• Bijayini Behera, Purva Mathur, Anupam Das, Arti Kapil, Babita Gupta, Sanjeev Bhoi, Kamran Farooque, Vijay Sharma, and M C Misra.
• Department of Laboratory Medicine, Jai Prakash Narain Apex (JPNA) Trauma Centre, All India Institute of Medical Sciences (AIIMS), New Delhi, 110029 India.
• Int. J. Infect. Dis. 2010 Jul 1;14(7):e596-601.

BackgroundThe widespread resistance in Gram-negative bacteria has necessitated evaluation of the use of older antimicrobials such as polymyxins. In the present study we evaluated the different susceptibility testing methods for polymyxins B and E against Gram-negative bacteria using the new Clinical and Laboratory Standards Institute (CLSI) guidelines.MethodsThe susceptibility of 281 multidrug-resistant (MDR) Gram-negative bacteria (GNB) to polymyxin B was evaluated, comparing broth microdilution (BMD; reference method), agar dilution, E-test, and disk diffusion. Disk diffusion testing of polymyxin B was also performed against 723 MDR GNB.ResultsTwenty-four of 281 (8.5%) isolates were found to be resistant to polymyxin B by the reference BMD method. The rates of very major errors for agar dilution and E-test (for polymyxin B) were 0.7% and 1%, respectively, and those for disk diffusion (for polymyxin B and polymyxin E) were 1% and 0.7%, respectively. For the 257 isolates found sensitive by reference BMD, the rates of major errors by agar dilution and E-test (for polymyxin B) were 2.4% and 0%, respectively, and those for disk diffusion (polymyxin B and polymyxin E) were 0% and 0.7%, respectively. Twenty-six (3.6%) of the 723 Gram-negative isolates were resistant to polymyxin B by disk diffusion.ConclusionThe E-test and agar dilution methods showed good concordance with BMD. The disk diffusion method can be useful for initial screening in diagnostic laboratories.Copyright 2009 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

17 keywords...

hide…