Dirty money

New research suggests that the bacteria Staphylococcus can survive on euros for extended periods of time, raising concerns over the spread of disease in places such as hospitals

December 12, 2013

Bacteria that can be fatal to hospital patients may be lurking much closer than they think – on the money in their pockets and the hands of their visiting friends and family, according to a recent study by researchers from the Cork Institute of Technology in Ireland. The finding raises concerns about monetary transactions in hospitals and their potential to spread disease.

The study, published in the August issue of the Journal of Applied Microbiology, tested 155 euro bills and coins for the presence of Staphylococcus, a bacteria responsible for a variety of infections ranging from minor skin infections to fatal invasions of the blood, bones or even the heart and lungs. Methicillin-resistant Staphylococcus aureus, or MRSA – a well-known, antibiotic-resistant strain – can be devastating to people with compromised immune systems, especially patients in hospitals.

Out of the tested euros, 97 percent harbored at least one strain of Staphylococcus, with an average of 22.19 bacterial colonies per bill. Sixty-two percent of these strains were resistant to antibiotics. In addition, S. aureus, the same species responsible for MRSA, was capable of surviving on notes for more than 19 days and on coins for more than 16 days.

“[The quantity of Staphylococcus] doesn’t need to be especially high to cause infection, and less so for immunocompromised patients,” said Jim O’Mahony, a professor at Cork specializing in biotechnology and coauthor on the study. The number of individual bacteria in a colony is variable, so it’s difficult to say how many individual Staphylococcus bacteria are present on any given note. Many researchers agree that it takes approximately 100,000 S. aureus bacteria to cause an infection.

Based on the results, O’Mahony believes hospitals should consider eliminating cash transactions altogether, opting instead for alternatives such as Google Wallet, a mobile payment system that allows users to store credit and debit card information on their phones. As cash remains almost universally accepted in medical settings, his proposal would mean a radical change for hospitals.

But some researchers doubt that the presence of cash in hospitals has any impact on the rate of staph infections there. Paul Fey, specialist in staphylococcal research at the University of Nebraska, said he was concerned the results could be taken out of context. “The fact is that regardless of whether we have money or not, we’re still going to be transferring S. aureus around all the time,” he said. “Whether or not having the money in the hospital is going to decrease rates of infection – I doubt it.”

Sandra Hensley, a researcher from the University of Toledo who has conducted studies on Staphylococcus in hospital rooms, has some reservations about eliminating cash transactions in hospitals. She thinks cashless alternatives could still pose an infection risk. “What I see in the cafeteria now is people using their [credit] cards,” she said. “So, you know, we’re replacing [cash] with a card, there’s a larger contamination surface” – the surface area available on an object for bacteria to colonize – “and they put that card back in their pocket.”

In spite of these doubts, O’Mahony said the results of the study should not be ignored. “We have shown that up to 97 percent of notes are contaminated by staph,” he said. “I’m not sure how you can make the argument that removing cash from hospitals will not help in reducing infection transmission.”

About the Author

Chelsea Harvey

Chelsea Harvey is a recent graduate of Auburn University, where she received a B.S. in zoology, as well as minors in English and Spanish. Unable to choose between her love of science and her love of writing, she spent most of her free time as an undergrad working for her campus newspaper while simultaneously memorizing hundreds of scientific names for class. Outside of SHERP, her interests include playing music with friends, traveling and keeping up with international affairs.


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