4:54 PM
antimicrobial
A St. Petersburg College biological sciences professor and some of her students set out to discover how much, if any, “bad bacteria” is found on frequently handled fomites like paper money and credit cards. The preliminary findings from the study titled, “"Cash or Credit: Spreading the Wealth of Virulence Genes?", were released Monday.
Shannon McQuaig, Ph.D., Associate Professor, Department of Natural Sciences at St. Petersburg College spoke to the Infectious Disease Examiner Monday about the study and their preliminary findings.
Dr. McQuaig and her students tested paper money and plastic currency for this “bad bacteria” using molecular techniques looking for various antibiotic resistance and virulence-associated genes.
What they found was the high prevalence of methicillin resistant Staphylococcus aureus(MRSA) on both the paper money and the plastic credit cards.
McQuaig said of the “non-hospital” (malls, fast food restaurants, gas stations, etc.) dollar bills tested, approximately 80 percent of the cash tested had MRSA on it. This compared to just 20 percent of the “hospital” cash (health care workers for example).
When asked about whether she was surprised by this finding, because the health care setting are a well-known source for MRSA, Dr. McQuaig responded, “Initially, I expected hospital-associated dollar bills would harbor the highest percentage of MRSA; however, after observing the lower percentage I did a little research into the matter and found a few things that may be contributing to the lower percentage.
“First, hospitals have advertised hand-washing/hand-sanitizing practices with flyers in bathrooms and on walls throughout the lobby, which increases awareness. Second, hospital bathrooms tend to use soap containing triclosan, while some organisms have developed resistance to triclosan; however, MRSA is still sensitive to this antimicrobial chemical. Third, according to the CDC hospital-associated MRSA infections have actually been decreasing over the past few years while community-acquired MRSA infections have been increasing.”
In addition, McQuaig and her students reported that 50 percent of the credit cards tested also tested positive for MRSA.
Being a higher percentage than expected, Dr. McQuaig told Examiner.com that credit cards are less porous and many sources have suggested the switch to plastic currency because of decreased contamination.
“I believe there has been a general trend to use plastic currency more frequently, as a simple convenience (I hardly ever carry cash), but as it is used more frequently it is exposed to more hands and thus possibly more contamination.
“Although, on average, credit cards are still not handled as much as dollar bills. Volunteers in this study estimated using them from once per month to 10-20 times per week”, she notes.
The study was paid for by a grant from The Foundation at St. Petersburg College. The goal of the Foundation is to provide student enrichment and faculty professional development.
Dr. McQuaig says once the study is complete, they plan to publish the data in a peer reviewed journal.
Staphylococcus aureus is a bacterium found colonizing (without causing infection) the skin and nose in one quarter to one third of people.
Methicillin –resistant Staphylococcus aureus (MRSA) is a highly resistant type, in which beta-lactam antibiotics (penicillins and cephalosporins) are ineffective in treatment.
What was once restricted to hospital infections, MRSA is becoming increasingly common in community acquired infections.
MRSA is primarily spread person to person via close skin contact, through cuts and abrasions and poor hygiene.
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