Macrolide Resistance Detection in *Streptococcus pneumoniae* (Pneumococcal) by Measuring Methylation of mecA Gene
This test checks whether certain bacteria, including *Streptococcus pneumoniae*, may be resistant to macrolide antibiotics like azithromycin or clarithromycin. Resistance can affect how well these medications work to treat infections.
["Determining antibiotic resistance helps doctors choose the best treatment for bacterial infections."]
Key facts at a glance
- LOINC
- 105812-2
- Short code
- MECACt
- Synonyms
- Bac macrolide res mecA Ct Bld +
- Category
- chemistry
- Sample
- whole-blood
- Container
- Positive blood culture bottle (aerobic or anaerobic) submitted in original culture bottle
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- probe-amp-tar
- CPT
- 87641
- SNOMED
- 115329001
- Specimen volume
- 3-10 mL positive blood culture broth transferred to sterile tube or tested directly from blood culture bottle
- Stability
- Test should be performed within 24 hours of blood culture positivity signal; if delay expected, refrigerate at 2-8°C for up to 24 hours
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 1–4 hours
- Order
- routine
Why This Test Might Be Ordered
Your doctor may order this test if you have symptoms of pneumonia, sinusitis, or other infections caused by *Streptococcus pneumoniae*. It’s also used in settings where macrolide resistance is known to be common, such as certain geographic regions or populations.
What the Test Measures
The test detects genetic changes (specifically methylation of the *mecA* gene) that can make *Streptococcus pneumoniae* resistant to macrolide antibiotics. This is done through a molecular method that identifies these genetic markers in a sample of your blood or other bodily fluid.
Sample Collection and Preparation
A blood sample or other fluid (like cerebrospinal fluid in some cases) is collected and sent to a lab. The lab uses advanced techniques to analyze the genetic material (DNA) of the bacteria present in your sample.
What the Results Mean
If the test finds the methylation markers, it suggests that the bacteria may be resistant to macrolides. However, this does not confirm infection with resistant bacteria alone—additional testing may be needed to identify the exact bacteria and its resistance profile.
Reference range
Reported as cycle threshold (Ct) value; mecA gene detected or not detected in positive blood cultureN/A
No special patient preparation required; specimen is collected from positive blood culture bottle flagged by continuous monitoring blood culture system
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Macrolide Resistance Screening (Pneumococcal)
Frequently asked questions
What does a positive result mean?
How soon will I get my results?
Can I take antibiotics before the test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
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