In short
- CFU/g means colony-forming units per gram: the number of living bacteria that grew from one gram of food.
- Some pathogens are judged as present or absent in 25 g, others against a number.
- Always check which text the lab used for its limits, then record your action.
A lab report can look like a bill from a foreign country. It is easier than it seems. Here are the parts that matter.
The header
Sample name, date and time of sampling, date of reception, temperature on arrival and the dates of analysis. If the sample arrived warm, say so and ask the lab how that affects the result.
Units
- CFU/g: colony-forming units per gram of food. A result of 103 means about a thousand per gram.
- CFU/cm²: per square centimetre of surface.
- Absence in 25 g: no bacteria were found in a 25 g portion. It is the usual rule for Salmonella.
- < 10: below the detection limit of the method.
Methods
You will see references such as ISO 4833-1 (total count), ISO 16649-2 (E. coli), ISO 6579-1 (Salmonella), ISO 11290-1 (Listeria) and ISO 6888-1 (Staphylococcus aureus). They tell you which standard method the lab followed. An accredited laboratory also shows its ISO 17025 accreditation number.
Limits and verdicts
The report compares each result with a criterion, and the criterion comes from somewhere. For some pathogens it is a legal text. In the EU, Regulation (EC) 2073/2005 sets limits such as Salmonella absent in 25 g for certain foods and Listeria monocytogenes of 100 CFU/g or less in ready-to-eat foods that cannot support its growth. For many ordinary indicators, such as the total count on a cooked dish, the thresholds come from professional guides or the lab's own reference values. Three verdicts are common:
- Satisfactory: no action.
- Acceptable: tolerated, but look at the cause.
- Unsatisfactory: act now.
Always ask which text or guide the lab used. If it is not on the report, it should be.
What to do with a bad result
- Isolate and stop serving the dish or batch if it is still in stock.
- Find the cause: temperature, cooling time, cross-contamination, a person, a supplier.
- Correct it, then clean and disinfect.
- Retest to prove the fix.
- Write the date, the cause and the action in your records.
A pathogen result (Salmonella or Listeria) is an emergency. Contact your authority and follow its instructions, especially if people have been served.
This article is general information, not legal advice. Rules and limits change: confirm the current text with your food safety authority (ONSSA in Morocco, your national authority in the EU) and with your accredited laboratory.
Questions
What does CFU/g mean?
Colony-forming units per gram. It counts living bacteria that formed a visible colony when a gram of food was grown in the lab.
What does absence in 25 g mean?
The lab tested a 25 g portion and found none of that bacterium. It is how Salmonella is usually judged.
Who sets the limits on my report?
Sometimes a legal text such as Regulation 2073/2005 in the EU. For many indicators it is a professional guide or the lab's reference. Ask the lab to name the source.
