Evaluation of two rapid phenotypical tests\u2014Alifax rapid AST colistin test and Rapid Polymyxin NP test\u2014for detection of colistin resistance in Enterobacterales

Julija Germ,Tjasa Cerar,Mateja Pirs,Veronika Krizan Hergouth,Katja Seme

doi:10.1007/s10096-021-04182-w

Abstract

Our study evaluates the performance of two rapid phenotypical tests to detect colistin resistance in Enterobacterales: Alifax rapid AST colistin test using the HB&L system and Rapid Polymyxin NP test prepared in-house. A collection of well-characterized 53 colistin-susceptible and 66 colistin-resistantEnterobacterales isolates was used. The results obtained using both rapid tests were compared to the reference broth microdilution. Overall categorical agreement was 81.5% for Alifax test and 98.3% for Rapid Polymyxin NP test. Based on our results, the Rapid Polymyxin NP test is superior to the Alifax test that performed inadequate for Enterobacter spp.

Highlights

Colistin use in clinical practice is mainly restricted to treatment of severe infections caused by multidrug-resistant (MDR) Gram-negative bacilli (GNB) [1]
This study evaluates the performance of two rapid tests that detect colistin resistance in Enterobacterales isolates and compares the results with the reference broth microdilution (BMD)
Among the 66 colistin-resistant isolates, categorical agreement (CA) determined per species/ genus was 100.0% for E. coli, 100.0% for K. pneumoniae, 88.9% for Enterobacter spp., and 100.0% for Citrobacter spp

Summary

Introduction

Colistin use in clinical practice is mainly restricted to treatment of severe infections caused by multidrug-resistant (MDR) Gram-negative bacilli (GNB) [1]. It is rarely included in routine susceptibility panels in medical microbiology laboratories. Colistin susceptibility testing is methodologically challenging due to its inherent properties [1,2,3]. Because colistin susceptibility testing is usually performed on demand when it becomes a treatment option results are delayed for up to 24 h. To reduce the time to results and provide simpler testing, several rapid tests have been developed [5,6,7]

Methods

Results

Conclusion