How Cannabis Is Tested for Microbes and Why It Matters

Written by Lorien Strydom

November 27th, 2025

Microbial testing in cannabis detects harmful pathogens like Aspergillus species and Salmonella, plus quality indicators like total yeast and mold, using culture-based and molecular methods to meet state requirements that vary significantly across the US.

Labs test to ensure product integrity and regulatory compliance, though the specific targets and limits depend on which state program applies.

If you've ever felt confused looking at a Certificate of Analysis (COA) or wondered why test results differ between states, you're not alone.

Important legal note: Mood cannot provide health or safety advice. Testing is performed by independent third-party labs, and COAs document lab findings for transparency.

Table of Contents

• Why Cannabis Products Get Tested for Microbes

• US Testing Requirements Vary by State

• What Shows Up on a Cannabis Lab Report

• How Labs Detect Microbes in Cannabis

• What Makes Lab Results Trustworthy

• Reading the Microbial Section of a COA

• For Operators Who Want More Detail

Why Cannabis Products Get Tested for Microbes

Cannabis cultivation and processing create conditions that favor microbial growth. Warm, humid environments support bacteria and fungi naturally, which means product integrity requires attention throughout the supply chain.

Testing serves as quality assurance and helps producers meet regulatory compliance requirements where they exist. Inhalable products receive particular scrutiny because material is drawn directly into the lungs, making contamination control especially important for this category.

For Mood's testing process , we work with independent laboratories that screen for unwanted materials including mold growth, residual solvents, pesticides, and microbes.

Every Mood product comes with a batch-specific COA accessible via QR code on packaging, documenting what third-party labs found during testing—whether you're exploring THC drinks or other formats.

This isn't about making wellness claims or positioning ourselves as a health authority.

We simply can't provide health or safety advice legally. What we can do is share test results transparently so you understand what you're purchasing.

US Testing Requirements Vary by State

The United States operates on a patchwork of state-specific rules rather than a single federal standard.

Each state with a regulated cannabis program sets its own microbial testing requirements, which creates significant variation in what gets tested and what passes.

Two primary models emerge across state programs, and understanding them helps decode COA results from different sources.

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California's Zero-Tolerance Model

California requires the absence of six specific targets for inhalable cannabis products. Labs test for four Aspergillus species: A. flavus, A. fumigatus, A. niger, and A. terreus, plus Salmonella species and Shiga toxin-producing E. coli.

Results show as "not detected" or "detected." There's no allowable limit. Licensed producers must use accredited third-party labs, and products that test positive cannot be sold as inhalables.

Massachusetts' Indicator-Limits Model

Massachusetts sets numeric thresholds for broader quality indicators rather than targeting specific pathogen species. The state requires counts for total aerobic bacteria (maximum 10⁵ CFU/g), total yeast and mold (maximum 10⁴ CFU/g), and specific limits for coliforms and bile-tolerant gram-negative bacteria.

COAs display the measured count alongside the state limit. A reading of 8.2 x 10³ CFU/g for total yeast and mold passes comfortably under the 10⁴ threshold, for example.

The Hemp Market Gap

Hemp-derived products operating under the 2018 Farm Bill typically face voluntary testing rather than mandatory state requirements. Testing becomes a choice that signals quality rather than a compliance mandate with penalties for failure.

Batch-to-batch variability can occur when regulatory oversight varies or doesn't exist.

Brands like Mood provide batch-specific COAs even when not legally required, using testing as a transparency tool in markets where many competitors skip comprehensive safety screening.

Mood offers millions of users hemp-derived THC, which is 100% legal and fully compliant cannabis.

You may have heard that the legality of hemp-derived THC is currently under attack, which could threaten the wellness of so many. Read here to learn how to join the fight, and help us keep hemp cannabis accessible to all for a long time to come.

What Shows Up on a Cannabis Lab Report

COAs split microbial results into two categories: specific pathogens that trigger zero-tolerance rules in some states, and quality indicators that describe general contamination levels through numeric counts.

Pathogens Often Targeted in State Programs

Four Aspergillus species (A. flavus, A. fumigatus, A. niger, A. terreus) appear on many state-required pathogen panels for inhalable products. These organisms signal process hygiene issues during cultivation or handling.

Salmonella species represent bacterial pathogens that state programs frequently include in mandatory testing protocols. Detection indicates contamination that makes products unsaleable in regulated markets.

Shiga toxin-producing E. coli rounds out common pathogen panels in states with comprehensive microbial requirements. Like other specific targets, STEC detection means product fails and cannot reach consumers through legal channels.

