Performance of different methods for testing polymyxin B: comparison of broth microdilution, agar dilution and MIC test strip in mcr-1 positive and negative Escherichia coliShow others and affiliations
2021 (English)In: Letters in Applied Microbiology, ISSN 0266-8254, E-ISSN 1472-765X, Vol. 73, no 2, p. 197-205Article in journal (Refereed) Published
Abstract [en]
Antimicrobial susceptibility testing with the last-resort antibiotics polymyxins (polymyxin B and colistin) is associated with several methodological issues. Currently, broth microdilution (BMD) is recommended for colistin and polymyxin B. BMD is laborious and the utility of alternative methods needs to be evaluated for polymyxin B susceptibility testing. In this study, using BMD as a reference method, the performance of agar dilution (AD) and MIC test strips (MTS) were evaluated in polymyxin B susceptibility testing. BMD, AD and MTS were used to determine MICs of 193 clinical isolates of Escherichia coli. Seventy-nine were positive for the polymyxin resistance gene mcr-1. Method performances were evaluated based on pair-wise agreements with the reference method (BMD) and statistical testing. AD and MTS showed an unacceptable number of very major errors (VMEs) compared with BMD, 9 center dot 3 and 10 center dot 7%, respectively. The essential agreement (EA) was low for AD (49 center dot 7%), but high for MTS (97 center dot 8%). However, statistical testing showed that MTS tended to yield a one-step lower MIC (P < 0 center dot 01) compared with BMD. The discordances observed with MTS and AD in comparison with BMD for polymyxin B susceptibility testing for E. coli suggest their inapplicability in routine testing. A large number of isolates clustered around the susceptibility breakpoint (2-4 mg l(-1)) and several mcr-1 positive isolates (17%) were determined as susceptible with BMD. A screening breakpoint for mcr-1 of 2 mg l(-1) should also be considered.
Place, publisher, year, edition, pages
WILEY , 2021. Vol. 73, no 2, p. 197-205
Keywords [en]
agar dilution; antimicrobial susceptibility testing; broth microdilution; Enterobacterales; MIC test strip; mobilized colistin resistance; polymyxin
National Category
Microbiology in the medical area
Identifiers
URN: urn:nbn:se:liu:diva-176836DOI: 10.1111/lam.13492ISI: 000659251200001PubMedID: 33904164OAI: oai:DiVA.org:liu-176836DiVA, id: diva2:1570745
Note
Funding Agencies|Key Research and Development Program of Zhejiang Province [2015C03032]; Swedish Research Council FormasSwedish Research CouncilSwedish Research Council Formas [2016-00640]; Swedish Foundation for International Cooperation in Research and Higher Education (STINT) [CH2016-6707]; ALF-grants, Region _Osterg_otland [LIO-899871]
2021-06-222021-06-222022-04-05