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Published on: July 9, 2012
Rapid Detection of Polymyxin-Resistant Enterobacteriaceae from Blood Cultures
Aurélie Jayol1, Véronique Dubois2, Laurent Poirel3
1Emerging Antibiotic Resistance Unit, Medical and Molecular Microbiology, Department of Medicine, University of Fribourg, Fribourg, Switzerland INSERM European Unit (LEA Paris, France), University of Fribourg, Fribourg, Switzerland CNRS UMR5234, University of Bordeaux, Bordeaux, France.
Abstract:
Enterobacterial strains resistant to polymyxins are being increasingly reported worldwide. The conventional methods for detection of colistin-resistant isolates such as broth microdilution remain time-consuming (24 to 48 h), and methods such as disc diffusion and Etest are not reliable. Recently, the rapid polymyxin NP test was developed for rapid identification of polymyxin-resistant Enterobacteriaceae This test is based on the detection of glucose metabolism related to bacterial growth in the presence of a defined concentration of colistin (or polymyxin B). The formation of acid metabolites is evidenced by a color change of a pH indicator (red phenol) in less than 2 h. In this study, the polymyxin NP test was evaluated for detection of colistin-resistant Enterobacteriaceae directly from blood cultures. The test was performed with 73 blood culture sets (either spiked or clinical blood cultures) with various enterobacterial species. The test exhibited excellent discrimination between polymyxin-resistant and polymyxin-susceptible enterobacterial isolates, and results are obtained from blood cultures within 4 h. It is easy to perform and requires neither subculture nor a centrifugation step. This test is rapid, specific, and sensitive and allows early identification of polymyxin-resistant Enterobacteriaceae directly from blood cultures.
Insights
The rapid polymyxin NP test accurately identifies polymyxin-resistant Enterobacteriaceae directly from blood cultures within 4 hours. This method offers a faster and more reliable alternative to conventional techniques for detecting antimicrobial resistance.
Area of Science:
- Clinical microbiology
- Antimicrobial resistance
- Infectious diseases
Background:
- Increasing global reports of polymyxin-resistant Enterobacteriaceae necessitate rapid detection methods.
- Conventional methods like broth microdilution are time-consuming (24-48h), while disc diffusion and Etest lack reliability.
- Early identification of resistance is crucial for effective patient management and infection control.
Purpose of the Study:
- To evaluate the performance of the rapid polymyxin NP test for detecting colistin-resistant Enterobacteriaceae directly from blood cultures.
- To assess the test's speed, accuracy, and ease of use compared to existing methods.
Main Methods:
- The polymyxin NP test was performed on 73 blood culture sets (spiked and clinical) containing various Enterobacteriaceae species.
- The test detects glucose metabolism and acid production in the presence of colistin, indicated by a color change.
- Results were obtained within 4 hours, without requiring subculture or centrifugation.
Main Results:
- The polymyxin NP test demonstrated excellent discrimination between polymyxin-resistant and polymyxin-susceptible Enterobacteriaceae isolates.
- The test provided accurate results directly from blood cultures in under 4 hours.
- The procedure was simple to perform, requiring no additional steps like subculturing or centrifugation.
Conclusions:
- The rapid polymyxin NP test is a fast, specific, and sensitive method for early identification of polymyxin-resistant Enterobacteriaceae.
- This test offers a significant advantage for clinical laboratories managing bloodstream infections caused by resistant Enterobacteriaceae.
- Its direct application to blood cultures streamlines the diagnostic process, enabling quicker therapeutic decisions.
