09.12.2022

FAA medium for disk diffusion of anaerobe bacteria

EUCAST disk diffusion of anaerobe bacteria and the FAA-HB medium.

EUCAST disk diffusion of anaerobe bacteria (Bacteroides spp., Prevotella spp., Fusobacterium necrophorum, Clostridium perfringens and Cutibacterium acnes) is performed on Fastidious Anaerobe Agar. FAA is available from several manufacturers, both as a powder for in-house production in laboratory media-kitchens, and as commercially available pre-poured plates. The EUCAST FAA-HB consists of FAA with 5% mechanically defibrinated horse blood without other additives. The agar depth is important and when buying pre-poured plates, make sure to check. The variation (±0.5 mm) around the prescribed agar depth (4 mm) is to allow random variation within and between plates, but the average of repeat measurements should meet the prescribed depth of 4±0.5 mm and all individual measurements inside the range 3.5 - 4.5 mm. This meets the EUCAST general rule for all plates for disk diffusion. QC criteria are available from EUCAST (www.eucast.org) – be sure to check your plates before introducing them for disk diffusion in the lab. The addition of 5% mechanically defibrinated horse blood is identical to the procedure used for the production of MH-F plates.

Note, plates for susceptibility testing with FAA media may not be interchangeable with FAA plates already used in the lab for culturing anaerobic bacteria.