A united states customer reported a misidentification of 2017 cap d-10 isolate of propionibacterium granulosum as peptostreptococcus anaerobius and unidentified when testing with the vitek® 2 anc test kit.An internal biomérieux investigation was completed.There was no strain or raw data submitted by the customer for evaluation.This cap sample was a simulated joint tissue from an elderly patient following hip replacement surgery.The challenge sample also contained s.Epidermidis.The specimen was not graded due to lack of participant and referee consensus.Referees demonstrated 49.2 % and participants 56.2 % consensus for correct identification of all organisms.The biomérieux internal cap d-10 strain was rehydrated and sub-cultured under anaerobic conditions.Testing included individual organism suspensions on anc cards from four different lots, in duplicate and the vitek® ms.The eight anc cards tested resulted in low discrimination identifications of multiple clostridium species, not the expected result.The vitek® ms resulted in the expected identification of p.Granulosum with a 99.5% confidence value.Review of customer's results against expected reactions for p.Granulosum demonstrated several atypical negative reactions (ellm, pyra, arg, pvate, amani, drib).Many participants additionally entered atypical positive morphology (cocci) according to the anc knowledge base all contributing to the misidentification.An increased number of atypical negative results can indicate a strain with decreased viability, user set up error or an atypical strain.This is an atypical strain.
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