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You have dirty money in your wallet

According to a new study, dirty money takes on a whole new meaning when examined for bacteria
According to a new study, dirty money takes on a whole new meaning when examined for bacteria
Robin Wulffson, MD

According to a new study, dirty money takes on a whole new meaning when examined for bacteria. Paper money is one of the most frequently passed items in the planet. The unpublished study was described in the April 21 edition of The Wall Street Journal. It was conducted by researchers at New York University.

The study dubbed, New York University's Dirty Money Project, was described by the authors as the first comprehensive study of the DNA on $1 bills. They found that currency is a medium of exchange for hundreds of different kinds of bacteria as bank notes are passed from hand to hand. They analyzed the genetic material on $1 bills and identified 3,000 types of bacteria; they note that the number was significantly higher than that reported by previous studies in which the currency was examined under a microscope. Despite the discovery of such a high degree of contamination, the investigators could identify only approximately 20% of the non-human DNA they found because, to date, many microorganisms have not been cataloged in genetic data banks.

The most commonly found bacterium was the one that causes acne. Others were associated with gastric ulcers, pneumonia, food poisoning. Some carried genes responsible for antibiotic resistance. Bacteria identified were: Acinetobacter species (antibiotic-resistant infections); Staphylococcus aureus (kin infections); Bacillus cereus (food-borne illness); Escherischia coli (food poisoning); Helicobacter pylori (gastric ulcers); Corynebactrium diptheriae (diphtheria).

The researchers were able to identify such a large number of different bacteria because they used high-speed gene sequencing and computerized database analysis, which allowed them to recognize organisms by their DNA, rather than by isolating the cells in culture and studying them under a microscope. In the study, the investigators analyzed the DNA found on 80 $1 bills that they collected last year from an unnamed bank in Manhattan. Approximately 1.2 billion DNA segments were found on the bills. It required approximately 320 gigabytes of digital storage to hold all the genetic data; this was equivalent to the amount of storage space required to hold an entire library of traditional medical texts.

In addition to bacteria, the investigators found viruses, fungi and plant pathogens. They also found a very small amount of anthrax and diphtheria. They identified DNA from horses and dogs, and even two samples of white rhino DNA.

To improve the durability of paper money, nations such as Canada and the Kingdom of Bhutan are printing bank notes on sheets of flexible plastic polymer film; the researchers note that this affects the microbiology of money. A 2010 Australian study evaluated currency taken in change from supermarkets, coffee shops, and cafeterias in 10 nations. Bacteria levels varied widely from place to place; however, the researchers usually found fewer on polymer bills than on cotton-based ones. Other researchers attempted to grow bacteria on seven different currencies. They found that some bacteria survived longer on the plastic bank notes. The investigators note that handling money worsens the problem. Bacteria can feed on the waxy residue of skin and oils that accumulate on bills in circulation.

Studies have also examined the fibrous surface of paper money. Via traditional cell culture techniques, researchers in India, the Netherlands and the US have isolated approximately 93 species of bacteria adhering to paper bills. In 2012, microbiologists at Queen Mary University of London reported that approximately 6% of English bank notes tested had levels of E. coli bacteria comparable to the amount present on a toilet seat.

Take home message:

Many banks have hand sanitizers at their entrance. Also if you pay cash at he supermarket, use the hand sanitizers both before entering and while leaving the market. Also, carry a supply of hand sanitizers with you and wash your hands thoroughly or use a hand sanitizer any time you handle money. Don’t put your money where your mouth is.