Bacterial diversity assessed by cultivation-based techniques shows predominance of Staphylococccus species on coins collected in Lisbon and Casablanca

Abstract

Money is usually considered a source of infections, yet survival of bacteria on dry metal surfaces is limited. The aim of this work was to assess the bacterial numbers and diversity on coins collected in Casablanca and Lisbon as these two cities, on different continents and only 585 km apart, have diverse cultural habitats, but have similar climate. A cultivation-based characterisation of the bacterial community showed that a relatively low number of cells per area of coin were found on both Moroccan Dirhams and Euros (0.014 and 0.125 colony-forming units (CFU) mm(-2) , respectively). Most of the bacterial isolates were located near the rim of the coins, and coins collected in Europe contained more CFU/area of coin. Coins collected in Europe and transported in pockets presented a higher number of bacterial isolates (maximum 0.125 CFU mm(-2) ) than coins transported in wallets (maximum 0.042 CFU mm(-2) ), regardless of the gender of the person transporting them, suggesting that temperature and moisture might be key parameters for bacterial survival on metallic coins. Bacterial diversity was higher for coins collected in Casablanca relative to coins collected in Lisbon, and there was no evidence that it was dependent on the gender of the person transporting the coins or the place of transport (pockets or wallets). Curiously, the percentage of Staphylococcus strains was 44% of the total isolates on both currencies.

Keywords: biodiversity; copper; fatty acid profile; metallic surface; money.