Description
Mueller Hinton Agar is the medium recommended by WHO,1 in conjunction with the U.S. Food and Drug Administration (FDA)2 and the National Committee for Clinical Laboratory Standards (NCCLS)3,4, for the performance of agar dilution and disc diffusion antibiotic susceptibility testing of the majority of rapidly growing aerobic and facultative anaerobic micro-organisms.
Amyl Mueller Hinton Agar AM 102, conforms with the recommended NCCLS standard for Mueller Hinton agar in that it contains low levels of thymine and thymidine, factors which adversely affect the testing of sulphonamides and trimethoprim,5 and appropriate levels of calcium and magnesium ions, factors which can influence the MIC of aminoglycoside antibiotics against Pseudomonas aeruginosa and tetracyclines against certain species of staphylococci.6.7.8 Each batch of Amyl Mueller Hinton agar is tested against Enterococcus faecalis ATCC 29212 and Pseudomonas aeruginosa ATCC 27853 to ensure it’s suitability for susceptibility testing against trimethoprim and sulphonamides and for MIC determinations of aminoglycosides against Pseudomonas aeruginosa. Supplementation of Mueller Hinton agar with 5% defibrinated horse or sheep blood, sometimes required for the growth of more fastidious organisms, may influence the activity of certain antibiotics and appropriate controls would be required therefore, to monitor that variable.12 Supplementation with bovine haematin (15μg/ml), NAD (15μg/ml) and yeast extract (5mg/ml) is used for testing Haemophilus spp.12 The addition of 10% lysed horse blood as an enrichment and as a source of thymidine phosphorylase12 may be useful but is not necessary for the latter purpose because of adequate levels of thymidine phosphorylase in Amyl Mueller Hinton Medium AM102.
