Effects of Medium on the Results of Antimicrobial Sensitivity Testing
During the last decade several papers have been published about the influence of different components of the medium on the results of sensitivity testing of single antimicrobials, or single bacterial strains. The problem of the composition of the medium has not been treated as a whole, but rather as isolated items. Let us start with the agar. Agar is not a well-defined substance. It is very rarely composed exclusively of a neutral polysaccharide: agarose. In most cases it contains bound sulphate groups OSO 3 − which are able to bind particularly divalent cations such as Ca++ and Mg++. The content of cations and sulphate groups of the different agars varies from manufacturer to manufacturer and probably between the different lots of the same product (Barry and Effinger 1974).
KeywordsIonic Strength Inhibition Zone Sulphate Group Aminoglycoside Antibiotic Neutral Polysaccharide
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