Transcript Bednar - York College of Pennsylvania

Are Microorganisms Present on Commonly used Coin
Currency?
Laura Bednar Department of Biological Sciences York College of Pennsylvania
Introduction
Purpose
•To determine if microbes are present on
quarters, dimes, nickels and pennies.
•To identify classes of organisms on each
contaminated coin.
•To test null hypothesis that there is no difference
between 0/10 and the coin samples.
Material and Methods
Collection of Samples
•40 petri dishes (10 each
coin) used to collect samples
•Sterile forceps used to hold
coin
•Cotton swab was dipped in
nutrient broth and then
swabbed covering entire area
of coin
•Cotton swab placed back
into broth and incubated
Results
There were 16 coins that had contamination
on the 40 coin samples. Using a measure of
proportions using the z-statistic (Triola 2001)
it was found that quarters and pennies were
found to have a significance level of .02
suggesting there is no difference between
null hypothesis and coin contamination.
Dimes were found to be significant at the .01
level. Nickels were highly significant at the
.001 level. Dimes and nickels reject null
hypothesis.
Streak Plating
•A loopful of broth was taken
and a streak plate was made
Proportion Contaminated with Microbes
**
0.6
Proportion N=10
0.5
*
0.4
0.3
0.2
0.1
Observations
0.0
Quarter
Dimes
Nickels
Pennies
Types of Coins
•Based on cell shape, size, and
color; if plate had growth a smear
was made
* Significant
** Highly Significant
Quarter
Dime
Nickel
Penny
4
Gram Staining
•Once smear was made Gram
stain was done following Standard
procedure
3
2
1
0
Gram + cocci Gram+ Rod Gram- Rod
Types of Microbes Found
The proportion of coins that had microbes present
varied among the four coins. Nickels had the most
coins with contamination present on 6 of the 10.
The four types of classes of organisms found were
G+ cocci, G+ rod, G-rod and Yeast. Most of the
organisms found were Gram positive cocci and
Yeasts. These two organisms are common skin
resident and transient organisms. The Gram positive
cocci organisms are probably some species of
Staphylococcus based on their cluster formation seen
in the Gram stain. These organisms have been
known to cause infections in susceptible people
(Solberg 2000).
A difference in each coin’s ability to provide host for
bacteria depend upon the metals each contains.
Quarters and dimes are made of the same material.
Because of the size difference it was expected that
quarters would have greater contamination, however
the inhibiting effects were greater in quarters leading
to less contamination. Metals such as zinc have
been shown to inhibit growth of bacterial organisms in
past research (Andrade 2004, Makarov 2004). All
coins except for nickel have zinc in them. This may
be why nickel has the greatest contamination.
Conclusions- Each type of coin did contain microbes
and nickels had the most contamination. The four
types of microbes found were G+ cocci, G+rod, Grod, and Yeast.
Literature Cited
Types of Microbial Organisms on Coins
Number of colonies
It was observed by many employees at a local
supermarket that their hands were commonly dirty
after handling money. A question arose in that is the
money really dirty and contaminated with bacteria.
While other research has been done on other fomites
transferring bacteria to other surfaces, little research
has been done in investigating the microbiology of
money. The use of money to pass pathogenic
bacteria could be a way for bacteria to infect the
general population. One study done on dollar bills
showed that 94% of dollar bills were contaminated
with bacteria (Pope, et. al. 2002).
No current research can be found on the microbiology
of coins. American coins are made of three basic
metals. Those metals are copper, zinc and nickel.
Metal has been shown to inhibit bacterial growth in
solution (Andrade et. al. 2004, Makarov et. al. 2004).
Quarters and Dimes have the same inner core of zinc
and the same outer layer composed of 75 copper 25
nickel alloy, but are different sizes. Nickels are made
entirely of the outer core alloy that quarters and dimes
are made of. Pennies are made of zinc plated copper.
These varying compositions of metal may affect the
amount of bacteria present. The presence of metal
around bacterial cells can be a toxic situation for the
organisms. This research examines if microbes are
found contaminating coins, what common subgroups
of organisms are found, and if there is a significant
difference between the four coins. Based on
observations and past research, the coins will contain
microbial organisms and there will be a difference
between the number of coins contaminated.
Discussion
Andrade LR, et. al. Effects of copper on Enteromorpha flexuosa
(Chlorophyta) in vitro. Ecotoxicology Environmental Safety. May 2004 117-125.
Makarov AA, et. al. Zinc (II)-mediated inhibition of ribonuclease Sa by an Nhydroxyurea nucleotide and its basis. Biochem Biophys Resource
Communication. June 2004 152-156.
Pope, Theodore W. et. al. Bacterial Contamination of Paper Currency.
Southern Medical Journal. December 2002 1408-1411.
Solburg, Claus. Spread of Staphylococcus aureus in Hospitals: Causes and
Prevention. Scandinavian Journal of Infectious Diseases. March 2000 587595.
Triola, Mario F. Measure of proportions using the Z-statistic. Elementary
Statisitic 8th edition. 2001 409-412.
Yeast
Acknowledgements
•Dr. Mathur, Mentor
•Mrs. Taylor