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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Cation Concentration Variability of Four Distinct Mueller-Hinton Agar Brands Influences Polymyxin B Susceptibility Results

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Author(s):
Girardello, Raquel [1] ; Bispo, Paulo J. M. [1, 2] ; Yamanaka, Tiago M. [1, 2] ; Gales, Ana C. [1]
Total Authors: 4
Affiliation:
[1] Univ Fed Sao Paulo, Lab Especial Microbiol Clin LEMC ALERIA, Sao Paulo - Brazil
[2] Univ Fed Sao Paulo, Lab Microbiol Ocular & Mol, Sao Paulo - Brazil
Total Affiliations: 2
Document type: Journal article
Source: Journal of Clinical Microbiology; v. 50, n. 7, p. 2414-2418, JUL 2012.
Web of Science Citations: 24
Abstract

Polymyxins have been the only alternative therapeutic option for the treatment of serious infections caused by multidrug-resistant Acinetobacter baumannii or Pseudomonas aeruginosa isolates. For this reason, it is of crucial importance that susceptibility tests provide accurate results when testing these drug-pathogen combinations. In this study, the effect of cation concentration variability found on different commercial brands of Mueller-Hinton agar (MHA) for testing polymyxin B susceptibility was evaluated. The polymyxin B susceptibilities determined using Etest and disk diffusion were compared to those determined by the CLSI reference broth microdilution method. In general, the polymyxin B MIC values were higher when determined by Etest than when determined by broth microdilution against both A. baumannii and P. aeruginosa isolates. A high very major error rate (10%) was observed, as well as a trend toward lower MICs, compared to those determined by broth microdilution when the Merck MHA was tested by Etest. Poor essential agreement rates (10 to 70%) were observed for P. aeruginosa when all MHA brands were tested by Etest. Although an excellent categorical agreement rate (100%) was seen between the disk diffusion and broth microdilution methods for P. aeruginosa, larger zones of inhibition were shown obtained using the Merck MHA. The high cation concentration variability found for the MHA brands tested correlated to the low accuracy, and discrepancies in the polymyxin B MICs were determined by Etest method, particularly for P. aeruginosa isolates. (AU)

FAPESP's process: 10/12891-9 - Evaluation of Pseudomonas aeruginosa, Acinetobacter Baumannii and Klebsiella pneumoniae transcriptomes for elucidation of their polymyxin resistance mechanisms
Grantee:Ana Cristina Gales
Support Opportunities: Regular Research Grants