Bacterial Contamination of Circulating Yemeni Banknotes in Sana’a City: Evidence from a Cross-Sectional Study

Abstract

Background: Since people handle paper money a lot, it could be a way for microorganisms to spread.  There is little information about how microbes get onto circulating banknotes in Yemen, even though cash is widely used there.

Objective: To characterize bacterial contamination of Yemeni banknotes circulating in Sana’a City, describe organism profiles, and examine the distribution of contaminated notes by denomination.

Methods: In a cross-sectional survey, 116 banknotes of different denominations were gathered through convenience sampling from six exchange points (university cafeterias, grocery stores, pharmacies, qat markets, mechanic workshops, and currency-exchange shops) in Sana’a City. Saline-moistened sterile swabs were used to clean both sides of each note. We did cultures on blood agar, MacConkey agar, and TCBS agar and kept them at 37 °C (24–48 h) in an aerobic environment. Colony morphology, Gram stain, and standard biochemical tests were used to identify the organism.

Results:  Bacterial growth was obtained from all banknotes. Gram-positive organisms comprised 84/116 (72.4%) and Gram-negative 32/116 (27.6%). Predominant taxa were Corynebacterium spp. (diphtheroids) 41/116 (35.3%), Staphylococcus aureus 33/116 (28.5%), and Enterobacter spp. 18/116 (15.5%); less frequent isolates included Staphylococcus epidermidis, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Shigella spp., and Serratia marcescens. The Gram-category distribution differed from a 50:50 expectation (χ²=23.31, df=1, p<0.001). Contaminated notes were unevenly distributed by denomination (250: 26.7%; 50: 17.2%; 100: 17.2%; 500: 16.4%; 1000: 13.8%; 200: 8.6%); goodness-of-fit was significant (χ²=12.17, df=5, p=0.033).

Conclusion: Circulating banknotes in Sana’a City are consistently contaminated, with a significant predominance of Gram-positive organisms and a disproportionate burden among lower denominations. Practical risk-reduction measures, especially hand hygiene after cash handling.