Dr. Janet Liu, Ph.D. is the Director of Microbiology at Emery Pharma. In this video she gives an overview of the European Food Safety Authority’s guidance on antimicrobial testing of microbes used in animal feed.
Slide 1: Hello everyone! My name is Dr. Janet Liu, and I am the Director of Microbiology at Emery Pharma. Today I will be giving a brief overview of the European Food Safety Authority’s guidance on antimicrobial susceptibility testing of microbes used in animal feed.
Slide 2: Within the European Union the ESFA is the agency responsible for providing advice, risk assessment, and guidance on matters related to the food supply chain. EFSA has created a scientific panel that offers advice and guidance on additives and products or substances used in animal feed. The name of this scientific panel is the Panel on Additives and Products or Substances used in Animal Feed—abbreviated FEEDAP.
Slide 3: The guidance document that we will be discussing in this presentation is the “Guidance on the characterization of microorganisms used as feed additives or as production organisms”. Additives include familiar products, such as Lactobacillus species, commonly found in fermented foods such as yogurt, to less familiar products, such as microbial-produced enzymes like amylase. This document serves to support applicants in the submission of microbes or microbial product additives for use in animal nutrition. Although the EFSA FEEDAP guidance is generated for-and-by members of the European Union, each individual country within the Union may have additional guidance and requirements.
Slide 4: There are many different requirements in the FEEDAP guidance, listed in Table 1. For bacteria, this includes Identification, Antimicrobial susceptibility, Antimicrobial production, and Toxigenicity and pathogenicity.
Slide 5: In this presentation we will only be focusing on section 2.2, “Antimicrobial susceptibility”, specifically subsection 2.2.1, “Phenotypic testing”. This section is applicable for live bacteria and bacteria fermentation derived products used in feed additives.
Slide 6: Antimicrobial susceptibility testing is the determination of the susceptibility of a microbe to an antimicrobial agent, such as an antibiotic. This information is important for limiting the spread of antibiotic resistance from feed additive microbes to microbes that have colonized humans and animals, which can render important antibiotic drugs used to treat infections unusable. Antimicrobial susceptibility is assessed by determining the Minimum Inhibitory Concentration (MIC) of an antimicrobial agent against a microbe. With regards to microbes used in feed additives, the applicant is required to determine and submit the MIC of their organism against a panel of antimicrobials.
Slide 7: To fulfill the requirements of the EFSA FEEDAP guideline, MIC testing should be performed according to internationally recognized standards, such as Clinical and Laboratory Standard Institute (CLSI).
Slide 8: MIC determination should utilize a broth or agar-based serial dilution method, with MIC values expressed as milligram per liter or microgram per milliliter; qualitative or semi-qualitative assessments, such as zone of diffusion methods, are not accepted.
Slide 9: Of the acceptable methods, Emery Pharma utilizes the broth microdilution method, which is well suited for testing multiple antimicrobials against a test organism at the same time. The procedure for the microdilution method is depicted in the schematic shown in the slide. In Step 1, the antimicrobial—in this case, a set of antibiotics to be tested—are 2-fold serially diluted in a 96-well microdilution plate. In Step 2, the bacteria being assessed is collected from an agar plate with a sterile swab and a suspension is prepared. The serially diluted antibiotics and the bacteria suspension are combined in Step 3. After incubation, the MIC is determined in Step 4 by checking the 96-well plate for bacteria growth, either by eye or by using a spectrophotometer. The MIC is defined as the lowest concentration of an antimicrobial that inhibits bacterial growth.
Slide 10: At Emery Pharma we often have clients that request antimicrobial testing against their bacterial feed additives.
Slide 11: Shown in the current slide is the table listing the required antimicrobials to be tested for various microorganisms, as required by the EFSA FEEDAP guideline.
Slide 12: The table also lists the MIC cut-off values for the various combinations of antimicrobials and bacteria. The MIC cut-off values serves as a guide to determine whether the bacteria being assessed is susceptible or resistant to an antimicrobial agent and are defined based on published data. Although a total of 13 different antimicrobials are listed in Table 2, not all are required for MIC testing and determination against all species, and are shown in the table as “n.r.” for “not required”. However, if a specific antimicrobial MIC-cut off value is listed for a microorganism, then that antimicrobial must be tested.
Slide 13: For example, Bacillus species are not required to be tested against Ampicillin, Tylosin, Ciprofloxacin, Colistin, and Fosfomycin…
Slide 14: …While Colistin is the only antimicrobial required for testing for any bacteria in the family Enterobacteriaceae.
Slide 15: For species not listed in Table 2, the EFSA FEEDAP panel recommends testing Gram-positive organisms against the antimicrobials listed for “Corynebacterium and other Gram-positive” …
Slide 16: …And in the case of Gram-negative organisms, against the antimicrobials listed for “Enterobacteriaceae”. The resulting MIC values should then be compared to what has been published in the literature for that specific or related species.
Slide 17: At Emery Pharma our scientists have extensive experience in antimicrobial susceptibility testing and follow CLSI guidelines. To find out about how we can help you conduct EFSA FEEDAP required MIC testing for your microorganism, please contact us through our website, at www.emerpharma.com or call us at 1-888-98-EMERY.