Comparative Evaluation of Microbroth dilution, E-strip and Vitek-2 for Colistin susceptibility among Carbapenem resistant Acinetobacter and Klebsiella spp

• Monisha Basavaraju,*  
• M Raghavendra Rao,  
• Ranjitha Shankaregowda,  
• Rashmi Mahale,  
• Sowmya G Shivappa,  
• Vidyavathi B Chitharagi

Abstract

Background: Gram-negative bacterial infections that are resistant to carbapenems are a serious clinical problem. The only effective drugs against them are still tigecycline and colistin. In fact, polymyxin E, also known as colistin, has been regarded as a "last resort" antibiotic. But in recent years, colistin resistance has increased globally, significantly reducing treatment options and highlighting the significance of accurate colistin testing methods to support appropriate therapeutic decision-making. Methodology: The primary goal of the study is to compare the effectiveness of E-test and Vitek 2 for colistin sensitivity testing to the conventional microbroth dilution method using 120 clinical isolates of Klebsiella pnuemoniae and Acinetobacter baumannii that are resistant to carbapenem over the course of a year, from January to December 2019. Results: In comparison to Vitek-2, the results indicated that BMD and E-test produced the narrowest range of colistin MICs. After comparing the E-test's errors and overall agreement with BMD, 100% of the EAs, 94.27% of the CAs, and 5.72% of the VMEs with no MEs were found. Comparing Vitek-2 with BMD, similar results were found: 1.66% MEs, 98.32% CAs, 80.99% EAs, and no VMEs. Conclusion: As a result, it was determined that, in contrast to Vitek-2, MBD and E-test had distinct MICs, making them appropriate for determining colistin MIC. It will take more research on automated systems to standardize colistin susceptibility testing procedures.

Keywords

Broth Microdilution, Carbapenem, colistin, E-test, Vitek 2