Multicenter Evaluation of Ceftazidime-Avibactam Susceptibility Testing of Enterobacterales and Pseudomonas aeruginosa on the VITEK® 2 System

In this multisite study, VITEK® 2 AST-Gram-Negative Ceftazidime-Avibactam (CZA) test results for 1073 isolates (866 Enterobacterales and 207 Pseudomonas aeruginosa) were compared to the Clinical & Laboratory Standards Institute (CLSI) broth microdilution (BMD) reference method. The results were analyzed for essential agreement (EA), category agreement (CA), major error rates, and very major error rates following FDA/ISO performance criteria using the FDA-recognized CLSI/EUCAST breakpoints (S ≤8/4 μg/ml and R ≥16/4 μg/ml). The overall EA was 94.5% (1014/1073) and CA was 98.7% (1059/1073). No very major errors were reported. The major error rate was 1.4% (14/998). Out of 14 major errors, 9 were within EA. Based on the EA and lack of an intermediate category for CZA, the adjusted major error rate for FDA criteria was 0.5% (5/998). The performance for ISO criteria after error resolutions included EA 94.5% (1014/1073), CA 98.9% (1061/1073), major error 1.2% (12/998), and no very major error. Vitek 2 met the ISO and FDA criteria of ≥95% reproducibility and ≥95% quality control (QC) results within acceptable ranges for QC organisms. Vitek 2 overall performance for Enterobacterales and P. aeruginosa met or exceeded the FDA and ISO performance criteria and thus is a reliable alternative to BMD reference method for routine CZA susceptibility testing.

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

Journal of Clinical Microbiology ◽

10.1128/jcm.00268-17 ◽

2017 ◽

Vol 55 (9) ◽

pp. 2609-2616 ◽

Cited By ~ 78

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.

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Multicenter clinical evaluation of VITEK® 2 meropenem-vaborbactam for susceptibility testing of Enterobacterales and Pseudomonas aeruginosa

Journal of Clinical Microbiology ◽

10.1128/jcm.01610-21 ◽

2021 ◽

Author(s):

Hari P. Dwivedi ◽

Simone Franklin ◽

Sukantha Chandrasekaran ◽

Omai Garner ◽

Maria M. Traczewski ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Susceptibility Testing ◽

Automated System ◽

Individual Species ◽

Method Performance ◽

Overall Performance ◽

Vitek 2 ◽

Tract Infections ◽

Alternate Solution ◽

After Error

The carbapenem/beta-lactamase inhibitor (meropenem-vaborbactam; MEV) used to treat complicated urinary tract infections and pyelonephritis in adults was approved in 2017 by the U.S. Food and Drug Administration (FDA). We evaluated VITEK 2 MEV (bioMérieux, Durham, NC) compared to the reference broth microdilution (BMD) method. Of 449 Enterobacterales isolates analyzed per FDA/CLSI breakpoints, overall performance was 98.2% Essential Agreement (EA), 98.7% Category Agreement (CA), and 0% Very Major Errors (VME) or Major Errors (ME). For FDA intended for use 438 Enterobacterales isolates, performance was 98.2% EA, 98.6% CA, and 0% VME or ME. Evaluable EA was 81.0% but with only 42 on-scale evaluable results. Individual species demonstrated EA and CA rates ≥ 90% without any VME or ME. When evaluated using European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, overall VITEK 2 MEV performance for Enterobacterales and Pseudomonas aeruginosa demonstrated 97.3% EA, 99.2% CA, 2.3% VME, and 0.6% ME (after error resolution: 97.3% EA, 99.4% CA, 2.2% VME, and 0.4% ME) compared to the reference BMD method. Performance for P. aeruginosa included 92.2% EA, 97.4% CA, 0% VME, and 3.0% ME (after error resolution: 92.2% EA, 98.7% CA, 0% VME, and 1.5% ME). Performance for Enterobacterales included 98.2% EA, 99.6% CA, 3.0% VME, and 0.2% ME. Evaluable EA was 80.6% but due to only 67 evaluable results. These findings support VITEK 2 MEV as an accurate automated system for MEV susceptibility testing of Enterobacterales and P. aeruginosa and could be an alternate solution to the manual labor intensive reference BMD method.

