An investigation was initiated in response to a customer complaint of false susceptible meropenem results for enterobacter cloacae complex in association with the etest® meropenem mp 32 ww b30 (ref 513800, lot 1007496370).The isolate was collected from a patient urine specimen.1.Retained samples analysis: retain samples for the customer's lot number 1007496370 were investigated and tested in parallel with a reference lot number 1007900020.Conformance to specifications was verified with the following atcc quality control strains that were also tested to release etest mp32 strips: atcc 25285 bacteroides fragilis, atcc 49619 streptococcus pneumoniae, atcc 49766 haemophilus influenzae, atcc 27853 pseudomonas aeruginosa, atcc 25922 escherichia coli.The etest® mp32 performance of the impacted lot and the reference lot number comply with the specifications.2.Analysis of provided strains: the customer submitted the strain for investigational testing.The received strain was verified to be enterobacter cloacae complex with the vitek® 2 gn id test kit.The strain was tested by the agar dilution (ad) method and broth micro dilution (bmd) method since ad was the method used for the etest mp32 strips development and bmd was the method used for meropenem drugs development in ast-n248 and ast-n387 cards used by the customer.Eucast clinical 2020 breakpoints were applied.Ad: mic = 2 mg/l (susceptible), bmd: mic = 16 mg/l (resistant), etest mp 32: mic = 4 mg/l (intermediate) on both lots.3.Results analysis: the customer's susceptible results were not reproduced internally.Etest mp32 mics are within essential agreement compared to the reference mics (ad) but lead to minor errors or category.The reference mic (ad) is on the breakpoint (mic = 2 mg/l s) so within one doubling dilution, mic interpretation can shift from s to i.This strain is a borderline strain for meropenem.4.Complaint trend analysis: no other complaints were registered for etest mp32 lot number 1007496370.5.Conclusion: the investigation concluded that the customer's lot 1007496370 is performing in accordance with specifications.The customer's susceptible results were not reproduced internally.Etest mp32 mics are within essential agreement compared to the reference mics (ad) but lead to minor errors or category.This strain is a borderline strain for meropenem.
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