Bacterial contamination of paper currency.

ABSTRACT: One-dollar bills were collected from the general community in western Ohio to survey for bacterial contamination. Pathogenic or potentially pathogenic organisms were isolated from 94% of the bills. These results suggest a high rate of bacterial contamination of one-dollar bills.

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ENTERING the antibiotic era, it was anticipated that morbidity and mortality from infectious diseases would continue to decrease over time. However, the death rate from infectious diseases increased by 58% from 1980 to 1992, making it the third leading cause of death by 1992. (1) There is also significant morbidity from infectious disease. Furthermore, with the emergence of drug-resistant pathogens, many infections have become more difficult to treat. Since communicable diseases can spread through contact with fomites, paper currency could play a role.

Paper currency is widely exchanged for goods and services in this country and in most countries worldwide. In 1999, the United States Department of the Treasury printed more than 35 billion one-dollar bills, each with a lifespan of about 18 months. (2) One-dollar bills are widely used, and each bill is exchanged many times during the time it circulates. If some of these bills are contaminated with pathogenic bacteria, there is potential to spread these organisms.

Data regarding the bacteriologic contamination of paper currency are limited. A review of the medical literature revealed only one investigation involving the bacterial contamination of money in the United States. (3) Our study adds to this limited body of literature.

MATERIALS AND METHODS

We solicited one-dollar bills from the general public at two sites: the checkout line at a local grocery store and the line to a concession stand at a local high school during a basketball game. Volunteers were eligible to participate if they had a one-dollar bill in their possession. All eligible persons who were approached agreed to participate. Demographic data regarding the volunteers were not collected. Those who agreed to participate were instructed to roll the bill and place it directly into a vial of brain-heart infusion broth. They were then reimbursed with new one-dollar bills. After soaking for 30 to 60 minutes, the bill was removed with sterile tweezers and the broth was allowed to incubate at 37[degrees]C for another 12 to 24 hours. Using a standard 10 [micro]L loop, the broth was then streaked onto blood and chocolate agar, incubated at 37[degrees] C, and monitored for growth of bacterial colonies.

Bacterial colonies were identified using standard microbiologic techniques. When necessary, these techniques were augmented with the VITEK and API-20E (boiMerieux Inc, Hazelwood, Mo) automated identification systems. When plates were heavily overgrown with common skin contaminants such as [alpha]hemolytic Streptococcus and coagulase-negative Staphylococcus, further identification was not accomplished.

RESULTS

The 68 one-dollar bills collected yielded 93 bacterial isolates. Bacterial colonies were isolated from 64 bills (94%). Five bills (7%) yielded bacteria considered pathogenic to healthy hosts and 59 bills (87%) yielded bacteria considered potentially pathogenic to hospitalized or immunocompromised hosts. Four bills (6%) had no significant growth. An overview of the results is given in the Table.

Of the 5 bills yielding pathogenic bacteria, 2 showed Staphylococcus aureus and 3 showed Kielisiella pneumoniae. The remaining isolates consisted of coagulase-negative Staphylococcus, [alpha]-hemolytic Streptococcus, Enterobacter species, Acinetobacter species, non-aeruginosa species of Pseudomonas, Bacillus species, Alcaligenes species, diphtheroids, and Escherichia vulneris. There was no significant growth from 4 of the one-dollar bills.

DISCUSSION

Bacteria have been shown to be spread from person to person via contact with fomites. Paper currency is commonly and routinely passed among individuals. Thus, bacteria could be spread on the surface of paper currency. This study suggests that bacterial contamination of paper currency nearly universally occurs. While this study was not designed to document transmission of bacteria from person to person during the exchange of money, one would expect this might occur.

In the early 1970s, Abrams and Waterman (3) reported potential pathogens on 13% of coins and 42% of paper currency collected from laboratory personnel. They isolated coagulase positive Staphylococcus, Escherichia coli, Klebsiella sp, Pseudomonas aeruginosa, and Proteus mirabilis. They did not consider coagulase-negative Staphylococcus a potential pathogen.

The money collected in the current study was also commonly contaminated. Among the more virulent of organisms isolated was Staphylococcus aureus, a hardy non--spore-forming organism that can survive for prolonged periods outside of a living host. Klebsiella pneumoniae is a virulent organism that may cause both community and hospital acquired infections.

Most of the remaining isolates identified in this study do not commonly cause disease in the nonhospitalized host. However, in hospitalized or immunocompromised patients, these bacteria can cause clinically significant infections. Natural inhabitants of human skin such as coagulase-negative Staphylococcus were formerly considered nonpathogenic. It is now known that these bacteria do cause clinically significant disease. Infection with coagulase-negative Staphylococcus is typically associated with indwelling foreign bodies. These infections are usually indolent, but resistance to antibiotics can make them difficult to treat.

