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The KeyPath™ MRSA/MSSA Blood Culture Test – BT is a qualitative in vitro diagnostic test for the timely identification of Staphylococcus aureus (S. aureus) and determination of methicillin susceptibility (MSSA) or methicillin resistance (MRSA) directly from positive blood cultures. The Test uses bacteriophage amplification to identify the presence of S. aureus and assess the phenotypic response of the target organism to cefoxitin, an indicator of oxacillin (a methicillin analog) resistance. The assay is performed directly on positive blood culture specimens that are determined as Gram Positive Cocci in singles (GPC) or as Gram Positive Cocci in Clusters (GPCC) by Gram stain. The KeyPath™ MRSA/MSSA Blood Culture Test - BT is performed directly on positive blood culture specimens from BD BACTEC™ blood culture bottles (Plus Aerobic/F, Plus Anaerobic/F, Standard/10 Aerobic/F and Standard Anaerobic/F). The Test is indicated for use in conjunction with other laboratory and clinical data available to the physician as an aid in the detection of MRSA/MSSA from positive blood cultures. Subculturing of positive blood cultures is necessary for additional susceptibility test determinations, differentiation of mixed growth and for epidemiological typing.

The KevPath™ MRSA/MSSA Blood Culture Test - BT (KevPath™ Test) is a bacteriophage amplification-enabled immunoasay to identify Staphylococcus aureus and determine its resistance or susceptibility to cefoxitin from positive blood cultures, which have been determined to have Gram Positive Cocci in singles (GPC) or Gram Positive Cocci in Clusters (GPCC) by Gram stain. This method utilizes the specificity of bacteriophage/bacteria interactions and their natural amplification processes to produce a surrogate signal. In the presence of S. aureus, bacteriophage will replicate, increasing to a detectable concentration. In the absence of S. aureus or the presence of bacteria other than S. aureus, the KevPath™ Test bacteriophage do not replicate and remain undetectable. In addition, susceptible strains of S. aureus do not grow in the presence of cefoxitin and therefore do not support bacteriophage amplification, while resistant strains will grow and support bacteriophage amplification. To perform the KeyPath™ Test, a sample of the positive blood culture is added to each of the two provided reaction tubes, each comprised of KeyPath™ Test bacteriophage and proprietary reagents that enhance the growth of S. aureus and suppress other organisms. One Reaction Tube (Blue) is used for S. aureus identification. The second Reaction Tube (Red) is used for resistance/susceptibility testing. Following incubation, a small amount of the sample from each Tube is pipetted onto corresponding sample wells on the Detector. If the specimen contains S. aureus a pink-to-dark red/ purple Test Line (T) will appear in the Blue ID Window of the Detector. If the sample is positive for S. aureus, Resistance/Susceptibility is then determined by reading the Red RS Window. Resistance (MRSA) is determined by the development of a visible pink-to-dark red/purple line at the Test Line (T) in the Red RS Window, while Susceptibility (MSSA) is determined by the absence of a visible colored line at the Test Line (T) in the Red RS Window.

The KeyPath™ MRSA/MSSA Blood Culture Test - BT is a qualitative in vitro diagnostic test for the timely identification of Staphylococcus aureus (S. aureus) and determination of methicillin susceptibility (MSSA) or methicillin resistance (MRSA) directly from positive blood cultures. The Test uses bacteriophage amplification to identify the presence of S. aureus and assess the phenotypic response of the target organism to cefoxitin, an indicator of oxacillin (a methicillin analog) resistance. The assay is performed directly on positive blood culture specimens that are determined as Gram Positive Cocci in singles (GPC) or as Gram Positive Cocci in Clusters (GPCC) by Gram stain. The KeyPath™ MRSA/MSSA Blood Culture Test - BT is performed directly on positive blood culture specimens from BD BACTEC™ blood culture bottles (Plus Aerobic/F and Plus Anaerobic/F). The Test is indicated for use in conjunction with other laboratory and clinical data available to the physician as an aid in the detection of MRSA/MSSA from positive blood cultures. Subculturing of positive blood cultures is necessary for additional susceptibility test determinations, differentiation of mixed growth and for epidemiological typing.

The KeyPath™ MRSA/MSSA Blood Culture Test – BT uses lytic bacteriophage, specific for Staphylococcus aureus, as an amplification technology for detection of S. aureus and determination of methicillin resistance or susceptibility in positive blood cultures. To detect S. aureus (ID Reaction Tube), the bacteriophage infect the S. aureus (if present), replicate within the host (culminating in bacterial lysis) and over the incubation period, produce several cvcles of bacteriophage amplification. In a separate Reaction Tube (RS), the Test uses cefoxitin (an oxacillin and methicillin analog) which inhibits bacteriophage amplification for susceptible organisms (MSSA) and fails to inhibit bacteriophage amplification when the organism is resistant to methicillin (MRSA). The Test then uses a self-performing immunoassay (Detector) to detect the increase in concentration of bacteriophage using antibodies specific to the Test bacteriophage, and calibrated such that at above a threshold concentration, it produces a visible signal.