Gram-Positive Blood Cultures*
For in vitro Diagnostic Use
| Verigene® Gram Positive Blood Culture Tests | ||||
|---|---|---|---|---|
| Available Test Panels | ||||
| BC-S*: US/FDA-Cleared | BC-GP: Outside US | |||
| Targets | Genus | Staphylococcus spp. |
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| Streptococcus spp. |
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| Micrococcus spp. |
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| Listeria spp. |
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| Species | Staphylococcus aureus |
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| Staphylococcus epidermidis |
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| Staphylococcus lugdunensis |
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| Streptococcus pneumoniae |
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| Streptococcus anginosus Group |
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| Streptococcus agalactiae |
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| Streptococcus pyogenes |
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| Enterococcus faecalis |
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| Enterococcus faecium |
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| Resistance | mecA |
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| vanA |
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| vanB |
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| Automation | Sample-to-Result | |||
| Instrumentation | Verigene Reader and Processor SP | |||
| Workflow | Random Access | |||
| Sample Type | Positive Blood Culture Bottle† | |||
| Hands-On Time | <5 minutes | |||
| Run Time | <2.5 hours | |||
*Additional targets pending FDA review.
†Validated for use with two manufacturers’ specific aerobic blood culture bottles; see BC-S package insert for details.
Background
In 2009, septicemia was associated with more than 800,000 hospitalizations in the United States and was the most expensive cause of hospitalization.1 Septicemia occurs when a pathogenic microorganism, usually a bacterium or a fungus, enters the bloodstream and causes an inflammatory immune response. Because bloodstream infections and septicemia are pervasive problems associated with high mortality rates, timely delivery of appropriate treatment is essential.
Bloodstream infections with gram-positive bacteria are often complicated by antimicrobial resistance. The inability to rapidly identify resistant strains of pathogenic bacteria has led to antimicrobial use that is often ineffectual, wasteful, or bears risk of proliferating resistant strains. Rapid identification of both organism and resistance is essential to implementing efficient and appropriate therapy.2
Gram-positive bacteria are also a common source of contamination during blood draws. Contaminant species are frequently responsible for false-positive blood cultures that lead to inappropriate antimicrobial use.3 Patients with contaminated blood culture bottles are often presumptively treated for bloodstream infections for several days until the organism can be identified as a contaminant using conventional biochemical methods. Due to the large burden of infections and contaminants due to gram-positive bacteria, rapid identification of bacteria isolated from blood cultures is a primary healthcare concern.
The Verigene Gram-Positive Blood Culture (BC-GP) Test is a multiplexed, automated nucleic acid test for the identification of genus, species, and genetic resistance determinants for a broad panel of the most common gram-positive blood culture isolates. While conventional microbiological methods may require 2-4 days to produce bacterial identification and resistance results, the Verigene BC-GP test provides results within 2.5 hours of blood culture positivity. The Verigene System’s unique instrumentation allows for true random access test processing, enabling 24/7 on-demand testing directly from positive blood culture bottles with less than 5 minutes of user hands-on time per test.
References
- Elixhauser A, Friedman B, Stranges E. 2011. Septicemia in US Hospitals, 2009. HCUP Statistical Brief #122. Agency for Healthcare Research and Quality.
- Sahm DF et al, 1997. Rapid Characterization Schemes for Surveillance Isolates of Vancomycin-Resistant Enterococci. JCM 8:2026-2030
- von Eiff C, Herrmann M, Peters G. 1995. Antimicrobial susceptibilities of Stomatococcus mucilaginosus and of Micrococcus spp. Antimicrob Ag Chemo. 39:268-270.
Workflow
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STEP 1
Load Test Cartridge, test consumables, and sample into Processor SP
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STEP 2
Automated sample preparation and test processing on Processor SP
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STEP 3
Place slide from Test Cartridge in Verigene Reader for results
Literature Cited
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"Evaluation of the Microarray‐Based Sample‐to‐Result Verigene BC‐GP Assay for Rapid Detection of Gram‐Positive Bacteria and Resistance Determinants Directly from Positive Blood Cultures"18 September 2011Full dataAbstract
Background: Bacteremia and sepsis result in high morbidity and mortality. A majority of positive blood cultures are due to gram‐ positive bacteria including Staphyloccocus, Enterococcus, Streptococcus, and Micrococcus. Some of these organisms are associated with serious infection, while others are skin flora associated with lines or improperly collected specimens. Early identification of the organism and appropriate antibiotic treatment is critical to management of the infection and improving patient outcome.
Methods: Sixty positive blood cultures containing gram‐positive bacteria were analyzed using the Verigene Gram Positive Blood Culture (BC‐GP) Assay (Nanosphere, Northbrook, IL). Testing of cultures was done within 8h of positivity. The BC‐GP detects 13 bacterial targets including Staphylococcus, Streptococcus, Enterococcus, Micrococcus and Listeria species. The resistance determinants mecA (oxacillin) and vanA/B (vancomycin) are also detected.
Results: Three cultures contained organisms not on the BC‐GP panel (Bacillus, Lactobacillus), and were resulted as “Not Detected”. Compared to biochemical identification, 55 of 57 positive blood cultures were concordant with BC‐GP results. One culture contained viridans group Streptococci by biochemical identification, which was discordant with the BC‐GP result (S. pneumoniae). In 4 of 5 cultures containing two organisms the BC‐GP correctly identified both organisms; in one culture the BC‐GP identified 1 of 2 organisms present. This translates to a combined sensitivity of 98.4%. The BC‐GP predicted oxacillin resistance in 34 Staphylococcus spp. (18 mecA +) and vancomycin resistance in 10 Enterococcus spp. (6 vanA +) for 100% sensitivity and specificity.
Conclusions: The BC‐GP assay identifies 13 gram‐positive targets and 2 resistance markers directly from positive blood cultures. The BC‐GP requires only 350μl of specimen and results are available within 2.5 hours of blood culture positivity.
