Related Experiment Video
Updated: Dec 14, 2025
Population and Single-Cell Analysis of Antibiotic Persistence in Escherichia coli
Published on: March 24, 2023
Polymyxin B broth disk elution: a feasible and accurate methodology to determine polymyxin B susceptibility in
Naiany C Cielo1, Tanise Belmonte1, Otávio H F Raro2
1Department of Analysis, Faculty of Pharmacy, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
Abstract:
Determination of polymyxins susceptibility by clinical laboratories is a nightmare, mainly because of physicochemical properties of the drug. Elution tests have already been proposed for colistin, but not for polymyxin B. We aimed to evaluate accuracy of Polymyxin B broth disk elution (PBDE) to determine the susceptibility to this drug. We evaluated 196 Enterobacterales (45.9% polymyxin B-resistant). PBDE was done in 15-mL cation-adjusted Mueller-Hinton broth where one polymyxin B disk (300 U) was eluted (2 μg/mL). BMD was performed as reference method. Categorical Agreement (CA), Major Error (ME) and Very Major Error (VME) were 99.5%, 0% and 1.11% (one false-negative K. pneumoniae MIC 4 μg/mL), respectively. As some institutions preferably use polymyxin B over colistin and in some countries colistin are not commercially available, to specifically evaluate polymyxin B is important. PBDE proved to be a cheap and easy to perform methodology to evaluate susceptibility to polymyxin B among Enterobacterales.
Insights
Determining polymyxin B susceptibility is challenging. The Polymyxin B broth disk elution (PBDE) method offers a cheap, easy, and accurate way to test Enterobacterales, with 99.5% categorical agreement.
Area of Science:
- Microbiology
- Clinical Diagnostics
- Antimicrobial Resistance
Background:
- Accurate determination of polymyxin susceptibility is crucial for clinical laboratories but is often complicated by the drug's physicochemical properties.
- While elution tests exist for colistin, a reliable method for polymyxin B susceptibility testing is lacking.
- Polymyxin B is an important antibiotic, especially in regions where colistin is unavailable or when preferred over colistin.
Purpose of the Study:
- To evaluate the accuracy of the Polymyxin B broth disk elution (PBDE) method for determining polymyxin B susceptibility in Enterobacterales.
- To compare the PBDE method against the gold standard broth microdilution (BMD) method.
- To establish PBDE as a viable alternative for routine clinical susceptibility testing.
Main Methods:
- A total of 196 Enterobacterales isolates were tested.
- Polymyxin B susceptibility was determined using the Polymyxin B broth disk elution (PBDE) method in cation-adjusted Mueller-Hinton broth with a polymyxin B disk (300 U) eluted to a final concentration of 2 μg/mL.
- Broth microdilution (BMD) was performed as the reference method for comparison.
Main Results:
- The PBDE method demonstrated high accuracy, achieving 99.5% categorical agreement (CA) with the BMD reference method.
- No Major Errors (ME) were observed, indicating no instances of resistant isolates being reported as susceptible.
- A Very Major Error (VME) rate of 1.11% was recorded, attributed to one false-negative result for a Klebsiella pneumoniae isolate with a minimum inhibitory concentration (MIC) of 4 μg/mL.
Conclusions:
- The Polymyxin B broth disk elution (PBDE) method is a highly accurate and reliable technique for assessing polymyxin B susceptibility in Enterobacterales.
- PBDE is a cost-effective and user-friendly alternative to traditional methods, suitable for clinical laboratories.
- This method addresses the need for specific polymyxin B susceptibility testing, particularly where colistin is not readily available or preferred.
More Related Videos
08:58Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
Published on: March 3, 2023
07:58Laboratory Techniques Used to Maintain and Differentiate Biotypes of Vibrio cholerae Clinical and Environmental Isolates
Published on: May 30, 2017