scholarly journals Comparative evaluation of susceptibility testing methods for colistin and polymyxin B among clinical isolates of carbapenem- resistant Klebsiella pneumoniae and Acinetobacter baumannii

2018 ◽  
Vol 12 (06) ◽  
pp. 504-507 ◽  
Author(s):  
Yamuna Devi Bakthavatchalam ◽  
Abirami Shankar ◽  
Bhuvaneswari Thukaram ◽  
Dhanabhagyam Naveena Krishnan ◽  
Balaji Veeraraghavan
Keyword(s):  
Comparative Evaluation ◽  
Susceptibility Testing ◽  
Reference Method ◽  
Polymyxin B ◽  
Disc Diffusion ◽  
Broth Microdilution ◽  
Testing Methods ◽  
Carbapenem Resistant ◽  
Clinical Laboratories ◽  
Vitek 2

Susceptibility testing (ST) of colistin and polymyxin B is challenging. Disc diffusion testing is not reliable for polymyxin ST, because of poor diffusion. Currently, for polymyxin ST, the EUCAST-CLSI joint commission recommending broth microdilution (BMD) as the reference method.  In this study, reliability of E-test and Vitek 2 was compared with BMD, using the susceptible breakpoint of ≤ 2μg/ml for both colistin and polymyxin B.  Overall, essential agreement (EA) for colistin between E-test, Vitek2 and BMD were 37% and 74% respectively. EA for polymyxin B between E-test and BMD were 65%. Very major error (VME) for colistin and polymyxin B with E-test were 42% and 55% respectively. An unacceptable VME of 11% was seen for colistin with Vitek2. Major errors (MEs) were rather limited with both E-test and Vitek2. E-test and Vitek2 may lead to inappropriate decision-making for colistin/polymyxin B therapy. Thus, clinical laboratories should consider BMD for polymyxin ST.

scholarly journals Colistin and Polymyxin B Susceptibility Testing for Carbapenem-Resistant and mcr -Positive Enterobacteriaceae: Comparison of Sensititre, MicroScan, Vitek 2, and Etest with Broth Microdilution

2017 ◽  
Vol 55 (9) ◽  
pp. 2609-2616 ◽  
Author(s):  
Ka Lip Chew ◽  
My-Van La ◽  
Raymond T. P. Lin ◽  
Jeanette W. P. Teo
Keyword(s):  
Susceptibility Testing ◽  
Polymyxin B ◽  
Error Rates ◽  
Test Results ◽  
Broth Microdilution ◽  
Major Error ◽  
Testing Methods ◽  
Content Type ◽  
Carbapenem Resistant ◽  
Vitek 2

ABSTRACT Colistin and polymyxin B remain part of the last line of antibiotics for multidrug-resistant Gram-negative bacteria, such as carbapenem-resistant Enterobacteriaceae . Current joint EUCAST-CLSI recommendations are for broth microdilution (BMD) to be performed for MIC testing of colistin. Commercial susceptibility testing methods were evaluated and compared against the reference BMD, using a susceptibility breakpoint of ≤2 mg/liter for both colistin and polymyxin B. Seventy-six Enterobacteriaceae were included, of which 21 were mcr-1 positive (18 Escherichia coli isolates, 2 Klebsiella pneumoniae isolates, and 1 Enterobacter aerogenes isolate). Rates of essential agreement (EA) of colistin test results between BMD and Vitek 2, Sensititre, and Etest were 93.4%, 89.5%, and 75.0%, respectively. Rates of EA of polymyxin B test results between BMD and Vitek 2, Sensititre, and Etest were 96.1%, 96.1%, and 48.7%, respectively. A positive MIC correlation with a categorical agreement of >90% was achieved for Sensititre (colistin Spearman's ρ = 0.863, and polymyxin B Spearman's ρ = 0.877) and Vitek 2 (polymyxin B [only] Spearman's ρ = 0.8917). Although a positive MIC correlation (Spearman's ρ = 0.873) with the reference method was achieved for colistin testing with Vitek 2, categorical agreement was <90%, with very major error rates of 36%. Correlation with the Etest MIC was lower, with very major error rates of 12% (colistin) and 26.1% (polymyxin B). MicroScan (colistin) categorical agreement was 88.2%, with a very major error rate of 4%. Colistin MICs for 15 of the 21 mcr-1 -positive isolates were >2 mg/liter, and polymyxin MICs for 17 of them were >2 mg/liter by broth microdilution. The use of a lower breakpoint of ≤1 mg/liter further improves detection of mcr-1 for all testing methods. However, further data on the correlation between MICs and clinical outcome are required to determine the most suitable breakpoint to guide clinical management.

scholarly journals Performance of Vitek 2 for Antimicrobial Susceptibility Testing of Enterobacteriaceae with Vitek 2 (2009 FDA) and 2014 CLSI Breakpoints

