Antimicrobial susceptibility testing at BCCM/LMG

In a clinical context, antimicrobial susceptibility testing is important to confirm susceptibility to chosen empirical antimicrobial agents or to detect resistance in individual bacterial isolates. However, as the problem of antibiotic resistance and its transfer is not restricted to the hospital environment, monitoring susceptibility to antimicrobials is also increasingly requested for non-pathogenic cultures used worldwide on a massive scale as starter cultures, probiotics, production strains, agricultural inoculants etc.

BCCM/LMG offers phenotypic antimicrobial susceptibility testing of lactic acid bacteria (LAB) and Bacillus as a customer service, according to the guidance document on the characterization of microorganisms used as feed additives or as production organisms (DOI: 10.2903/j.efsa.2018.5206) published by the European Food Safety Authority (EFSA).

Minimum inhibitory concentrations (MICs) are determined according to internationally recognized standards using serial twofold dilution procedures in broth, including relevant quality control strains.

AST analysis of LAB is performed at LMG according to the ISO 10932 standard (Milk and milk products - Determination of the minimal inhibitory concentration (MIC) of antibiotics applicable to bifidobacteria and non-enterococcal lactic acid bacteria (LAB)). AST analysis of Bacillus is performed according to the CLSI M07-A11 standard (Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically). AST is performed using a broth microdilution method and pre-coated microtiter plates, containing a variety of antibiotics, including those listed in Table 2 of the EFSA document for these taxa. Appropriate LMG strains are included as quality control strains to monitor the accuracy of the results. Per strain MICs are determined and reported for each tested antibiotic. Standardly, three independent tests are performed, to cover for possible variations.

The service report provided to our customers includes a detailed description of the methods used and the test results (MICs) in table format.

From April 2022, BCCM/LMG offers customers the possibility to extend the above service with a comparison of the MIC values of the tested LAB and Bacillus cultures with the appropriate EFSA microbiological cut-off values. The conclusions of this comparison are provided with the test results (MICs) in table format.



Rychen G, Aquilina G, Azimonti G, Bampidis V, Bastos M de L, et al. Guidance on the characterisation of microorganisms used as feed additives or as production organisms. EFSA J 2018;16:1–24. (DOI: 10.2903/j.efsa.2018.5206)