Survival of Mycobacterium abscessus complex organisms on coins

To date, there have been no reports on the occurrence of nontuberculous mycobacterial (NTM) organisms (nor tuberculosis [TB]) on money, currency, banknotes, or coins, where these may act as fomites in the potential transmission of mycobacterial organisms around communities, especially in developing nations, where physical currency is still the popular mainstay of the economy, compared to electronic and digital forms of currency transaction. It was therefore the aim of this study to examine the survival of the Mycobacterium abscessus complex organisms on coins.

Coins from 17 countries were examined for the presence of M. abscessus complex organisms by broth enrichment in Middlebrook 7H9 for 2 months. Nickel-plated steel and copper-plated steel coins were artificially contaminated individually with M. abscessus complex (circa 10⁷ [7 log₁₀] organisms/coin), including M. abscessus subsp. massiliense (n = 2), M. abscessus subsp. bolletti (n = 2), and M. abscessus subsp. abscessus (n = 1) and their surviving cells enumerated at weekly period up to 5-week postinoculation.

NTM organisms were not isolated from coins from the 17 currencies examined. In all three subspecies of M. abscessus, the copper-plated steel coins caused a more rapid decline in organism numbers, which were statistically very significant (P < 0.0001), compared to the paired survival on the nickel-plated steel coins, whereby organisms were none detectable after 3-week storage on the copper-plated coins. NTM organisms survived better on the nickel-plated coins, with a mean count across all subspecies of log₁₀ 1.84 colony forming units per coin after 5 weeks of storage (range: 0.6-2.69 log₁₀ cfu/coin). There was no statistically significant difference (P > 0.05; 5%) in the survival dynamics among the three subspecies with storage on either coin type.

Health-care professionals should be aware of the survival of M. abscessus complex organisms on coins for up to 12 weeks, which may be particular relevant in high-risk areas of health-care institutions where TB or NTM is prevalent and where there are opportunities for the transmission of such organisms through contaminated fomites, including coins, through opportunities including payment for treatments/medicines/dressings, coin-operated payment facilities, such as hospital car parking, self-service vending machines, hospital canteens, coffee shops and dining halls and hospital shops, whether static or mobile onward visits. To mitigate potential infection consequences of handling coins contaminated with M. abscessus complex organisms, other NTMs organisms and TB, the authors support re-establishing the principles of basic hygiene, including proper handwashing and the avoidance of handling money when working with food or dressing wounds and skin lesions, as well as when working with respiratory devices, including nebulizers.