Evaluation of digital dispense-assisted broth microdilution antimicrobial susceptibility testing for Pseudomonas aeruginosa isolates

Shawn T Clark,David S Guttman,Yvonne C W Yau,Valerie J Waters,Pauline W Wang,David M Hwang,Patrick J Stapleton

doi:10.1038/s41598-021-88423-0

Abstract

Antimicrobial susceptibility testing (AST) is essential for detecting resistance in Pseudomonas aeruginosa and other bacterial pathogens. Here we evaluated the performance of broth microdilution (BMD) panels created using a semi-automated liquid handler, the D300e Digital Dispenser (Tecan Group Ltd., CH) that relies on inkjet printing technology. Microtitre panels (96-well) containing nine twofold dilutions of 12 antimicrobials from five classes (β-lactams, β-lactam/β-lactamase inhibitors, aminoglycosides, fluoroquinolones, polymyxins) were prepared in parallel using the D300e Digital Dispenser and standard methods described by CLSI/ISO. To assess performance, panels were challenged with three well characterized quality control organisms and 100 clinical P. aeruginosa isolates. Traditional agreement and error measures were used for evaluation. Essential (EA) and categorical (CA) agreements were 92.7% and 98.0% respectively for P. aeruginosa isolates with evaluable on-scale results. The majority of minor errors that fell outside acceptable EA parameters (≥ ± 1 dilution, 1.9%) were seen with aztreonam (5%) and ceftazidime (4%), however all antimicrobials displayed acceptable performance in this situation. Differences in MIC were often log2 dilution lower for D300e dispensed panels. Major and very major errors were noted for aztreonam (2.6%) and cefepime (1.7%) respectively. The variable performance of D300e panels suggests that further testing is required to confirm their diagnostic utility for P. aeruginosa.

Highlights

Antimicrobial susceptibility testing (AST) is essential for detecting resistance in Pseudomonas aeruginosa and other bacterial pathogens
Fifteen QC panels created by the D300e Digital Dispenser were compared to traditional reference BMD (rBMD) using the Clinical and Laboratory Standards Institute (CLSI)-recommended E. coli ATCC 25922, E. coli ATCC 35218, and P. aeruginosa ATCC 27853 control strains
The overall EA which included both on- and off-scale measurements was acceptable at 96.5%, variability was noted among the test organisms/antimicrobial combinations (Table 2)

Summary

Introduction

Antimicrobial susceptibility testing (AST) is essential for detecting resistance in Pseudomonas aeruginosa and other bacterial pathogens. We evaluated the performance of broth microdilution (BMD) panels created using a semi-automated liquid handler, the D300e Digital Dispenser (Tecan Group Ltd., CH) that relies on inkjet printing technology. Broth microdilution (BMD) is the preferred method to determine the minimum inhibitory concentrations (MIC) of P. aeruginosa and many other pathogens by AST, as recommended by the Clinical and Laboratory Standards Institute (CLSI), the European Committee on Antimicrobial Susceptibility Testing and the International Organization for S tandardization[2,3]. The objective of this study was to evaluate the performance of P. aeruginosa-focused AST panels created by the D300e Digital Dispenser containing 12 antimicrobials with varying antipseudomonal activity, as compared to reference BMD (rBMD) methods

Objectives

Methods

Results

Conclusion