Microbiological spoilage is the deterioration of a product due to activity by microorganisms such as bacteria, yeast and moulds making the product undesirable or unsafe for consumption.

Cannabis crops may be exposed to microbiological contamination from irrigation water, growth mediums or through human activity during the cultivation process. Facilities growing medicinal cannabis control these parameters to minimise micro-organisms in the crop. Microbial contamination often occurs post-harvest, during long term storage and handling as well. The presence of bacteria such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), amongst others, is detrimental to humans, particularly in vulnerable persons such as children, the elderly and those with compromised immune systems.