Comparative evaluation of susceptibility testing methods for colistin and polymyxin B among clinical isolates of carbapenem- resistant Klebsiella pneumoniae and Acinetobacter baumannii

  • Yamuna Devi Bakthavatchalam Research Associate
  • Abirami Shankar Senior demonstrator
  • Bhuvaneswari Thukaram Microbiologist
  • Dhanabhagyam Naveena Krishnan Microbiologist
  • Balaji Veeraraghavan Christian Medical College
Keywords: Acinetobacter baumannii, colistin, Klebsiella pneumonaie, polymyxin B

Abstract

Susceptibility testing (ST) of colistin and polymyxin B is challenging. Disc diffusion testing is not reliable for polymyxin ST, because of poor diffusion. Currently, for polymyxin ST, the EUCAST-CLSI joint commission recommending broth microdilution (BMD) as the reference method.  In this study, reliability of E-test and Vitek 2 was compared with BMD, using the susceptible breakpoint of ≤ 2μg/ml for both colistin and polymyxin B.  Overall, essential agreement (EA) for colistin between E-test, Vitek2 and BMD were 37% and 74% respectively. EA for polymyxin B between E-test and BMD were 65%. Very major error (VME) for colistin and polymyxin B with E-test were 42% and 55% respectively. An unacceptable VME of 11% was seen for colistin with Vitek2. Major errors (MEs) were rather limited with both E-test and Vitek2. E-test and Vitek2 may lead to inappropriate decision-making for colistin/polymyxin B therapy. Thus, clinical laboratories should consider BMD for polymyxin ST.

Author Biography

Balaji Veeraraghavan, Christian Medical College

Professor and Head

Department of Clinical Microbiology

Christian Medical College

Vellore

Published
2018-06-30
How to Cite
1.
Bakthavatchalam Y, Shankar A, Thukaram B, Krishnan D, Veeraraghavan B (2018) Comparative evaluation of susceptibility testing methods for colistin and polymyxin B among clinical isolates of carbapenem- resistant Klebsiella pneumoniae and Acinetobacter baumannii. J Infect Dev Ctries 12:504-507. doi: https://doi.org/10.3855/jidc.9660
Section
Letters to the Editor