Microbiology Testing: Why? And What to Test For.

In this post:

  • Mold and mildew risks & prevention
  • E.coli / coliforms risks & prevention
  • Aerobic bacteria risks & prevention
  • Enterobacteriaceae risks & prevention
  • ACS testing methods
  • Microbiology compliance

Mildew, E.coli, Aerobic Bacteria and  Enterobacteriaceae are common microbiological contaminants that can destroy your harvest and pose serious health risks to consumers. But measures can be taken to protect your plants from contamination and to guarantee that your final product is safe for use.

At ACS Laboratory we work with hemp, CBD, and cannabis companies to test for common contamination of microorganisms and bacteria that can be dangerous to customers and your brand’s reputation. We use award winning protocols to conduct testing on cannabis flower, edibles and extracts, so you can feel confident about the quality of your product.  

Mold and Mildew

What are They?

Mold and mildew are types of fungi that grow rapidly in moist warm areas on almost any type of surface. Powdery mildew (white mold) is a common fungal disease that appears like a whitish residue on leaves.

It often starts on the undersides of leaves and can also spread to stems, flowers, and buds. If you don’t notice it right away, white mold can spread quickly. Another common strain is grey mold (botrytis), which is much more invasive

The Health Risks

If you don’t catch mold and mildew right away, it can spread like wildfire to leaves and buds, making them completely unusable. Later on, if your finished product develops mold, your customers may be exposed to unsafe levels. Direct inhalation of mold spores can lead to respiratory illnesses, especially in people with compromised immune systems.

How to Prevent It

Unfortunately, mold can be difficult to spot before it spreads. That means it’s vital to monitor your plant throughout its lifecycle and test it immediately after harvest. If your plant is grown indoors, you have more flexibility to control the temperature and air exposure.

Make sure to monitor your plants for proper ventilation frequently and avoid overwatering, which increases moisture and the likelihood of mold growth. If your plant is grown outdoors, be wary of heavy rainfall or humid weather, which can leave cannabis plants overly saturated. Another recommendation is to prune your plants regularly because dead, wet foliage can trap water and allow for the mold to grow on flowers or buds.


What is it

Coliforms are bacteria that are found naturally in animal and human digestive tracts that can spread to soil from tainted fecal matter or tainted water. E coli can live for weeks around cannabis plant roots and potentially transfer to the above ground surface of plants where it can live for up to 40 days, according to research by Purdue University. Plant E.coli can also invade your cannabis from other sources. For instance from an animal running loose in a field or by mixing young and old plants (that may be contaminated) after harvesting.

Even if your harvest is free from E coli, your final product may still become contaminated during the manufacturing or packaging process due to unwashed hands or dirty surfaces. In Spain, a recent study of the cannabis black market showed that dangerous levels of E.coli was present in nearly 90% of all samples tested. This study identified a serious need for coliform testing before going to market.

The health risks

If ingested or inhaled, E. coli can cause a host of illnesses ranging from diarrhea, fever, and vomiting to potentially fatal results in people who have weakened immune systems.

How to Prevent It

Harvesting your cannabis 40 days after seeds are planted can seriously reduce the risk of contamination. Another effective measure is to harvest your cannabis far away from animals and keep new and old plants separated.

During the manufacturing process, the best way to prevent E. coli contamination is to enforce strict hygienic standards. These methods will help, but the only way to be 100% sure is to test your plant and finished product.    

Aerobic Bacteria

What is It

Aerobic bacteria are microorganisms that thrive on oxygen. Although most people think of microorganisms as dangerous, they can actually serve an important purpose. In fact some aerobic bacteria can help cannabis grow and stave off other harmful bacteria, virus or fungus. But aerobic bacteria can also become dangerous at high levels, caused in part by pesticides, which transform into aerobic organisms as they degrade.

The Health Risks

At high levels, aerobic bacteria can be harmful, causing respiratory illnesses or fatal infections through direct inhalation. This is especially risky for medical marijuana patients with compromised health.

How to Prevent It

It’s impossible to completely prevent the occurrence of aerobic bacteria because it thrives on oxygen and most plants need oxygen around their roots. The best way to prevent dangerous levels of aerobic bacteria may be to reduce the use of pesticides. Finally, test your product with an accredited lab to be safe.


What is It

Enterobacteriaceae is a large family of bacteria that includes other harmful bacteria such as salmonella, shigella and yersinia. Unlike aerobic bacteria, these bacteria do not grow in oxygenated environments and can contaminate your crop through human or animal interaction.

The Health Risks

Like E.coli, the bacteria in this family can cause many types of illnesses, like allergic pneumonitis and other respiratory infections. Since these bacteria can be introduced by various sources, such as fecal matter or tainted soil, the risk of exposure often occurs during the production phase, as shown in the study from Spain.

How to Prevent It

Keeping your product as sanitary as possible – both in the growth phase as well as the production phase – can go a long way in preventing your product from becoming contaminated. The final step is to send a sample for testing.

ACS Testing Methods

At ACS, we utilize Real Time Polymerase Chain Reaction (qPCR) and Ultra Performance Liquid Chromatography (HPLC MS/MS) protocols. Using these technologies, we carefully inspect samples for specific bacteria and fungi DNA to differentiate microbes that are considered pathogenic (harmful) versus beneficial.

This technology is currently used in human genetic testing and pathogen detection in other agricultural commodities. It is considered the “gold standard” for microbial testing. qPCR testing provides fast and detailed reports that you can rely on.


All states require some form of microbiology testing for agricultural products and many have rules in place for hemp and cannabis. If you live in a state like California or Florida your Department of Health has already established stringent testing requirements. In this case, you’ll definitely want to work with a state verified lab like ACS who can test for specific strains of mold and publish the results.

But whether or not your state has an established hemp/cannabis program yet, we recommend you start testing your product for residual pesticides now. (link this to the other blog)

Tests You Can Trust:

When selecting a lab to test your hemp or cannabis, it’s important to look for labs with accreditations and third-party awards that prove the accuracy of their results. ACS is an ISO17025 accredited lab that has received multiple Emerald Badge awards for accuracy, including Microbiology testing awards.

We know how important it is to get the results right because selling a tainted product not only puts your company at risk of financial loss, it also puts your customers at risk of developing serious illnesses. ACS Lab will provide a testing service you can trust that will help you produce the highest quality cannabis and hemp products. For more information about what ACS Lab can offer, contact us and get started testing today.

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