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Lower Respiratory Tract Culture (with Antimicrobial Susceptibility Testing)

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

This test checks for bacteria or fungi in samples collected from your lower respiratory tract, such as sputum or bronchoalveolar lavage fluid. It also helps determine if any identified microbes are resistant to certain antibiotics.

Quick summary

["This test helps diagnose infections and guides treatment choices for lung infections."]

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

Key facts at a glance

LOINC
91783-1
Short code
CMV Lower resp Ql Cult
Synonyms
CMV Lower resp Ql Cult
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
organism-specific-culture
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

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms like persistent cough, fever, shortness of breath, or chest pain that suggest a lung infection. It’s also used in patients with weakened immune systems, chronic lung conditions, or those who’ve recently been exposed to certain infections.

Sample Collection

A sample is collected from your respiratory tract, often through sputum induction (by inhaling saline to loosen mucus), bronchoscopy, or other procedures. The sample is then sent to a lab for culture and testing.

What Happens Next

The lab grows the sample in special environments to identify bacteria or fungi. If microbes are found, they are tested for antibiotic resistance patterns. Results typically take 3–14 days, depending on the complexity of the culture.

Possible Results

A negative result means no obvious bacteria or fungi were detected in the sample. A positive result indicates the presence of specific microbes, which may require treatment with targeted antibiotics or antifungals based on susceptibility testing.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Lower Resp Culture

Frequently asked questions

What does a positive result mean?
A positive culture confirms a bacterial or fungal infection in your lower respiratory tract. This helps your doctor choose the most effective treatment, whether it’s antibiotics, antifungals, or other therapies. Resistance patterns can also guide decisions about which medications to avoid.
How long will I need to wait for results?
Results can take anywhere from 3 to 14 days, depending on the complexity of the culture and whether susceptibility testing is needed. Your doctor will discuss the timeline with you before sending the sample.
Can I take antibiotics before getting this test?
No, taking antibiotics before the test may give false-negative results. If you suspect an infection, inform your doctor immediately so they can adjust your treatment plan accordingly.
  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