Investigation into the Prevalence, Persistence and Antibiotic Resistance Profiles of Staphylococci Isolated from Euro Currency

Aims: The study set out to sample €10 banknotes for the presence of coagulase-positive staphylococci (CPS) such as Staphylococcus aureus (S. aureus) and coagulase-negative staphylococci (CoNS) in Southern Ireland, to assess the levels of antibiotic resistance among those isolated, and determine the persistence of S. aureus on €10 banknotes and €2 coins.

Methods and Results: We report that 97% of €10 banknotes screened (n = 155) harboured multiple species of staphylococci. From the generated bank of strains, a total of 150 representative staphylococci isolates were used for further study, 71 were CPS and 79 were CoNS. Of these, we found that 62% of the staphylococci demonstrated resistance to at least one of the first-line antibiotics (52_11% of CPS isolates and 76_71% of the CoNS isolates). Resistance to multiple antibiotics was seen in 31_18% of the resistant isolates. In relation to persistence studies, S. aureus was shown to remain viable on euro banknotes and coins for significant periods (on average, 19_33 days on €10 banknotes and 16_67 days on €2 coins) as determined using bioluminescence.

Conclusions: We advocate the expansion of antibiotic surveillance programs, with a view to tracking/monitoring antibiotic resistance dissemination among environmental contaminants. Additionally, we propose that ‘cashless transactions’ should be encouraged in high-risk environments such as hospitals and healthcare settings, as well as stricter infection controls.

Significance and Impact of the Study: Although it is accepted that circulating currency has the potential to harbour disease-causing pathogens, studies investigating prevalence and persistence of such pathogens on euro currency are virtually nonexistent. In an attempt to rectify this, we examined the prevalence of staphylococci on €10 banknotes in Ireland and reported relatively high levels of antibiotic resistance among the isolates. Furthermore, we have established the persistence of S. aureus on euro currency for the first time.