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CC BY-NC-ND 4.0 · J Lab Physicians 2021; 13(04): 374-379
DOI: 10.1055/s-0041-1732489
Original Article

Evaluation of the Performance of Direct Susceptibility Test by VITEK-2 from Positively Flagged Blood Culture Broth for Gram-Negative Bacilli

D Kavipriya
1   Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
,
Suman Susan Prakash
1   Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
,
Sarumathi Dhandapani
1   Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
,
Deepashree Rajshekar
1   Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
,
Apurba Sankar Sastry
1   Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
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Abstract

Background Timely initiation of antimicrobial therapy in patients with blood stream infection is absolutely necessary to reduce mortality and morbidity. Most clinical microbiology laboratories use conventional methods for identification and antimicrobial susceptibility testing (AST) that involve biochemical methods for identification followed by AST by disk diffusion. The aim of the current study is to assess the various errors associated with direct susceptibility testing done from blood culture broth using automated AST system-Vitek-2 compact compared with the reference method of AST done from bacterial colonies.

Materials and Methods The study was conducted in a tertiary care public sector 2,200-bedded hospital in South India for a period of 6 months. The study involved positively flagged blood culture bottles that yielded single morphotype of Gram-negative organism by Gram stain. A total of 120 bacterial isolates were collected that consisted of consecutively obtained first 60 isolates of Enterobacteriaceae family (30 Escherichia coli and 30 Klebsiella pneumoniae) and consecutively obtained first 60 nonfermenters (30 Pseudomonas aeruginosa and 30 Acinetobacter baumannii). Vitek-2 AST was done from these 120 blood culture broth, following the protocol by Biomerieux, and results were obtained. Then, Vitek-2 was done from colonies (reference method) using appropriate panel for Enterobacteriaceae and nonfermenters, and results were obtained. Both the results were compared.

Results Nonfermenters showed a better categorical agreement of 97.6%, as compared to Enterobacteriaceae, which showed 97%. Among Enterobacteriaceae, both E. coli and K. pneumoniae showed categorical agreement of 97% each.

Conclusion The procedure of AST directly from blood culture broth represents a simple and effective technique that can reduce the turnaround time by 24 hours, which in turn benefits the clinician in appropriate utilization of antimicrobials for better patient care.

Keywords

antimicrobial susceptibility testing - bloodstream infections - categorical agreement - essential agreement - Enterobacteriaceae - nonfermenters - Vitek-2


Publication History

Article published online:
09 July 2021

© 2021. The Indian Association of Laboratory Physicians. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/).

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