We’ve talked before about keeping your coffeemaker clean. There was a new study that tested Nespresso machines and monitored the colonization of bacteria from 10 different machines. Among the bacteria found were enterobacteria other coffee-adapted bacteria. They sampled what they are calling coffee leach waste that formed on the drip trays of the coffee makers to see what colonies grew on them.
The most frequent bacteria found were Pseudomonas sp. Also found was Enterococcus spp.
Chronological series of SEM images of the drip tray samples taken after 4 (A), 8 (B), 14 (C), and 21 days (D) of operation. Figure C corresponds to a sample highly abundant in Bacillus spp. Scale bars are indicated in each case.
Vilanova, C. et al. The coffee-machine bacteriome: biodiversity and colonisation of the wasted coffee tray leach. Sci. Rep. 5, 17163; doi: 10.1038/srep17163 (2015).