Multicenter Clinical Evaluation of ETEST Plazomicin (PLZ) for Susceptibility Testing of Enterobacterales
Related Experiment Video
Updated: Oct 13, 2025
Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance
Published on: May 2, 2018
Laurine S Blanchard1, Alex Van Belkum2, Dominique Dechaume2
1bioMérieux SA, Marcy l'Etoile, France.
Abstract:
Plazomicin (PLZ), brand name ZEMDRI (Cipla Therapeutics), is a novel aminoglycoside antibiotic approved by the U.S. Food and Drug Administration (FDA) for treatment of complicated urinary tract infections including pyelonephritis. ETEST® is a gradient diffusion method that represents an alternative to the more laborious broth micro-dilution (BMD) method for performing antimicrobial susceptibility testing (AST). A multi-center evaluation of the performance of the new ETEST PLZ (bioMérieux) was conducted in comparison with BMD following FDA and International Standards Organization (ISO) recommendations using FDA-defined breakpoints. Clinical isolates of Enterobacterales (n = 598) were included. Fifty-three isolates were resistant to PLZ according to BMD. Overall, the ETEST PLZ demonstrated 99.0% essential agreement (EA), 92.8% category agreement (CA), 1.9% very major errors (VME), 0% major errors (ME), and 7.0% minor errors (mE) with both clinical and challenge isolates of Enterobacterales. The VME was found for a single Serratia marcescens strain. Individual species demonstrated EA rates ≥ 90%. In conclusion, we report that ETEST PLZ represents an accurate tool for performing PLZ AST of Enterobacterales.
Insights
The ETEST Plazomicin test accurately determines susceptibility for Enterobacterales, offering a reliable alternative to traditional methods for this novel antibiotic.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Plazomicin (PLZ), marketed as ZEMDRI, is a novel aminoglycoside antibiotic approved for complicated urinary tract infections.
- Antimicrobial susceptibility testing (AST) is crucial for guiding treatment, with broth micro-dilution (BMD) being a standard but labor-intensive method.
- Gradient diffusion methods, like ETEST®, offer a potentially more convenient alternative for AST.
Purpose of the Study:
- To evaluate the performance of the novel ETEST Plazomicin (PLZ) assay.
- To compare ETEST PLZ results against the gold standard broth micro-dilution (BMD) method for Enterobacterales.
- To assess ETEST PLZ accuracy according to FDA and ISO guidelines using established breakpoints.
Main Methods:
- A multi-center study evaluated the ETEST PLZ against BMD for AST.
- 598 clinical isolates of Enterobacterales were tested, including 53 resistant to PLZ by BMD.
- Performance metrics included essential agreement (EA), category agreement (CA), and error rates (VME, ME, mE).
Main Results:
- ETEST PLZ demonstrated high overall essential agreement (99.0%) and category agreement (92.8%) with BMD.
- The test showed a low rate of very major errors (1.9%) and no major errors (0%).
- Individual species exhibited essential agreement rates of 90% or higher, with a single very major error in Serratia marcescens.
Conclusions:
- The ETEST Plazomicin assay is an accurate tool for performing antimicrobial susceptibility testing of Enterobacterales.
- ETEST PLZ provides a reliable and potentially more efficient alternative to BMD for guiding plazomicin therapy.
- The findings support the clinical utility of ETEST PLZ for routine AST in healthcare settings.
