XPERT MRSA/SA BC (US)

Description of Event or Problem

US CUSTOMER CONTACTED CEPHEID TO REPORT A QUESTIONABLE NEGATIVE RESULT ON PERT MRSA/SA BC ASSAY. THE CUSTOMER REPORTED STAPHYLOCOCCUS AUREUS WAS IDENTIFIED BY MALDI TOF, BUT INITIAL AND REPEAT EXPERT MRSA/SA BC TESTS WERE SA NEGATIVE. THE BLOOD CULTURE WAS COLLECTED ON (B)(6) 2026, FLAGGED POSITIVE ON (B)(6) 2026 AT 03:27, AND TESTING WAS PERFORMED FROM THE AEROBIC BD BACTEC PLUS BOTTLE. THE LABORATORY FOLLOWED IFU, PERFORMED GRAM STAIN (GRAM POSITIVE COCCI IN CLUSTERS OBSERVED), AND USED ROUTINE CULTURE PLATES (BAP, CHOC, MAC). NO MIXED CULTURE WAS NOTED. SUSCEPTIBILITY TESTING (MICROSCAN WALKAWAY) WAS COMPLETED (OXACILLIN SUSCEPTIBLE) AND REPORTED TO THE PHYSICIAN. REPEAT EXPERT MRSA/SA BC TESTING WAS PERFORMED BECAUSE ITS RESULTS DID NOT CORRELATE WITH MALDI TOF IDENTIFICATION. THE SPECIMEN FOR REPEAT TESTING WAS STORED IN NON CO2 INCUBATION FOR 24 HOURS. THE PATIENT WAS 89 YEARS OLD WITH DIABETES AND VASCULAR DISEASE; IMMUNOCOMPROMISED STATUS WAS UNKNOWN. THE PATIENT WAS HOSPITALIZED AND HAS SINCE EXPIRED, BUT NO ADVERSE OUTCOME WAS ATTRIBUTED TO THE TEST DISCREPANCY. NO PATIENT HARM WAS REPORTED, AND THE CUSTOMER CONFIRMED NO ADVERSE OUTCOME ATTRIBUTABLE TO THE DISCREPANCY.

Additional Manufacturer Narrative

TEST REPORTS AND CASE DETAILS WERE REVIEWED. IN REGARD TO THE TESTING DETAILS, THE CHANGE IN CT FOR 3RD TEST, AFTER 24-HOUR INCUBATION AT ROOM TEMP IS EXPECTED AND COULD BE DUE TO GROWTH OF BACTERIA DURING STORAGE. THE DISCREPANCY BETWEEN XPERT MRSA/SA BC AND THE OTHER IDENTIFICATION METHODS EMPLOYED SUGGESTS MUTATIONS OR DELETIONS IN THE SPA GENE WHICH IS THE TARGET USED IN THE XPERT MRSA/SA BC TEST TO IDENTIFY THE PRESENCE OF S. AUREUS. A PHONE CALL WITH CUSTOMER WAS MADE ON 23-JAN-2026 AND THE CUSTOMER INFORMED THAT THE PATIENT CAME INTO THE FACILITY WITH ACUTE ISCHEMIC STROKE AND WAS HOSPITALIZED. CUSTOMER CONFIRMED ONCE AGAIN THAT DEATH WAS NOT DUE TO DISCREPANT RESULT FROM XPERT MRSA/SA BC. THIS CASE IS A FALSE NEGATIVE RESULT WITH XPERT MRSA/SA BC DUE TO A RARE MUTATION IN THE SPA GENE.

Additional Manufacturer Narrative

RESPONSE TO FDA REQUEST FOR ADDITIONAL INFORMATION. PLEASE SEE THE UPDATED INFORMATION BELOW OBTAINED FROM THE CUSTOMER AND PROVIDED TO THE FDA ON 19-FEB-2026. THE PATIENT DID NOT EXPIRE AT THE CUSTOMER'S FACILITY, THE CAUSE OF DEATH IS UNKNOWN. THE PATIENT, AN 89-YEAR-OLD MALE WITH A HISTORY OF CORONARY ARTERY DISEASE STATUS POST CABG, PRIOR CEREBROVASCULAR ACCIDENT, ATRIAL FIBRILLATION, AND HEART FAILURE WITH REDUCED EJECTION FRACTION (35-40%), WAS ADMITTED ON (B)(6) 2026 FOR ALTERED MENTAL STATUS. IMAGING ON ADMISSION DEMONSTRATED EVOLVING CEREBELLAR STROKES. THE PATIENT REMAINED ON ELIQUIS AND ASPIRIN DURING THE HOSPITALIZATION. NEUROLOGY AND CARDIOLOGY WERE CONSULTED AND COMPLETED THEIR EVALUATIONS. DURING THE HOSPITAL COURSE, THE PATIENT DEVELOPED ASPIRATION PNEUMONIA WITH ASSOCIATED SEPSIS. EMPIRIC ANTIMICROBIAL THERAPY WITH UNASYN WAS INITIATED ON (B)(6) 2026 AT 06:49 AND CONTINUED THROUGH (B)(6) 2026, WITH THE FINAL DOSE ADMINISTERED AT 21:15 ON (B)(6) 2026. AZITHROMYCIN WAS ALSO PROVIDED AS PART OF THE TREATMENT PLAN PER PROVIDER DOCUMENTATION. A 2-GRAM DOSE OF ANCEF WAS PULLED FROM THE GI LAB ON (B)(6) 2026 AT 08:12. ADDITIONAL THERAPEUTIC ANCEF WAS ADMINISTERED FROM (B)(6) 2026 TO (B)(6) 2026 FOR MSSA COVERAGE, WITH THE FIRST DOSE GIVEN AT 10:30 ON 0(B)(6) 2026 AND THE LAST DOSE AT 11:40 ON (B)(6) 2026. ANCEF WAS DISCONTINUED AT DISCHARGE. DURING THE ADMISSION, THE PATIENT DEVELOPED FREE WATER DEFICIT, HYPERNATREMIA, AND ACUTE KIDNEY INJURY. MANAGEMENT INCLUDED IV FLUIDS AND INCREASED PEG TUBE FEEDINGS. HYPERNATREMIA IMPROVED TO 146 MEQ/L ON (B)(6) 2026. DURING A SPEECH THERAPY REASSESSMENT, THE PATIENT WAS OBSERVED TO HAVE BLEEDING AT THE BACK OF THE MOUTH AND VERY DRY MUCOUS MEMBRANES. ON REASSESSMENT THE FOLLOWING DAY. THE BLEEDING HAD RESOLVED AFTER ORAL CARE. THE PATIENT WAS DISCHARGED ON (B)(6) 2026. THE PATIENT SUBSEQUENTLY EXPIRED ON (B)(6) 2026. NO FURTHER CLINICAL DETAILS REGARDING CIRCUMSTANCES OF DEATH WERE PROVIDED.