2014 ◽  
Vol 53 (3) ◽  
pp. 816-823 ◽  
Author(s):  
April M. Bobenchik ◽  
Eszter Deak ◽  
Janet A. Hindler ◽  
Carmen L. Charlton ◽  
Romney M. Humphries
Keyword(s):  
Antimicrobial Susceptibility ◽  
Antimicrobial Agents ◽  
Susceptibility Testing ◽  
Test System ◽  
Broth Microdilution ◽  
Antimicrobial Susceptibility Test ◽  
Content Type ◽  
Carbapenem Resistant ◽  
Clinical Laboratories ◽  
Vitek 2

Vitek 2 (bioMérieux Inc., Durham, NC) is a widely used commercial antimicrobial susceptibility test system. We compared the MIC results obtained using the Vitek 2 AST-GN69 and AST-XN06 cards to those obtained by CLSI broth microdilution (BMD) for 255 isolates ofEnterobacteriaceae, including 25 isolates of carbapenem-resistantEnterobacteriaceae. In total, 25 antimicrobial agents were examined. For 10 agents, the MIC data were evaluated using two sets of breakpoints: (i) the Vitek 2 breakpoints, which utilized the 2009 FDA breakpoints at the time of the study and are equivalent to the 2009 CLSI M100-S19 breakpoints, and (ii) the 2014 CLSI M100-S24 breakpoints. There was an overall 98.7% essential agreement (EA). The categorical agreement was 95.5% (CA) using the Vitek 2 breakpoints and 95.7% using the CLSI breakpoints. There was 1 very major error (VME) (0.05%) observed using the Vitek 2 breakpoints (cefazolin) and 8 VMEs (0.5%) using the CLSI breakpoints (2 each for aztreonam, cefepime, and ceftriaxone, and 1 for cefazolin and ceftazidime). Fifteen major errors (MEs) (0.4%) were noted using the Vitek 2 breakpoints and 8 (0.5%) using the CLSI breakpoints. Overall, the Vitek 2 performance was comparable to that of BMD for testing a limited number ofEnterobacteriaceaecommonly isolated by clinical laboratories. Ongoing studies are warranted to assess performance in isolates with emerging resistance.

Comparative evaluation of minocycline susceptibility testing methods in carbapenem-resistant Acinetobacter baumannii

2016 ◽  
Vol 48 (3) ◽  
pp. 321-323 ◽  
Author(s):  
Pavlos Dimitriadis ◽  
Efthymia Protonotariou ◽  
Sotiris Varlamis ◽  
Aggeliki Poulou ◽  
Olga Vasilaki ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Comparative Evaluation ◽  
Susceptibility Testing ◽  
Testing Methods ◽  
Carbapenem Resistant

scholarly journals Multicenter Evaluation of Colistin Broth Disk Elution and Colistin Agar Test: a Report from the Clinical and Laboratory Standards Institute

2019 ◽  
Vol 57 (11) ◽  
Author(s):  
Romney M. Humphries ◽  
Daniel A. Green ◽  
Audrey N. Schuetz ◽  
Yehudit Bergman ◽  
Shawna Lewis ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antimicrobial Susceptibility ◽  
Susceptibility Testing ◽  
Polymyxin B ◽  
Antimicrobial Susceptibility Testing ◽  
Broth Microdilution ◽  
Content Type ◽  
Clinical Laboratories

ABSTRACT Susceptibility testing of the polymyxins (colistin and polymyxin B) is challenging for clinical laboratories. The Clinical and Laboratory Standards Institute (CLSI) Antimicrobial Susceptibility Testing Subcommittee evaluated two methods to enable accurate testing of these agents. These methods were a colistin broth disk elution (CBDE) and a colistin agar test (CAT), the latter of which was evaluated using two inoculum volumes, 1 μl (CAT-1) and 10 μl (CAT-10). The methods were evaluated using a collection of 270 isolates of Enterobacterales, 122 Pseudomonas aeruginosa isolates, and 106 Acinetobacter spp. isolates. Overall, 94.4% of CBDE results were in essential agreement and 97.9% in categorical agreement (CA) with reference broth microdilution MICs. Nine very major errors (VME; 3.2%) and 3 major errors (ME; 0.9%) were observed. With the CBDE, 98.6% CA was observed for Enterobacterales (2.5% VME, 0% ME), 99.3% CA was observed for P. aeruginosa (0% VME, 0.7% ME), and 93.1% CA was observed for Acinetobacter spp. (5.6% VME, 3.3% ME). Overall, CA was 94.9% with 6.8% VME using CAT-1 and improved to 98.3% with 3.9% VME using CAT-10. No ME were observed using either CAT-1 or CAT-10. Using the CAT-1/CAT-10, the CA observed was 99.4%/99.7% for Enterobacterales (1%/0.5% VME), 98.7%/100% for P. aeruginosa (8.3%/0% VME), and 88.5%/92.3% for Acinetobacter spp. (21.4%/14.3% VME). Based on these data, the CLSI antimicrobial susceptibility testing (AST) subcommittee endorsed the CBDE and CAT-10 methods for colistin testing of Enterobacterales and P. aeruginosa.

