Understanding Your Medical Test: A Patient's Guide to Testing, Results, and What They Mean for Your Health
A molecular test that detects genetic mutations in the gyrB gene to identify bacterial resistance to quinolone antibiotics.
{"Detects genetic changes (mutations) in bacteria that cause antibiotic resistance","Helps doctors choose the right antibiotic treatment","Uses a blood sample to analyze bacterial DNA","Results guide treatment decisions for bacterial infections","Particularly important for severe or hard-to-treat infections"}
Key facts at a glance
- LOINC
- 101576-7
- Short code
- GYRB-RES
- Synonyms
- Bacterial gyrB drug res mut Islt/Spm
- Category
- chemistry
- Sample
- serum
- Container
- Sterile, leak-proof primary container; appropriate transport medium (e.g., Amies or Stuart transport medium) for bacterial isolates. For serum specimens, use serum separator tube (SST) or plain red-top tube.
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- molgen
- CPT
- 87153
- SNOMED
- 434871000124102
- Specimen volume
- Minimum 1 mL serum for serum-based testing; for bacterial isolates, a pure culture on appropriate solid medium or 0.5-1 mL of broth culture is sufficient for DNA extraction.
- Stability
- Serum: stable at 2-8°C for 7 days; frozen at -20°C or below for up to 30 days for DNA-based assays. Bacterial isolates: maintain at 2-8°C and process within 48-72 hours; freeze at -70°C for long-term storage. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 48–168 hours
- Order
- routine
What is this test and why has my doctor recommended it?
The Bacterial gyrB Gene Drug Resistance Mutation test is a molecular diagnostic test that detects specific genetic changes (mutations) in the gyrB gene of bacteria. The gyrB gene encodes DNA gyrase subunit B, which is the target site for quinolone antibiotics (such as ciprofloxacin, levofloxacin, and moxifloxacin). When bacteria develop mutations in this gene, they can become resistant to these antibiotics, making infections harder to treat.
How is this test performed and what can I expect during the procedure?
A blood sample (serum) is collected from the patient. Laboratory technicians then use molecular techniques, such as polymerase chain reaction (PCR) and DNA sequencing, to analyze the gyrB gene and identify specific mutations associated with antibiotic resistance. This test can detect whether the bacteria causing the infection have genetic changes that make them resistant to quinolone antibiotics.
Why is this test important for my health and ongoing medical care?
Antibiotic resistance is a growing global health concern. Traditional antibiotic sensitivity tests can take days to complete, and some bacteria may be resistant to certain antibiotics even before treatment begins. This molecular test provides rapid and accurate information about genetic resistance, allowing doctors to avoid prescribing ineffective antibiotics and start appropriate treatment sooner. This can improve patient outcomes and help preserve the effectiveness of existing antibiotics.
What do the results mean and how will they help guide my treatment?
If mutations are detected in the gyrB gene, it indicates that the bacteria causing the infection are likely resistant to quinolone antibiotics. The doctor will then select alternative antibiotics that are still effective against the infection. If no mutations are detected, the bacteria should still be sensitive to quinolone antibiotics, though final treatment decisions may also consider other factors and test results.
Reference range
No gyrB resistance mutations detected (wild-type sequence); Reportable mutations include amino acid substitutions such as Asp426Asn, Asp426Val, Arg447His, Arg447Leu, Ser464Tyr, and Glu466Asp associated with fluoroquinolone resistance. Interpretation provided in conjunction with phenotypic susceptibility testing when available.N/A
No special patient preparation required. Specimen collection should occur prior to initiation of antimicrobial therapy when clinically feasible to avoid suppression of bacterial load. Inform the laboratory of current or recent antibiotic use, as this may influence bacterial recovery and mutation detection.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The gyrB gene mutation test is clinically significant for several reasons: (1) It provides rapid detection of antibiotic resistance, allowing for earlier appropriate treatment; (2) It helps guide antibiotic selection for quinolone drugs, reducing trial-and-error prescribing; (3) It is particularly valuable for severe infections such as bloodstream infections, pneumonia, and urinary tract infections where effective antibiotics need to be started quickly; (4) It supports antimicrobial stewardship efforts by promoting appropriate antibiotic use and helping to combat the growing problem of antibiotic resistance.
Frequently asked questions
Does this test tell me which antibiotic to take?
How long does it take to get results?
Do I need to fast before this test?
Is this test painful?
Can the test detect all types of antibiotic resistance?
Sources
- 1
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- 3
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy