A customer from canada reported out of range low results for internal quality controls (qc) in association with etest® daptomycin dpc 256 ww f100 (reference 535018) lot 1004343910.An investigation was performed.Testing was performed on retained samples of etest daptomycin dpc 256 ww f100 (lot 1004343910) and etest daptomycin dpc 256 s30 (lot 005932460), in parallel with another batch as a reference (lot 1006198630).Three qc strains were tested: staphylococcus aureus atcc 29213 and enterococcus faecalis atcc 29212 were tested on two mueller hinton media: one lot of mh-e biomérieux and one lot of mh-bd pre-poured.Streptococcus pneumoniae atcc 49619 was tested on one lot of mh blood, produced in-house with bd powder.The customers issue was reproduced with: - staphylococcus aureus atcc 29213: lot 1004343910 and mh-e media had two strips on three at 0.125 ¿g/ml - enterococcus faecalis atcc 29212: all three lots and mh-e media had one or two strips on three at 0.5 ¿g/ml.All data was compliant with: - streptococcus pneumoniae atcc 49619 on mh blood (produced in-house with bd powder.- staphylococcus aureus atcc 29213 and enterococcus faecalis atcc 29212) on mh-bd prepoured as explained in the etest customer information sheet cis 014, daptomycin requires physiologic levels of free calcium (ca2+) for expression of adequate activity.The bioavailable free ca2+ levels in brands and batches of mha powder and commercial mha plates can vary significantly and affect etest dpc results.Conclusion: no loss of performance was found during the investigation.However, it was confirmed that the source of the media could impact the reading of the mic value.This doesn't mean that particular media are not compatible with etest but that the composition is different.Mic values may vary batch to batch and it is important to test qc strains to validate the use of the lot of media.
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