Quality Indicators Describing Cleanliness

TYM (Total Yeast and Mold) measures fungal contamination levels through colony counts. States using numeric limits typically set thresholds like 10⁴ CFU/g as acceptable maximums. Results below this pass, while higher counts indicate spoilage risk or process problems.

APC (Aerobic Plate Count) indicates general bacterial populations present in the sample. This quality indicator reflects sanitary conditions during production, with Massachusetts setting 10⁵ CFU/g as its maximum allowable level.

Coliforms and bile-tolerant gram-negative bacteria serve as additional quality indicators. These measurements describe overall cleanliness rather than identifying specific dangerous organisms.

Advanced Points Competitors Miss

Water activity (Aw) limits inhibit microbial growth when set correctly. Some states establish thresholds like 0.65 for dried cannabis or 0.85 for solid edibles, recognizing that lower moisture availability prevents contamination.

Clostridium botulinum spores get discussed in regulatory guidance but rarely appear as mandated targets. Protocol challenges make routine testing difficult, which explains why this organism receives less attention despite its theoretical relevance.

How Labs Detect Microbes in Cannabis

Testing laboratories use different method types depending on what they're measuring and which state requirements apply. Understanding the tradeoffs helps interpret COA results and recognize why different labs might choose different approaches.

Culture-Based Methods

Culture-based enumeration grows organisms on selective media, allowing labs to isolate and count colonies. This traditional approach offers organism confirmation and lower per-test costs while using established protocols that regulatory bodies trust.

The process takes longer than molecular alternatives and can miss viable but non-culturable cells that don't grow under standard plate conditions. Competition on plates sometimes obscures true counts when fast-growing organisms dominate.

Labs use culture methods for generating numeric counts like TYM and APC, plus for confirmation testing when presumptive positives need verification.

Molecular Testing Through qPCR

Quantitative PCR detects pathogen DNA directly, delivering faster results than waiting for colonies to grow. The method offers sensitive detection that identifies stressed cells culture methods might miss.

However, qPCR detects DNA from dead cells unless labs include free DNA removal steps. Enrichment still gets needed for many workflows, and per-test costs run higher than basic culture approaches.

State programs often specify qPCR for targeted pathogens like Aspergillus species, Salmonella, and STEC where speed and species-level identification matter more than cost.

Critical Testing Realities

Cannabis matrices inhibit assays naturally, requiring purification reagents before accurate testing. Plant compounds interfere with both culture growth and molecular detection unless properly removed during sample preparation.

Presumptive positives on qualitative screens require confirmation with a different method, not just retesting the same enrichment. This confirmation requirement prevents false positives while meeting regulatory standards for reliability.

Method selection depends on product type, route of use, and applicable state requirements. There's no universal "best" method, only fit-for-purpose choices that balance speed, accuracy, and cost.

Other Method Notes

Chromogenic media provides a fast, visual, economical culture option that some labs prefer for routine screening. Next Generation Sequencing (NGS) offers complete microbiome analysis but serves research and investigation purposes rather than routine compliance testing.

What Makes Lab Results Trustworthy

Several credibility markers help distinguish reliable testing from labs that cut corners or lack proper oversight. COAs from trustworthy sources include signals that confirm competent analysis.

ISO 17025 Accreditation

This international standard signals lab competence and quality management systems. Accredited facilities demonstrate technical proficiency and maintain protocols that ensure reliable results across time.

Validated Method Toolbox

Reputable labs use methods from AOAC, ISO, USP, FDA, or USDA references. Cannabis testing applies validated or verified methods rather than improvised protocols that lack supporting documentation—the same rigorous approach used for potency testing.

Method Suitability and Sample Prep

Method selection depends on product type like flower versus edibles versus concentrates. Route of use matters too, since inhalable products face different requirements than ingestibles.

Standardized sample preparation proves critical because cannabis matrices trap microbes. Proper grinding, weighing, and extraction ensure accurate detection rather than missing contamination hidden in plant material—whether testing edibles or flower.

Controls and Quality Assurance

Labs use certified QC strains to verify method performance consistently. Environmental monitoring supports Good Manufacturing Practices by catching facility-level contamination sources.

 Mood partners with established labs including New Bloom Labs in Tennessee and Marin Analytics. Every product gets batch-specific testing, with COAs accessible via QR codes on packaging.

This documents third-party findings transparently rather than relying on in-house testing that might create conflicts of interest—ensuring the potency and safety you see on labels reflects reality.

Reading the Microbial Section of a COA

Understanding what different COA formats mean transforms confusing lab reports into useful decision-making tools. The presentation varies by testing approach and state requirements.

California-Style "Not Detected" Results

Pathogen panels show ND (Not Detected) or PASS when zero-tolerance targets don't appear in testing. An Aspergillus species line reading "Not Detected" means the product passed that specific requirement.

