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	We have a Vitek 1, we isolated a Klebsiella pneumoniae ESBL positive on Vitek. We did the confirmatory testing using Ceftazidime/Ceftazidime-clavulanic and Cefotaxime/Cefotaxime-clavulanic. The test was negative for ESBL. Should I report this isolate out as ESBL negative and change the expert rules on Vitek so that the cephalosporins are susceptible? The expert rules change the cephalosporins regardless of MIC if the VItek ESBL is positive.
	If the CLSI ESBL disk confirmatory test is negative then you should consider the isolate as ESBL negative. Vitek legacy will give false positive and false negative ESBL confirmatory tests on some occasions. Suggest you contact the bioMerieux Technical Support and report the problem. It will help if you save the organism and send to them for further investigation. Just because the ESBL test is negative, it doesn't mean necessarily that all the 3rd generation cephalosporins are susceptible. The Klebsiella strain may have acquired a plasmid-mediated ampC in which case the ESBL test could be negative and the cephalosporins still resistant. Recommend that you repeat the susceptility using a CLSI approved method either disk diffusion or microbroth MIC. Use the result you obtain from the reference method to determine the final susceptibility that is reported.

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