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	While doing our antibiogram for 2006, we noticed on the Microscan that E.coli was only sensitive to Amp/Sulbactam 61% but sensitive to Augmentin 90%. We found that another local hospital had similar results. What causes that difference?
	Hi, While ampicillin/sulbactam and amoxicillin/clav are similar agents and have similar activities, there are commonly differences observed between AST results for the two agents. The most important one, in this case, is probably technical as many folks feel the concentration of the beta-lactamase inhibitors used in our in vitro testing are not equivalent. The other reason is the wonderful ability of our bacterial populations to have different susceptibilities to very similar agents. If you look in the CLSI M100-S17 tables published in January of this year, you will see that most of the "or"s in Table I have been removed. CLSI defined the criteria for "or"s and the "or" between amp/subactam and amox/clav was removed. This reflects the observations from several large databases of AST results using CLSI frozen reference tests that cross resistance and cross susceptibility between the agents do not meet the CLSI criteria.

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