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1222. Fosfomycin Susceptibility Testing using the new ETEST®FO

Open Forum Infectious Diseases ◽

10.1093/ofid/ofaa439.1407 ◽

2020 ◽

Vol 7 (Supplement_1) ◽

pp. S632-S632

Author(s):

Diane Halimi ◽

Marion Pompilio ◽

Sandrine Fontaine ◽

Roland Martelin ◽

Christine Franceschi ◽

...

Keyword(s):

Error Rate ◽

Reference Method ◽

Ambient Air ◽

Performance Criteria ◽

Study Phase ◽

Major Error ◽

E Coli ◽

Wide Range ◽

Agar Dilution ◽

Tract Infections

Abstract Background Fosfomycin (FO) is a bactericidal antibiotic with a broad spectrum of activity against a wide range of Gram-positive and Gram-negative bacteria. Oral FO is mainly used in the treatment of urinary tract infections, particularly those caused by E. coli and E. faecalis. In order to determine MICs to FO, the ETEST® FM is already available but the reading can be difficult especially with E. coli. To resolve this issue, a new ETEST® with FO, called ETEST® FO, has been developed (not FDA cleared, yet). The purpose of this study is to compare this new strip to the agar dilution reference method (AD) on a panel of E. coli and E. faecalis. Methods A total of 39 isolates comprising 20 E. coli (ESBL or CPE) and 19 E. faecalis (VRE or VSE) were tested by ETEST® FO and Agar dilution. The isolates were sub-cultured on Columbia agar plates supplemented with 5% sheep blood before testing. After incubation, suspensions of the isolates were prepared in 0.85% saline. These suspensions were used to inoculate both AD and ETEST® plates. Results were read after 16-20 hours incubation at 35°C +2°C in ambient air. Following CLSI QC guideline, 4 QC organisms were tested. Results were analyzed using the FDA/CLSI breakpoints for FO (S < 64µg/mL, I=128 µg/mL, R> 256 µg/mL). Performance was evaluated using FDA performance criteria, essential agreement (EA, ≥ 90%), category agreement (CA, ≥ 90%), major error rate (ME, ≤3.0%) and very major error rate (VME, ≤2.0%). Results All the QC strains MICs were within the CLSI ranges. For the panel results, see the table below: Performance for ETEST® FO on E. coli and E. faecalis Conclusion This first and preliminary study shows that ETEST® FO can potentially meet the FDA acceptance criteria and could be a valuable tool for determining FO MIC for E. coli harboring various resistance mechanisms and E. faecalis including VRE. Moreover, in comparison with the current ETEST FM strip, this new strip brings a real reading improvement and resolve the issue for E. coli. The clinical study phase will determine the product’s performance. Disclosures Marion Pompilio, BioMérieux (Employee) Gilles Zambardi, biomerieux (Employee)

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Detecting In-Vitro Colistin Resistance- A Comparative Study Between Broth Microdilution Versus Vitek-2 For Colistin Susceptibility Testing

Annals of Pathology and Laboratory Medicine ◽

10.21276/apalm.2720 ◽

2020 ◽

Vol 7 (7) ◽

pp. A336-340

Author(s):

Hena Butta ◽

Leena Mendiratta ◽

Raman Sardana ◽

Kirti Gilotra ◽

Sana Hasan ◽

...

