Profiling Bacillus cereus populations in a traditional style, hot-drinks vending machine and vended hot chocolate drink using polymerase chain reaction (PCR) and random amplified polymorphic DNA (RAPD) techniques

The vending industry in the UK is of significant size yet little work has been undertaken to identify and characterize the microbiological hazards present in vended products such as hot drinks. This work aimed to identify and characterize the microbial population within a hot-drinks vending machine and vended hot chocolate drinks. A hot drinks vending machine was operated using 2 brands of hot chocolate powder, from different manufacturers, for a period of one month. Samples from the mixing bowl, the dispense point, the vended drink and both vending powders were analyzed using polymerase chain reaction (PCR) and randomly amplified polymorphic DNA (RAPD) protocols. Of the 291 isolates examined, 90% were identified as Bacillus cereus using PCR. RAPD analysis indicated that the primary source of B. cereus in the vended drinks was the drinks powder, as 87% of the isolates from vended drinks shared an RAPD profile with isolates from the vending powders. The B. cereus found in the drink was also specific to the brand of powder used. However, some isolates were identified within the drinks that were found on the machine components but not the powders suggesting that the organism is able to persist within the machine and contaminate the vended drinks to a limited extent. Further characterization of the B. cereus isolated regarding potential for toxin production is required and may contribute to a quantitative microbiological risk assessment.