Food microbiology: The best microbial QC strains

In recent years, standards have increasingly encouraged food microbiology laboratories to use strains as reference materials. These strains can be used for method verification, culture media performance testing, or technician qualification.

In addition to having a significant cost for the lab, these strains are not always easy to manage.

Fortunately, there are microbial QC strains suppliers that have developed strain formats suitable for food laboratories… The challenge is finding them!

To make your task easier, we surveyed the SuperMicrobiologists (over 9000 subscribers) to find out which QC control strain suppliers they prefer.

Here is their response.

Summary:

• Quantitative QC strains
  • Vitroid and Lenticule
  • BAControl
• Qualitative QC Strains
  • BACuali

Take part now in the Survey for 2025

Quantitative quality control strains

The advantage of using calibrated strains is that you know exactly (or almost… it’s still microbiology!) the number of microorganisms you have in your sample (per pellet, per ml, or per 100uL).

After a short preparation step, you can inoculate your sample, being sure that you’re not mistaken in the target. There is nothing worse than invalidating a test because you put too many or too few microorganisms.

Here are the SuperMicrobiologist’s preferred suppliers of quantitative QC strains (bacteria, yeast and mold) :

Vitroid and Lenticule from Merck

Control strains from the English NCTC (National Collection of Type Cultures) collections for Lenticules and Spanish CECT (Colección Española de Cultivos Tipo) for Vitroids.

Lenticules and Vitroids are available in different concentrations: < 100, between 1000 and 10,000, and >10,000 CFU. For each strain, a CoA (Certificat of Analysis) gives the exact concentration of the sample.

To prepare the strain, you must place the water-soluble disc (tablet) directly on the surface of the culture media and wait 10 seconds.

Strengths of Lenticule and Vitroids:

• Simple 1-step preparation
• 2 possible uses: 1 tablet on the plate or 1 tablet in a diluent for several tests.
• Expiration 36 months from manufacture, with a minimum of 12 months at delivery.
• Maximum 3 passages compared to the reference strain.
• WDCM equivalence

Link to Lenticules and Vitroids

Merck contacts – Tell them you’ve come from SuperMicrobiologists 😉

BAControl from Ielab

BAControl is a quantitative strain format, with strains from the Spanish CECT microbial collection (Colección Española de Cultivos Tipo).

Ielab offers 3 levels of concentrations <100, between 100 and 1000, and > 1000. For each strain, a certificate of analysis gives the exact concentration of the pellet.

Preparing the strain involves 3 steps: Initially, the tablet is dissolved in 20 ml of sterile water. This is followed by a waiting period of 10 minutes, during which the solution should be vortexed every 2 minutes. After this interval, the strain is ready for use.

Strengths of BAControl:

• Stable suspension 8 hours after rehydration.
  
• Expiration 12 months from manufacture, with a minimum of 6 months at delivery.
  
• WDCM correspondences available.
  
• After rehydration, a considerable number of tests are available (e.g., rehydration in 20 ml = 200 aliquots of 100 ul available)

Link to BAControl catalog

ielab distributors contacts
ielab contact – Tell them you’ve come from SuperMicrobiologists 😉

Qualitative Quality Control Strains

Non calibrated (qualitative) strains are used to feed the strain bank of food microbiology laboratories. Then the strains could be used to control an identification system, the performance of a culture media, to qualify a technician or as a positive control.

Here are the SuperMicrobiologist’s preferred suppliers of qualitative strains:

BACuali from Ielab

Bacuali is a format of qualitative QC strains from the Spanish CECT collection (Colección Española de Cultivos Tipo).

The pellet is resuspended in 20 ml of sterile water, and after 10 minutes, the strain can be used for manipulation.

Strengths of BACuali:

• Expiration 12 months from manufacture, with a minimum of 6 months at delivery.
• WDCM correspondences available.

Link to BACuali

ielab distributors contacts
ielab contact – Tell them you’ve come from SuperMicrobiologists 😉

Epower and Kwik Stik strains from Microbiologics, and Bioball from bioMerieux have also been mentioned by the SuperMicrobiologists

Now you have all the information you need to choose the strain supplier that best suits your lab. Let us know in comment which one you choose!