Media for colistin susceptibility testing does not improve the detection of Klebsiella pneumoniae isolates carrying MgrB disruption and other mutation driven colistin resistance mechanisms

• Published in: Diagnostic microbiology and infectious disease Vol. 98; no. 1; p. 115077
• Main Authors: Castanheira, Mariana, Doyle, Timothy B., Carvalhaes, Cecilia G., Roth, Brieanna M., Rhomberg, Paul R., Mendes, Rodrigo E.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-09-2020
• Subjects: Anti-Bacterial Agents - pharmacology; Bacterial Proteins - genetics; Broth microdilution; Colistin - pharmacology; Culture Media - pharmacology; Drug Resistance, Multiple, Bacterial - genetics; Humans; Klebsiella Infections - microbiology; Klebsiella pneumoniae - drug effects; Klebsiella pneumoniae - genetics; mcr; Microbial Sensitivity Tests; Mutation; Polymyxin; Polymyxins - pharmacology; Polymyxin; mcr; Broth microdilution
• ISSN: 0732-8893; 1879-0070
• DOI: 10.1016/j.diagmicrobio.2020.115077

We evaluated different susceptibility testing media against 200 Klebsiella pneumoniae isolates that have been genetically characterized for the presence of polymyxin resistance mechanisms. The media evaluated included calcium enriched media that was described to promote separation of mcr-carrying Enterobacterales isolates and standard cation-adjusted Mueller-Hinton broth with and without polysorbate 80. The testing conditions evaluated did not show improvement in the separation of isolates carrying MgrB alterations and other mutation-driven polymyxin resistance mechanisms.
•The increase in carbapenem-resistant K. pneumoniae led to the increased use of polymyxins.•Detection of polymyxin resistance is challenging for clinical laboratories.•Media described to improve detection of polymyxin resistance was compared to reference methods.•Two hundred K. pneumoniae with most prevalent polymyxin resistance mechanisms were tested.•Testing methods did not allow for better categorization among susceptible and resistant isolates.