The Enterobacter species, Acinetobacter species, and non-aeruginosa species of Pseudomonas are ubiquitous environmental organisms. These bacteria rarely cause primary human disease in healthy hosts but have been reported to cause serious nosocomial infections or infections in immunocompromised hosts. (4-6) Bacillus species, Alcaligenes species, diphtheroids, and Escherichia vulneris have been reported to cause clinically significant infection in individuals with specific risk factors such as indwelling catheters. (7-10)

The limitations of this study should be recognized. These 68 one-dollar bills are only a small sample of the billions of bills in the general circulation. A much larger study would be required to report with certainty the percentage of bills contaminated with pathogenic bacteria. However, this study does show that contamination of paper currency with potentially harmful bacteria occurs.

Although the clinical significance of bacterial contamination of paper currency is unknown, transmission of resistant organisms from person to person could be significant even if the recipient is initially only colonized. These organisms may later cause a clinically significant infection if the individual is hospitalized or becomes immunocompromised.

This study was not designed to prove transmission from person to person via paper currency. A more complex study using molecular methods would be required to accomplish that objective. However, these results do suggest that paper currency is commonly contaminated with bacteria. This contamination may play a role in the transmission of antibiotic resistant or potentially harmful organisms.

TABLE

Organisms Isolated From 68 One- Dollar Bills.

                                      No. of
                                     Isolates

Total isolates                   93
Common pathogens
  Klebsiella pneumoniae                    3
  Slaphylococcus aureus                    9
  Total Common Pathogens          5
Potential pathogens
  Mixed gram-positive cocci *             54
  Enterobacter species                    14
  Acinetobacter species                    8
  Pseudomonas pulida                       3
  Bacillus species                         5
  Alcaligenes species                      2
  Diphtheroids                             1
  Escherichia vulneris                     1
Total potential pathogens        88

* Primarily coagulase-negative Staphylococcus and [alpha]- hemolytic
Streptococcus.

References

(1.) Pinner RW, Teutsch SM, Simonsen L, et al: Trends in infectious diseases mortality in the United States. JAMA 1996; 275:189-193

(2.) United States Treasury, Bureau of Engraving and Printing. Facts and trivia. Available at: http://www.bep.treas.gov. Accessed December 18, 2000

(3.) Abrams BL, Waterman NC: Dirty money. JAMA 1972; 219:1202-1203

(4.) National Nosocomial Infections Surveillance (NNIS) Report: Data summary from October 1986-April 1996, issued May 1996. Am J Infect Control 1996; 24:380-388

(5.) Glew RH, Moellering RC Jr, Kunz LJ: Infections with Acinetobacter calcoaceticus (Herellea vaginicola): clinical and laboratory studies. Medicine (Baltimore) 1977; 56:79-97

(6.) Gilligan PH: Pseudomonas and Burkholderia. Manual of Clinical Microbiology. Murray PR, Baron EJ, Pfaller MA, et al (eds). Washington, DC, American Society for Microbiology, 6th Ed, 1995, pp 509-519

(7.) Silman R, Rehm S, Shiaes DM: Serious infections caused by Bacillus species. Medicine 1987; 66:218-223

(8.) Duggan JM, Goldstein SJ, Chenoweth CE, et al: Achromobacter xylosoxidans bacteremia: report of four cases and review of literature. Clin Infect Dis 1996; 23:569-576

(9.) Coyle MB, Lipsky BA: Coryneform bacteria in infectious diseases: clinical and laboratory aspects. Clin Microbiol Rev 1990; 3:227-246

(10.) Spaulding AC, Rothman AL: Esdzerichia vulneris as a cause of intravenous catheter-related bacteremia. Clin Infect Dis 1996; 22:728-729

KEY POINTS

* Paper currency has a high rate of bacterial contamination.

* Both pathogenic or potentially pathogenic organisms were isolated from paper currency.

* While paper currency may be highly contaminated with bacteria, it is not known what role this plays in the transmission of disease.

From the Department of Internal Medicine, Division of Infectious Diseases, and the Department of Pathology, wright-Patterson Medical center, wright-Patterson AFB, Ohio.

The views expressed in this article are those of the authors and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the United States Government. This study was funded by the United States Department of Defense.

Reprint requests to col Thomas M. Koroscil, USAF, MC, Department of Internal Medicine, 74 MDOS/SGOMI, 4881 Sugar Maple Drive, wright-Patterson AFB, OH 45433-5529.