Performance of the Vitek 2, Sensititre, and Etest antimicrobial susceptibility testing systems for isolates of Burkholderia cepacia complex

TL;DR

This study compares three antimicrobial susceptibility testing methods for Burkholderia cepacia complex, finding that Sensititre performs best but still has significant errors.

Contribution

The study evaluates three commercial AST systems for BCC, providing new comparative data on their reliability and performance.

Findings

Sensititre showed the highest Essential and Categorical agreements but still had multiple Very Major Errors.

Vitek 2 had the lowest agreement rates, particularly for ceftazidime and meropenem.

All methods showed lower minimum inhibitory concentrations compared to reference methods.

Abstract

Burkholderia cepacia complex (BCC) is a highly antimicrobial-resistant bacteria that frequently colonizes patients with cystic fibrosis. Previous studies have demonstrated inconsistent performance and questionable reliability of disk diffusion, agar dilution, gradient diffusion strip, and Microscan methods. This study evaluated the performance of the Biomerieux Vitek 2, Thermo Scientific Sensititre broth microdilution, and Etest methods for susceptibility testing of BCC organisms in comparison to a previously characterized isolate set. Of the three methods tested, Sensititre had the highest Essential and Categorical agreements (EA and CA, respectively) , though it still produced multiple Very Major Errors (VME). Vitek 2 had the lowest EA and CA, especially for ceftazidime and meropenem. For all three methods, there was a trend of lower minimum inhibitory concentrations and increased Susceptible results in comparison to the reference broth microdilution method, resulting in a high number of VME. While none of the methods met acceptance criteria, Sensititre may offer the best commercially available option for clinical laboratories in circumstances where antimicrobial susceptibility testing is warranted.

Antimicrobial susceptibility testing (AST) of Burkholderia cepacia complex isolates remains of interest due to their inherent multidrug resistance. Previous studies have demonstrated unreliable performance of various methods. As clinical laboratories seek options to perform testing in cases where AST is needed, this study provides data on the performance of three commercially available methods: the Biomerieux Vitek 2, Thermo Scientific Sensititre panels, and the Biomerieux Etest.