scholarly journals Evaluation of Calcium-Enhanced Media for Colistin Susceptibility Testing by Gradient Agar Diffusion and Broth Microdilution

2019 ◽  
Vol 58 (2) ◽  
Author(s):  
Daniel A. Green ◽  
Nenad Macesic ◽  
Anne-Catrin Uhlemann ◽  
Mabel Lopez ◽  
Stephania Stump ◽  
...  
Keyword(s):  
Susceptibility Testing ◽  
Poor Performance ◽  
Polymyxin B ◽  
Multidrug Resistant ◽  
High Rate ◽  
Broth Microdilution ◽  
Content Type ◽  
Agar Diffusion ◽  
Clinical Laboratories ◽  
Susceptible Patient

ABSTRACT Despite the increasing reliance on polymyxin antibiotics (polymyxin B and colistin) for treatment of multidrug-resistant Gram-negative infections, many clinical laboratories are unable to perform susceptibility testing due to the lack of accurate and reliable methods. Although gradient agar diffusion is commonly performed for other antimicrobials, its use for polymyxins is discouraged due to poor performance characteristics. Performing gradient agar diffusion with calcium enhancement of susceptibility testing media has been shown to improve the identification of polymyxin-resistant isolates with plasmid-mediated resistance (mcr-1). We therefore sought to evaluate the broad clinical applicability of this approach for colistin susceptibility testing by assessing a large and diverse collection of resistant and susceptible patient isolates collected from multiple U.S. medical centers. Among 217 isolates, the overall categorical and essential agreement for calcium-enhanced gradient agar diffusion were 73.7% and 65.5%, respectively, compared to the results for reference broth microdilution. Performance varied significantly by organism group, with agreement being highest for Enterobacterales and lowest for Pseudomonas aeruginosa. Nevertheless, even for Enterobacterales, there was a high rate of very major errors (9.2%). Performance was similarly poor for calcium-enhanced broth microdilution. While calcium enhancement did allow for more accurate categorization of mcr-1-resistant isolates, there were unacceptably high rates of errors for both susceptible and non-mcr-1-resistant isolates, raising serious doubts about the suitability of these calcium-enhanced methods for routine colistin susceptibility testing in clinical laboratories.

scholarly journals Comprehensive Statistical Evaluation of Etest®, UMIC®, MicroScan and Disc Diffusion versus Standard Broth Microdilution: Workflow for an Accurate Detection of Colistin-Resistant and Mcr-Positive E. coli

Antibiotics ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 861
Author(s):  
Isidro García-Meniño ◽  
Pilar Lumbreras ◽  
Pablo Valledor ◽  
Dafne Díaz-Jiménez ◽  
Luz Lestón ◽  
...  
Keyword(s):  
Susceptibility Testing ◽  
Statistical Evaluation ◽  
Disc Diffusion ◽  
Broth Microdilution ◽  
Colistin Resistance ◽  
Testing Methods ◽  
Disc Diffusion Assay ◽  
E Coli ◽  
Diffusion Assay ◽  
Microscan System

Four colistin susceptibility testing methods were compared with the standard broth microdilution (BMD) in a collection of 75 colistin-susceptible and 75 mcr-positive E. coli, including ST131 isolates. Taking BMD as reference, all methods showed similar categorical agreement rates (CA) of circa 90%, and a low number of very major errors (VME) (0% for the MicroScan system and Etest®, 0.7% for UMIC®), except for the disc diffusion assay (breakpoint ≤ 11 mm), which yielded false-susceptible results for 8% of isolates. Of note is the number of mcr-positive isolates (17.3%) categorized as susceptible (≤2 mg/L) by the BMD method, but as resistant by the MicroScan system. ST131 mcr-positive E. coli were identified as colistin-resistant by all MIC-based methods. Our results show that applying the current clinical cut-off (>2 mg/L), many mcr-positive E. coli remain undetected, while applying a threshold of >1 mg/L the sensitivity of detection increases significantly without loss of specificity. We propose two possible workflows, both starting with the MicroScan system, since it is automated and, importantly, it categorized all mcr-positive isolates as colistin-resistant. MicroScan should be followed by either BMD or MIC-based commercial methods for colistin resistance detection; or, alternatively, MicroScan, followed by PCR for the mcr screening.

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