Currency Notes
Paper currency is commonly and routinely passed among individuals, and microbes can be spread on the surface of paper currency (Figure 1). Paper currency is made of a rugged mix of 75% cotton and 25% linen, and offers surface area for bacteria and microorganisms to reside on both sides.[10] Polymer-based banknotes presented lower bacterial counts than cotton-based banknotes.[11] It is possible that the fibrous surfaces of cotton-based banknotes provide a good surface for bacterial attachment.[11] As a result, fewer bacteria were isolated in Australia and New Zealand, where polymer-based banknotes were tested.[11] Moreover, in banknotes from Mexico, where both polymer and cotton-based notes are used, it was found that polymer-based banknotes were much less contaminated than cotton-based notes.[11] The longer the paper bill remains in circulation, the more opportunity there is for it to become contaminated, and lower-denomination notes receive the most handling because they are exchanged more often.[10,11] In addition, the economic status of a country was associated with the concentration of bacteria on the currency, and it was found that the average number of bacteria detected on banknotes is associated with the economic freedom of banknotes.[11]
Figure 1.
Most common pathogens detected in banknotes and coins.
Bacteria
The amount of bacterial contamination on currency varies widely between countries (Figure 2). As a result, 88% of the paper notes tested in Jeddah, Saudi Arabia were contaminated with a variety of microorganisms,[12] and 94% of US$1 bills had bacterial contamination.[13] Approximately 80% of the paper notes tested in Bangladesh and 89% of the paper notes tested in Nigeria had bacterial contamination, whereas in Ghana, 100% of the currency notes tested were found to be contaminated with one or more bacterial species.[14] However, no difference was found in the bacterial presence among cotton-based notes from Nigeria, The Netherlands and Mexico.[11] In addition, more bacterial contamination existed on older Egyptian[10] and Saudi Arabian paper notes than on new ones.[12] The number of bacteria per square cm on banknotes was also different between countries. As a result, polymer-based banknotes from Australia and New Zealand presented less than 10/cm2 bacteria, whereas cotton-based notes from China presented more than 100/cm2 bacteria.[11] Cotton-based notes from the USA contained about 10/cm2 bacteria.[11] By contrast, on currency from Rangoon, Myanmar, total bacteria and fecal coliform counts were much higher, ranging from 0–2.9 × 107/cm2.[15] The number of bacteria on currency also varies within a single country, as the number of bacteria isolated from US currency varied from 20 to 2.5 × 104 CFU[11] In Nigeria, currency notes had also a high level of contamination, reaching 4 × 105 CFU.[16] Various bacteria have been isolated from money worldwide, including developed countries, and microbes, such as S. aureus, E. coli, Klebsiella spp. and Enterobacter spp., have been identified as common contaminants (Table 1). In the 1970s, Abrams and Waterman found that the 42% of paper currency collected from laboratory personnel was contaminated by potential pathogens, such as S. aureus, E. coli, Klebsiella sp., P. aeruginosa and Proteus mirabilis.[6] Similarly, US$1 bills and Egyptian paper money yielded pathogenic agents, such as S. aureus and Klebsiella pneumonia, or other bacterial contaminants, such as coagulase-negative staphylococci, α-hemolytic streptococci and Acinetobacter sp..[10,13] In India, approximately 18–69 CFU of S. aureus were isolated per banknote.[17] Moreover, many bacterial agents have been isolated from banknotes in studies from India, Bangladesh, Saudi Arabia, Turkey, Nigeria, Kenya, Pakistan, Myanmar, Egypt and Nepal (Table 1).[15,16,18–27] In addition, Vibrio cholera were isolated from paper money samples obtained from Bangladesh;[21]Vibrio sp. have also been detected in Rangoon, Myanmar[15] and India.[18] In a recent study on banknotes from different countries, it was found that E. coli was most commonly isolated on banknotes from the USA and China, and a Salmonella sp. was isolated only from samples in the USA, China and Ireland, while the presence of S. aureus varied.[11] Moreover, bacterial isolates from currency exhibited a high incidence of antibiotic resistance.[11] In summary, several bacteria species have been isolated from banknotes from different countries.
Figure 2.
Infectious agents isolated from paper currency from different countries.
Other Agents
In a study performed in the 1970s, various yeast and fungi were isolated from paper currency collected from laboratory personnel.[6] In addition, 118 saprophytic fungal isolates were isolated from currency notes in India.[19] More recently, fungi were isolated from both old and new currency notes in Riyadh, Saudi Arabia.[26] The most commonly isolated fungal species was Aspergillus niger, followed by Aspergillus flavus, Candida spp., Penicillium spp. and Rhizopus spp..[26] In another study in India, currency notes from different occupational groups were evaluated for the presence of microbial contaminants, and fungi such as Aspergillus niger and Fusarium spp. were isolated from these currency notes, in addition to common pathogenic bacteria.[30]
Currency notes contaminated with parasites were found in a study performed in Nigeria.[29] Notes were found to be contaminated with Ascaris lumbricoides (8%), Enterobius vermicularis (7%), Trichuris trichiura (3%) and Taenia spp. (4%).[29] Moreover, parasitic contamination was most prevalent on dirty/mutilated notes collected from butchers, farmers and beggars.[29]
Future Microbiol. 2014;9(2):249-261. © 2014 Future Medicine Ltd.
