Microbial contamination on currency notes: a comparative study of denominational variability

Background: Currency notes are among the most commonly exchanged items in daily life and can act as potential carriers of pathogenic microorganisms. This study aimed to assess the microbial contamination present on Indian currency notes of different denominations ( JOURNAL/rrmm/04.03/02272794-990000000-00137/inline-graphic1/v/2025-11-21T113423Z/r/image-jpeg 10, JOURNAL/rrmm/04.03/02272794-990000000-00137/inline-graphic2/v/2025-11-21T113423Z/r/image-jpeg 20, JOURNAL/rrmm/04.03/02272794-990000000-00137/inline-graphic3/v/2025-11-21T113423Z/r/image-jpeg 50, and JOURNAL/rrmm/04.03/02272794-990000000-00137/inline-graphic4/v/2025-11-21T113423Z/r/image-jpeg 100). Materials and methods: A total of 32 Indian currency notes were selected for microbiological analysis, comprising eight notes each from JOURNAL/rrmm/04.03/02272794-990000000-00137/inline-graphic5/v/2025-11-21T113423Z/r/image-jpeg 10, JOURNAL/rrmm/04.03/02272794-990000000-00137/inline-graphic6/v/2025-11-21T113423Z/r/image-jpeg 20, JOURNAL/rrmm/04.03/02272794-990000000-00137/inline-graphic7/v/2025-11-21T113423Z/r/image-jpeg 50, and JOURNAL/rrmm/04.03/02272794-990000000-00137/inline-graphic8/v/2025-11-21T113423Z/r/image-jpeg 100 denominations. These samples were then carefully sealed in sterile packets and immediately transported to the laboratory for further processing. All currency notes were analysed for the presence of bacterial pathogens, including Staphylococcus aureus , Pseudomonas spp. , Klebsiella spp. , and Escherichia coli . Results: Escherichia coli exhibited the highest and S. aureus shows lowest microbial growth, respectively. Tukey's Honestly significant difference (HSD) post hoc analysis revealed significant variations in microbial load across denominations, with E. coli exhibiting the highest contamination levels on JOURNAL/rrmm/04.03/02272794-990000000-00137/inline-graphic9/v/2025-11-21T113423Z/r/image-jpeg 100 notes. Conclusion: The findings highlight that currency notes harbour more pathogens, emphasizing the role of physical note quality and handling in microbial transmission. Therefore, it is important to raise public awareness about hygiene practices and recommend the use of digital currency over paper currency.