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Cefepime Antibiotic Susceptibility Test by Slow Microbial Growth (Serum/Plasma)

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

This test measures how much of the antibiotic cefepime your body can handle over time, helping determine if your infection will respond to this medication.

Quick summary

["Assists doctors in deciding the best antibiotic dose for your infection."]

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

Key facts at a glance

LOINC
50631-1
Short code
CEFES
Synonyms
Cefepime Islt SlowMyco
Category
chemistry
Sample
serum
Container
Sterile screw-cap container or mycobacterial transport medium container; isolate on solid or liquid mycobacterial medium
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
method-for-slow-growing-mycobacteria
CPT
87186
SNOMED
43798004
Specimen volume
Pure culture isolate of slow-growing mycobacteria on appropriate solid medium (LJ slant or Middlebrook agar) or liquid culture
Stability
Mycobacterial isolates should be tested within 7 days of visible growth. If delayed, subculture to fresh medium and maintain viability. Transport medium specimens stable at 2-8°C for up to 24 hours.
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
72–336 hours
Order
routine

What This Test Measures

Cefepime is a broad-spectrum antibiotic used to treat serious bacterial infections. This test evaluates its concentration in your bloodstream over time, specifically how long it remains effective against bacteria. The slow microbial growth method helps assess susceptibility by observing bacterial response to cefepime levels in your serum or plasma.

Why It’s Done

Your healthcare provider may order this test if you’re prescribed cefepime to treat a bacterial infection, particularly if the infection is severe or resistant to other antibiotics. It helps ensure the antibiotic remains effective in your bloodstream to fight the infection.

How It Works

A sample of your blood (serum or plasma) is collected and tested for cefepime levels. The slow microbial growth method involves monitoring bacterial cultures exposed to cefepime over time to determine the minimum inhibitory concentration (MIC), which indicates the lowest concentration needed to inhibit bacterial growth.

Preparation

No special preparation is needed for this test. Blood is typically drawn in a standard manner, and the sample is processed for analysis.

Reference range

Interpretive categories per CLSI M24 guidelines: Susceptible (S), Intermediate (I), Resistant (R). Breakpoints: Susceptible ≤8 μg/mL, Intermediate 16 μg/mL, Resistant ≥32 μg/mL for MAC; refer to current CLSI document for species-specific breakpoints.N/A

Specimen: serum

No fasting required. Specimen should be collected prior to next dose of antimicrobial therapy when possible. Patient should not be on ongoing topical antiseptics at collection site.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Cefepime MIC (Serum/Plasma)

Frequently asked questions

How does cefepime MIC testing differ from standard antibiotic susceptibility testing?
This test specifically focuses on cefepime’s concentration in your blood over time, providing data on how long the antibiotic remains active. Standard susceptibility testing usually identifies whether bacteria are resistant or sensitive to cefepime, but this method gives additional insight into pharmacokinetics (how the drug behaves in your body).
What does a high or low cefepime MIC mean for my treatment?
A higher MIC suggests the bacteria may require higher doses of cefepime to be effective, while a lower MIC indicates the drug is likely to work well at standard doses. Your doctor will interpret results in the context of your specific infection and overall health.
Can cefepime MIC testing be done on other fluids besides blood?
No, this specific test is performed on serum or plasma samples. However, similar susceptibility testing can sometimes be done on other body fluids (like cerebrospinal fluid) depending on the infection site, but cefepime MIC testing is most commonly done on blood.
  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