This format reflects absence testing rather than quantification. Either the target appears or it doesn't, with no middle ground.

Massachusetts-Style Numeric Counts

Quality indicators show measured counts alongside state limits.

A line reading "TYM: 8.2 x 10³ CFU/g (Limit: 10⁴ CFU/g) - PASS" demonstrates the product contains 8,200 colony-forming units per gram, well below the 10,000 maximum.

Numbers represent actual measured contamination levels. Lower counts indicate cleaner products, while results approaching limits suggest process improvements could help.

Key COA Elements Worth Noting

Batch-specific identification ties each COA to a particular production run. Lab information including accreditation status and testing methods used provides credibility context. Test dates indicate when analysis occurred, which matters for product freshness and quality .

Water activity values often appear as Aw readings like 0.58 for dried flower. Lower values prevent microbial growth by reducing available moisture. Common thresholds include 0.65 for dried cannabis and 0.85 for edibles.

Presumptive Positive to Confirmation Sequence

Initial screens flag potential presence but aren't definitive. Confirmation testing uses a different method to verify the presumptive finding. Final results determine pass or fail status.

The critical point: labs cannot just retest with the same method. Confirmation requires methodological diversity to ensure accuracy.

Hemp Market Reality Check

Testing remains voluntary in most Farm Bill hemp markets rather than mandatory. Batch-to-batch variability can occur when regulatory oversight doesn't exist or enforcement stays minimal.

Transparent brands provide COAs even when not required, using testing as a quality signal.

Mood's product verification system allows confirmation of the specific lot you're consuming, which matters more in voluntary testing environments where some competitors skip comprehensive screening entirely.

For Operators Who Want More Detail

Implementation-focused readers benefit from specifics about testing protocols and automation options that make routine screening more efficient.

Common Testing Media and Protocols

Labs use Cetrimide Agar for detecting Pseudomonas aeruginosa and Baird-Parker medium for Staphylococcus aureus identification. CHROMagar Candida helps identify fungal species through chromogenic reactions.

Heat-shock steps enable spore count detection by killing vegetative cells while leaving resistant spores viable.

Aspergillus identification through morphology carries misidentification risks. Gene sequencing or validated qPCR assays provide more reliable speciation, which matters when state rules target specific Aspergillus types rather than the genus broadly.

Automation and Quality Control

Liquid handlers automate extraction and qPCR setup, reducing manual error and increasing throughput.

Integrated PCR platforms streamline workflows from sample prep through result reporting.

ATP hygiene checks provide fast sanitation feedback for facility cleanliness monitoring. DNA removal steps prevent false positives in molecular testing by eliminating genetic material from dead cells.

Certified QC strains verify method performance consistently across testing runs. These reference materials ensure detection capabilities stay within acceptable ranges.

Method selection balances speed, cost, and accuracy through fit-for-purpose choices.

Culture methods maintain enduring value for confirmations and counts, while qPCR excels at targeted pathogen detection where rapid results matter.

Putting This Into Practice

Microbial testing in cannabis isn't one standard but many state-specific approaches.

Understanding the California zero-tolerance model versus Massachusetts numeric limits provides a mental framework that makes most COA formats interpretable.

You now recognize what TYM, APC, and Aspergillus species lines mean when you encounter them.

Water activity values make sense as contamination prevention measures. Presumptive positives requiring confirmation through different methods explains why retesting alone doesn't satisfy regulatory requirements.

In hemp markets where testing stays voluntary, transparency becomes a differentiator. Brands that test comprehensively and share results publicly signal quality commitment even without mandatory oversight forcing their hand.

Check the COA for whatever cannabis product you currently have. Scan that QR code. Review the microbial section with your new understanding.

Notice which testing model the lab used and whether results fall comfortably within limits or approach thresholds.

Batch-specific testing matters because contamination varies between production runs.

A clean test on one batch doesn't guarantee the next batch will perform identically. This reality makes ongoing testing valuable rather than treating one good result as permanent validation.

The best COAs come from accredited labs using validated methods with clear documentation. Look for ISO 17025 accreditation.

Check which specific methods the lab used. Verify the test date shows recent analysis rather than old results from months ago.

For Mood's full product line , we maintain this testing transparency across flower, edibles, vapes, and pre-rolls. Every batch gets independent third-party analysis, with results accessible to verify exactly what you're purchasing.

You're now equipped to read cannabis COAs confidently and understand why testing requirements vary so dramatically between jurisdictions. That confusion you felt initially?

It came from a genuinely confusing regulatory landscape, not from your inability to understand technical content.