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We use ETEST strips for susceptibility testing on request for Strep species. How do you interpret the MIC when the etest concentrations do not coincide with CLSI breakpoints? (ex. a Strep sp. (not S. pneumo) has growth either up to the 0.125 concentration or between 0.094 and 0.125 (which we would round to up). The CLSI breakpoints are <=0.12 sus and 0.25-2 intermediate.
Thanks for your interest in ASM's Askit. I would consider 0.125 and 0.12 to be the same. The dilutions used are halving dilutions and if you were to carry out the 0.12 concentration to 3 places right of the decimal, it would be 0.125. Also, even if the concentrations were exactly 0.120 and 0.125, the difference between 0.125 and 0.12 is too small to be significant in MIC systems. In your example, both concentrations would be considered susceptible. We hope that we were able to answer your question. Please visit us again at the American Society for Microbiology. DISCLAIMER Askit is for general information purposes only and may not be relied upon by users for decisions or action in specific circumstances. Neither ASM nor the expert assures the accuracy or completeness of information provided. Questions are answered based on current information, which may change over time. Please note the date that a question was answered. If an answer is more than one year old, you may want to resubmit the question for an updated answer. The advice and comments do not necessarily reflect the views of ASM. ASM and INDIVIDUAL experts expressly disclaim any and all liability for any direct, indirect, or special damages or loss of any nature incurred as a consequence of use of this site or any advice or comment by any expert. By using Askit, the user accepts the waiver of claims and all terms of use of ASM’s site, including the disclaimers set forth in the “Legal Rights” link on ASM’s home page.
 
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