Dirty Money: A Matter of Bacterial Survival, Adherence, and Toxicity

Abstract

In this study we report the underlying reasons to why bacteria are present on banknotes and coins. Despite the use of credit cards, mobile phone apps, near-field-communication systems, and cryptocurrencies such as bitcoins which are replacing the use of hard currencies, cash exchanges still make up a significant means of exchange for a wide range of purchases. The literature is awash with data that highlights that both coins and banknotes are frequently identified as fomites for a wide range of microorganisms. However, most of these publications fail to provide any insight into the extent to which bacteria adhere and persist on money. We treated the various currencies used in this study as microcosms, and the bacterial loading from human hands as the corresponding microbiome. We show that the substrate from which banknotes are produced have a significant influence on both the survival and adherence of bacteria to banknotes. Smooth, polymer surfaces provide a poor means of adherence and survival, while coarser and more fibrous surfaces provide strong bacterial adherence and an environment to survive on. Coins were found to be strongly inhibitory to bacteria with a relatively rapid decline in survival on almost all coin surfaces tested. The inhibitory influence of coins was demonstrated through the use of antimicrobial disks made from coins. Despite the toxic effects of coins on many bacteria, bacteria do have the ability to adapt to the presence of coins in their environment which goes some way to explain the persistent presence of low levels of bacteria on coins in circulation.

Should we leave the paper currency? A microbiological examination

“…Humid conditions improved persistence for most types of bacteria, such as Salmonella typhimurium, P. aeruginosa, E. coli or other relevant pathogens [2,9,21,25]. In previous studies, reported that Enterobacteraceae members are 13%-55.5% range of the paper currencies and the most frequently isolated enteric bacteria was E. coli (19.4-48.14%) [2,3,9]. Antimicrobial resistance is a global phenomenon that has resulted in high morbidity and mortality as a result of treatment failures and increased health care costs.…”

“…can survive on inanimate surfaces even for months. Overall, Gram-negative bacteria have been described to persist longer than Gram-positive bacteria [3,21]. Humid conditions improved persistence for most types of bacteria, such as Salmonella typhimurium, P. aeruginosa, E. coli or other relevant pathogens [2,9,21,25].…”

“…Antimicrobial resistance is a global phenomenon that has resulted in high morbidity and mortality as a result of treatment failures and increased health care costs. Research has shown that contaminated fomites in general and paper currency in particular, plays a key role in the spread of bacterial infections with antimicrobial resistance [2,3,25]. Heshiki et al [22] in a metagenomic study showed that the antimicrobial resistance genes on banknotes were significantly higher (4.86 times more) than environmental samples such as water, air, soil and dust.…”

“…As a result, paper money is contaminated with microorganisms from the human hand, mouth and even in the gastrointestinal tract microbiota. As a result of the exchange of these contaminated banknotes among people, microorganisms begin to spread, contributing to the spread of both antibiotic resistance and many virulence factors and they pose a risk to public health [2,3]. Researches show that the most common microorganisms carried with paper money were enteric bacteria such as Salmonella spp., Shigella spp., Klebsiella spp.…”

Filthy lucre: A metagenomic pilot study of microbes found on circulating currency in New York City

“…In vitro culture studies have established that paper currency can harbor high levels of microbes, some of which are clinically significant, such as the causative agents of pneumonia and enteric diseases [18–20], and various antibiotic resistant strains [21]. Laboratory simulations also provide evidence that many microorganisms can survive on office paper [22], coins [23] and banknotes of various materials [19, 24]. These studies, though limited, have established that microbial contamination of paper currency is widespread, and that money represents an important human-microbe interface.…”