The microbes that call the New York City subway system home are mostly harmless, but include samples of bacteria that are resistant to drugs and even DNA fragments associated with anthrax and Bubonic plague.
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This is according to a citywide microbiome map published by Weill Cornell Medical College investigators.
The study, published in Cell Systems, demonstrates that it is possible and useful to develop a "pathogen map", PathoMap, of a city, with the heavily traveled subway a proxy for New York's population.
It is a baseline assessment, and repeated sampling could be used for long-term, accurate disease surveillance, bioterrorism threat mitigation, and large scale health management for New York, says the study's senior investigator, Dr. Christopher E. Mason, an assistant professor in Weill Cornell's Department of Physiology and Biophysics and in the HRH Prince Alwaleed Bin Talal Bin Abdulaziz Al-Saud Institute for Computational Biomedicine (ICB).
The PathoMap findings are generally reassuring, indicating no need to avoid the subway system or use protective gloves, Dr. Mason says. The majority of the 637 known bacterial, viral, fungal and animal species he and his co-authors detected were non-pathogenic and represent normal bacteria present on human skin and human body. Culture experiments revealed that all subway sites tested possess live bacteria.
Strikingly, about half of the sequences of DNA they collected could not be identified—they did not match any organism known to the National Center for Biotechnology Information or the Centers for Disease Control and Prevention. These represent organisms that New Yorkers touch every day, but were uncharacterized and undiscovered until this study.
The findings underscore the vast potential for scientific exploration that is still largely untapped and yet right under scientists' fingertips.
"Our data show evidence that most bacteria in these densely populated, highly trafficked transit areas are neutral to human health, and much of it is commonly found on the skin or in the gastrointestinal tract," Dr. Mason says. "These bacteria may even be helpful, since they can out-compete any dangerous bacteria."
But the researchers also say that 12 percent of the bacteria species they sampled showed some association with disease. For example, live, antibiotic-resistant bacteria were present in 27 percent of the samples they collected. And they detected two samples with DNA fragments of Bacillus anthracis (anthrax), and three samples with a plasmid associated with Yersinia pestis (Bubonic plague) both at very low levels.
Notably, the presence of these DNA fragments do not indicate they are alive, and culture experiments showed no evidence of them being alive.
These apparently virulent organisms are not linked to widespread sickness or disease, Dr. Mason says. "They are instead likely just the co-habitants of any shared urban infrastructure and city, but wider testing is needed to determine how common this is in other cities." ■