Why to use mueller hinton agar for antibiotic sensitivity test?

Answer 1

Better diffusion of antibiotics is just one reason why MHA is used for antibiotic sensitivity test (ABST). There are several factors that affect the ABST, they are: Disc concentration, diffusability of the drug, nature and composition of the medium, thickness of the medium, pH of the medium, potency of the disc. The pH should be between 7.2 and 7.4. If the pH is too low, certain drugs loose potency (eg. aminoglycosides, quinolones and macrolides) while certain others show excess activity (eg. tetracycline). If the pH is too high then reverse reactions would occur. Excess moisture too affects the reliability of the result. Increased thymidine reverses the inhibitory effect of sulphonamides, MHA has decreased thymidine content. Increased con. of Mg 2+ and Ca 2+ affects the results of aminoglycosides and tetracycline, also reduces zone size in case of P. aeruginosa. Decreased cation increases the zone size. Increased Zn would decrease the zone size of carbapenen group of antibiotics. Some fastedious organisms like Haemophilus sp, N.gonorrheae, S. pneumoniae, S. viridans and beta hemolytic Streptococcusrequire MHA supplemented with 15micro gram per ml NAD, bovine hematin and yeast extract.

Answer 2

the Mueller Hinton agar is used largely for testing antibiotic susceptibly of micro organisms. It helps to evaluate the resistance or susceptibility of a micro organism towards a particular drug (antibiotics). This helps in medical microbiology labs as it helps the doctors to decide on a plan of treatment or course of medication depending on the results of the susceptibility test.