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A customer in (b)(6) notified biomérieux of a false negative result in association with the bact/alert® fa plus culture bottle and the bact/alert® 3d instrument (ref.200290, serial #: 601cr5641).The customer loaded two bottles from one patient on 22nov2019.The first bottle had a positive result on 25nov2019, and the second bottle incubated for five (5) days with a negative result.Both bottles are from the same lot (ref#: 410851, lot#: 4052663).The blood culture from the first bottle with the positive result was subcultured on cos, emb, pvx (rta brand), and the growth showed that it was a candida species.The bottle isolate was then tested on vitek® 2 compact with the vitek 2 yst card, and the result showed that it was candida ciferii.The second bottle with the negative result was inoculated onto rta chromogenic candida agar and showed growth determined to be of the candida species.The grown microorganism was also tested on the vitek 2 yst card and identified as c.Ciferii.The customer reported that the patient was not harmed or treated incorrectly due to the discrepant result.The patient had two bottles, one which flagged as true positive, and the error was noticed by the microbiologist.A biomérieux internal investigation will be initiated.
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On (b)(6) 2019, a customer in (b)(6) reported a false negative result was obtained for a patient sample in association with the bact/alert® 3d instrument system (ref.200290, serial #: (b)(4)).The customer reported two bact/alert fa fan plus bottles were loaded from the same patient, one bottle turned positive and one negative.The customer sub-cultured the negative bottle, and candida ciferri was recovered.An internal biomérieux investigation was performed; which included a review of the data submitted by the customer.The investigation team extracted and re-ran the bottle readings with the gcs algotool, and the bottle was negative at 5.14 days.The investigation determined that the graph appeared as a true negative with a slow upward rise due to the blood sample on the gcs algo tool.The readings were forwarded to biomath for additional evaluation.Per biomath feedback, the algotool flagged the bottle negative.The curve did not show signs of growth as the recovered organism produced little or no co2 while in the bottle.The shape of the curve is merely the sample effect.The most likely root cause is the sample did not produce sufficient carbon dioxide to be determined positive by the instrument.It is not an uncommon occurrence for blood culture tests to be negative with another bottle in the set turning positive.The cumitech 1c blood cultures iv and clsi document m47-a principles and procedures for blood cultures, for information regarding recommended number of blood cultures, concluded that two to four blood cultures are necessary to optimize detection of bacteremia and fungemia.A substantial number of bacteremias would be missed if only one blood culture were obtained.An organism would not produce enough co2 for the instrument to flag it positive if: -low number present in inoculum [i.E.Below or at the limit of detection] and more incubation time is needed than the set maximum test time, low sample volume could contribute -presence of inhibitory factors in sample [drugs, immune factors], maybe in addition to low organism count in sample -organism is damaged in some way, maybe by prior drug treatment, sample handling, such that it does not grow like a healthy strain -organism has mutation or gene expression where it just grows slower [i.E.Forms a biofilm, uses a different metabolism].Growth is too slow for clinical algorithm to trigger.-organism already reached and is past log phase growth, numbers of organism present in bottle are too high, there are toxic byproducts, thus do not actively grow anymore [can be seen in delayed entry, or in cases like body fluids where the organism multiplies in the fluid prior to sampling for the bottle] the package insert 410851 bact/alert fa plus states in the section of limitations of the test (1) that fastidious microorganisms may not produce sufficient carbon dioxide to be determined positive.The package insert also alerts the customer in the laboratory procedure (2) that negative bottles may be checked by smear or subculture before being discarded as negative.It is possible that certain rare, fastidious microorganisms will not grow or may grow slowly in the bact/alert fa plus culture bottle growth medium.In addition, on rare occasions, organisms may be encountered that grow in the bact/alert fa plus culture bottle growth medium but do not produce sufficient carbon dioxide to be determined positive.If rare, fastidious organisms requiring specialized media and culture conditions are suspected, alternative methods or extended incubation time should be considered for recovery.Negative bottles may be checked by smear and/or subculture at some point prior to discarding as negative.Organisms are often few in numbers and may appear intermittently in the blood stream; therefore, consecutive blood samples should be collected from each patient.The package insert 410851 bact/alert fa plus states in the section of bottle preparation.Although lower sample volumes can be used, recovery may be improved using a sample volume closer to the recommended 10 ml.In summary, the most probable root cause is sample related.The bottle and instrument functioned as intended.
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