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Beta-lactamase production screening in *Escherichia coli* (serum/plasma)

Published: August 9, 2026Updated: August 16, 2026

This test checks if your blood contains bacteria that produce beta-lactamases, enzymes that can break down certain antibiotics like penicillin and cephalosporins. It helps doctors determine if your infection may require different treatment.

Quick summary

["Helps identify infections resistant to common antibiotics."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
85844-9
Short code
ESBL blaCTX-M2 Grp gene Islt/Spm Ql
Synonyms
ESBL blaCTX-M2 Grp gene Islt/Spm Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What This Test Measures

Beta-lactamases are enzymes produced by certain bacteria, including *Escherichia coli*, that can degrade beta-lactam antibiotics. This test detects the presence of these enzymes in your blood to see if they are breaking down antibiotics. If positive, it suggests the bacteria may be resistant to these drugs.

Why It Matters in Your Care

If your doctor suspects an infection caused by *E. coli* or other bacteria, this test helps guide antibiotic choices. Knowing if beta-lactamases are present ensures you receive the most effective treatment to fight your infection.

How the Test Works

The test uses a method called **immunoassay** (likely clia or fia) to detect beta-lactamase activity in your serum or plasma. A positive result means the bacteria may be resistant to certain antibiotics, and your doctor will adjust your treatment plan accordingly.

What to Expect Before the Test

No special preparation is needed. You may have a blood draw, similar to other routine blood tests. If you’re on antibiotics, let your doctor know—this may affect results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

ESBL Screen (Serum/Plasma)

Frequently asked questions

Why was this test ordered?
Your doctor may have ordered this test if you have a suspected bacterial infection, especially if symptoms like fever, pain, or signs of infection persist despite antibiotic treatment. It helps identify infections resistant to common antibiotics like ampicillin, ceftriaxone, or cefotaxime.
What does a positive result mean?
A positive result suggests your infection may involve bacteria producing beta-lactamases, meaning they could be resistant to certain antibiotics. Your doctor will work with you to choose a different antibiotic that works better against these bacteria.
Can I take antibiotics before this test?
If you’re already taking antibiotics, inform your doctor before the test. Some antibiotics may interfere with the test results, so they may adjust your treatment plan based on the findings.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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