Automatic Vending-Machines Contamination: A Pilot Study

Hot-drinks vending machines are disseminated worldwide and millions of drinks are served every day. Because of a small number of studies on hot-drinks related illnesses, the aim of this pilot study was to identify the presence and load of bacterial species, potentially harmful for consumers, within hot-drinks vending machines external critical surfaces. This preliminary cross sectional study was carried out in April 2015 at the University of Siena, Italy. Samples were taken from the critical surfaces of 4 hot-drinks vending machines (VM); the analyzed VM’s critical surfaces were: Dispense Areas, Nozzles and Glass-Holders. The samples were sown on selective culture media: Plate Count Agar (PCA) at 22°C and 36°C, Slanetz and Bartely Agar (SBA) and Mannitol Salt Agar (MSA). Total Viable Count (TVC) at 36°C and 22°C was assessed for mesophilic and psychrophilic contamination. Results were expressed in terms of average CFU/cm2. Descriptive and statistical analyses were performed in order to assess which surface was the most contaminated. The nozzles resulted to be the most contaminated critical surface, showing average values over the limits in all the culture media (PCA 36°C, PCA 22°C, MSA and SBA). The statistical analysis showed that the nozzles were significantly more contaminated (p <0.05) than Dispense Areas and Glass-holders both in PCA 36°C and in PCA 22°C. Given the high number of CFU/cm2, VM may constitute a potential threat for consumer’s health, reason for which further studies are recommendable.