Validation, clinical, and QC data for AST plates and discs

Validation studies show that AST testing with Sensititre plates and Oxoid discs aligns closely with EUCAST and CLSI standards. Output from SWIN software shows the kind of guidance and reports customers can expect when using Sensititre MIC plates and instruments.

Validation studies

Disc diffusion method

Disc diffusion results for discs from nine manufacturers vs EUCAST quality control targets and ranges.

In 2014 and 2017, the European Committee on Antimicrobial Susceptibility Testing (EUCAST) tested AST discs for 16 antimicrobials from nine manufacturers against EUCAST QC target values and ranges. Heat maps highlight adherence to the target ranges. In the 2017 study, only Oxoid (red outline, a Thermo Fisher Scientific brand) discs had a mean value within ±1 mm of the target (color-coded green) for all 16 antimicrobials.

Source: Åhman J, Matuschek E, Kahlmeter G. The quality of antimicrobial discs from nine manufacturers—EUCAST evaluations in 2014 and 2017. Clin Microbiol Infect. 2019; 25: 346-352. Full text

Additional validation studies. The EUCAST development laboratory (EDL) evaluated 21 commercial Mueller–Hinton (MH) dehydrated agar preparations from 17 manufacturers for disc diffusion AST testing. Oxoid MH Agar was one of six preparations that “demonstrated excellent performance, with ≥99% of zone diameter readings within QC ranges and ≥70% on target ±1 mm.” In the study, EDL noted that “discs from Oxoid (Thermo Fisher Scientific) were used due to their accurate and reproducible performance in a previous disc evaluation study” as cited above.

 

Åhman J, Matuschek E, Kahlmeter G. EUCAST evaluation of 21 brands of Mueller–Hinton dehydrated media for disc diffusion testing. Clin Microbiol Infect. 2020; 26: 1412.e1-1412.e5. Full text

Broth microdilution method

Correlation of colistin MIC values between Sensititre and reference broth microdilution (BMD) methods.

EUCAST researchers evaluated five commercial MIC colistin AST testing methods for Gram negative bacteria against the broth microdilution (BMD) standard. Essential agreement (EA) was defined as test MICs either identical with reference MICs (colored green in the graph) or within ±1 dilution (colored yellow). All three panels using the BMD method, including a custom Sensititre plate, had EAs of 96% or above, while EAs for the panels using the gradient method ranged from 43% to 71%. Of all the tests, only the Sensititre plate had no Very Major Errors (false susceptible results) according to EUCAST breakpoint tables.

Source: Matuschek E, Åhman J, Webster C, Kahlmeter G. Evaluation of five commercial MIC methods for colistin antimicrobial susceptibility testing for Gram-negative bacteria. Poster presentation. Full text

Concordance of manual and automated readings of Sensititre MIC plates with BMD MIC panels.

Sensititre susceptibility plates containing five different antimicrobics were read manually (using the Vizion System) and automatically (using the ARIS System) to determine MIC values for Enterobacteriaceae spp., Acinetobacter spp., and Pseudomonas spp. The values were compared with broth microdilution MIC panels manufactured according to ISO 20776-1. Results showed >90% essential agreement (EA) and categorical agreement (CA) by both reading methods for all antimicrobics tested, meeting or exceeding CLSI standards.[1]

Source: Oleksiuk M, Screen J, Scopes E, Bursens J. Evaluation of Thermo Scientific Sensititre Susceptibility MIC plates for the MIC determination of Gram negative isolates for amoxicillin, amoxicillin/clavulanic acid, cefotaxime, meropenem and piperacillin-tazobactam. Poster presentation, 2015. Full text

Additional validation studies. Researchers from France and Switzerland tested 185 Gram-negative clinical isolates on three commercialized broth microdilution systems for colistin susceptibility. They concluded that “the Sensititre system was the most reliable marketed BMD panel with a categorical agreement of 97.8%.”

 

Jayol A, Nordmann P, André C, Poirel L, Dubois V. Evaluation of three broth microdilution systems to determine colistin susceptibility of Gram-negative bacilli. J Antimicrob Chemother. 2018; 73: 1272-1278. PubMed

[1] Humphries RM, Ambler J, Mitchell SL, et al. CLSI Methods Development and Standardization Working Group best practices for evaluation of antimicrobial susceptibility tests. J Clin Microbiol. 2018; 56: e01934-17. PubMed

SWIN software guidance

When you use the Sensititre System, data appears right on the screen. The SWIN software interprets the microbial growth in each well as Susceptible (S, green), Resistant (R, red), or Intermediate (I, yellow) according to the breakpoints set by the regulatory body you have chosen. Clinicians have the option to alter the software interpretation based on their clinical judgment.

SWIN clinical reports

Clinical reports from SWIN software include MIC values and interpretations based on CLSI or EUCAST breakpoints as chosen by the user at setup. Comments from the Expert System reflect on CLSI or EUCAST recommendations and are keyed to individual results.

Sample SWIN clinical report

SWIN clinical reports contain MIC values and interpretations based on CLSI or EUCAST breakpoints. S = Susceptible, R = Resistant, I = intermediate, and NI = No interpretation, signifying that the organism has no breakpoints for that antimicrobic. Expert rules are aligned with CLSI or EUCAST recommendations and can be updated as clinical guidance changes.

SWIN QC reports

When you run a quality control (QC) test on a Sensititre plate, SWIN software outputs complete MIC results for each antimicrobic and QC strain, alongside its acceptable regulatory standard. The report also includes a Pass or Fail grade on five different test elements.

Excerpt from SWIN Software QC report.

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Regulatory status varies by product and region. Please consult individual product pages.