berkeley after earning an undergraduate degree in microbiology, immunology and molecular genetics at UCLA and then working for BioMarin Pharmaceutical. She worked in the company’s wet lab, on optimization of the BioMarin’s drug purification process for a gene therapy drug.

“I thought that was fascinating as well,” she said. “But I really missed infectious diseases and learning about their impact on the population.”

Walas learned about UC Berkeley’s masters program in infectious diseases through a friend, and decided to apply. She was accepted in February 2020—right as COVID-19 forced much of the world into a shutdown.

“In terms of learning the content of infectious diseases, there were a lot of real life examples,” she said.

Walas made two research trips to Ecuador and also went to Atlanta for a collaboration with the Centers for Disease Control and Prevention.

“I feel like I got a really great exposure to different settings for public health, in the government side and also in international research,” she said. “I want to give a shout out to my advisors Jay Graham and Ben Arnold, because they both have been very strong guiding lights for me during my research, which I really appreciated.”

Walas was able to work closely with Arnold, although he is at UCSF, because of his partnership with Graham. She also appreciates the financial support she received through Arnold’s NIH grant, which covered her tuition, research support, and involvement in the grant’s study based in Ecuador.

Walas plans to take two months off to travel this summer, then continue working on her manuscripts and start job-hunting.

“I’m pretty open to different opportunities,” she said. “I really enjoyed my experience doing hands-on research here, but I think I see myself transitioning more into project management. I would like to stay with infectious diseases. These days, when there’s been a lot of policy oriented toward reducing attention to these topics, I think it’s important to keep pushing for them, they do matter a lot.”