Microbial Screening

Ensure Patients Are Not Exposed to Unsafe Levels of Microorganisms

Microbial Contamination Screening

Microbial screening safeguards patient health. We conduct a detailed genomic screening for microbial species including human pathogens using qPCR and qPCR with Free DNA removal to determine live microbial contamination. We also use sophisticate plating methods to determine the quantity of colony-forming units per gram.

Microbes we test for include:

  • Pathogenic coliforms (EC)
  • Total Yeast & Mold (TYM)
  • Total Aerobic Bacteria (TAC)
  • Enterobacteriaceae (EB)
  • Aspergillus Flavus, Fumigatus, Niger and Terreus
  • Pathogenic Salmonella spp.
  • STEC E. coli

What Causes Microbial Contamination?

When we create ideal conditions for growing cannabis, we also create the best environment for bacteria and fungi, including yeast and molds, to thrive.

Contaminating microorganisms can be introduced from:

  • Contaminated tools, clothing, pots, etc.
  • Contaminated water
  • Manure-based fertilizers
  • Poor worker hygiene
  • Use of beneficial microbes

Microorganisms can propagate and be spread due to poor management of:

  • Crop rotation
  • Field sanitation
  • Irrigation
  • Moisture level
  • Planting density
  • Temperature

Ways to Prevent Contamination


Pick a Winner

Choose a cannabis strain that easily adapts to your growing environment. It is better to avoid delicate varieties to achieve diversity than to end up with unhealthy plants.

Air Circulation

Yeast and mold are responsible for most microbial testing failures of cannabis strains. Fungi typically grows in damp or humid areas, and in pools of water, and can be spread through spores in the air or by touch. Most growers find the best defense is to create and maintain clean air circulation, with HEPA or filtered HVAC systems, to keep mold spores below contamination causing thresholds.

During Growth

Easy Does It on the Nutrients

Dense vegetative growth from the overuse of nitrogen fertilizers creates soft plant tissue that is more susceptible to pest and fungal diseases.

Manage Humidity

Growing large amounts of cannabis indoors elevates humidity levels. While cannabis thrives in 80% to 100% humidity immediately after clone cutting, and in 65% to 70% humidity during the vegetative stage, humidity over 50% is dangerous to flowers during the bloom cycle.

Indoor humidity levels can be controlled using a dehumidifier or high powered exhaust fan controlled by a built-in humidistat or stand-alone atmospheric controller.

Don’t Overwater

Waterlogged soil can take days, if not an entire week, to dry. Drenched soil drowns the root zone, depleting it of oxygen.


While plants can amass ample problem-causing microbial elements, most problems arise post-harvest; after the plant is cut, during trimming, drying, and packaging.


Cutting, trimming, and harvesting create wounds that compromises the plant’s immune system and opportunities for molds and yeasts to take hold and spread. Finely chopped stems and leaves, or plant trim, is particularly susceptible to mold when it is moist, so growers would be wise to physically isolate cuttings from budding flowers.

Drying / Curing

Growers can trim the leaves and stems from the plant after it is hung and dried so wounds are not created while the plant is wet. Drying flowers faster can also lower the risk of mold, but at a cost to the product’s flavor.


Above all, take extra care when handling plants. Fingers, clippers, and packaging can all expose plants to yeast and mold. Development and adherence to excellent sanitary practices can help ensure your buds pass our rigorous safety tests.

What Causes Microbial Contamination?

Cannabis is an extremely hardy plant partly because of its natural ability to fend off microbial invasions. As with humans, its innate immune system can be compromised by stress, disease, invaders, and open wounds or cuts. Keeping plants healthy during the growing and flowering cycles and curing plants properly after harvest minimizes microbes in the plant material.