Keyword(s):

Escherichia Coli ◽

Pseudomonas Aeruginosa ◽

Clinical Microbiology ◽

Susceptibility Testing ◽

Clinical Microbiology Laboratory ◽

Microbiology Laboratory ◽

Broth Microdilution ◽

Major Error ◽

Acinetobacter Baumanii ◽

Vitek 2

Background: Susceptibility testing for polymyxins is a great challenge for a Clinical Microbiology laboratory. There are several methodological issues associated with MIC (Minimum Inhibitory Concentration) determination of colistin. Methods: In our study, we have compared the results of colistin susceptibility testing by Automated system (Vitek-2, Biomerieux, France) with the reference Broth Microdilution method (BMD) to identify the type of discrepancies by Vitek-2 method and thus develop a practical and accurate approach for colistin susceptibility testing in a Clinical Microbiology laboratory. A total of 730 strains of Gram negative bacteria [Escherichia coli (325), Klebsiella sp.(346), Acinetobacter baumanii complex (37) and Pseudomonas aeruginosa (22)] from 485 patents were tested simultaneously by BMD and Vitek-2 method for colistin susceptibility testing. Results: The Essential agreement (EA), Categorical agreement (CA), Very major error (VME) and Major error (ME) rates for Klebsiella sp. were 87.3%, 89.3%, 8% and 2.3% respectively, for Escherichia coli were 88.3%, 89.5%, 9.2% and 1.2% respectively, for Acinetobacter baumannii complex were 89.1%, 91.8%, 8.1% and 0% respectively, for Pseudomonas aeruginosa were 68.1%, 72.7%, 0% and 27.2% respectively. Conclusions: Colistin susceptibility testing by Vitek-2 method is an easily adoptable method and the results of Vitek-2 with reference to BMD are acceptable to a great extent in Klebsiella sp., Escherichia coli and Acinetobacter baumanii complex. So, we believe that Vitek-2 method may be used for colistin susceptibility testing in low risk patients. However, BMD should be used in high risk immunosupressed and immunocompromised patients who are admitted in critical care units. For Pseudomonas aeruginosa, BMD should be routinely used.

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Evaluation of Vitek®2 performance for colistin susceptibility testing for Gram-negative isolates

JAC-Antimicrobial Resistance ◽

10.1093/jacamr/dlaa101 ◽

2020 ◽

Vol 2 (4) ◽

Author(s):

Surbhi Khurana ◽

Rajesh Malhotra ◽

Purva Mathur

Keyword(s):

Susceptibility Testing ◽

Reference Method ◽

Trauma Centre ◽

Gram Negative Bacteria ◽

Test Results ◽

Major Error ◽

Colistin Resistance ◽

Testing Methods ◽

Gram Negative ◽

Unreliable Method

Abstract Background The emerging resistance to the last-resort antimicrobial colistin is being reported globally. Underestimation of the burden of colistin resistance and misinterpretation of colistin susceptibility test results, using suboptimal testing methods, may be causing unexplained treatment failures and even mortality among critically ill patients. Thus, this study was conducted at an apex trauma centre to assess the performance of Vitek®2 for colistin susceptibility testing. Methods A total of 910 clinical isolates of Gram-negative bacteria (GNB), including Enterobacterales, Acinetobacter baumannii and Pseudomonas aeruginosa, were tested and analysed for colistin resistance using Vitek®2. Broth microdilution (BMD) was taken as the reference method. The essential (EA) and categorical (CA) agreements and very major error (VME) and major error (ME) rates were calculated. An MIC correlation was taken to be positive with EA ≥ 90%, CA ≥ 90%, VME ≤ 1.5% and ME ≤ 3.0% rates. Spearman’s coefficient was calculated and P < 0.05 was considered statistically significant. Results A total of 64% of isolates were MDR. Overall, 196 (21.5%) and 110 (12%) of isolates were resistant to colistin by BMD and Vitek®2, respectively. The automated Vitek®2 method failed to detect the resistance in up to 48.5% of GNB tested. When comparing Vitek®2 colistin interpretive results with reference BMD for all 910 isolates, the CA was 88% (798/910) with 10% (95/910) VMEs and 1% (9/910) MEs. Conclusions The Vitek®2 method for colistin susceptibility testing, still in use in some settings; is a suboptimal and unreliable method.

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1227. Plazomicin Susceptibility Testing using ETEST® MIC for Enterobacterales

Open Forum Infectious Diseases ◽

10.1093/ofid/ofaa439.1412 ◽

2020 ◽

Vol 7 (Supplement_1) ◽

pp. S634-S634

Author(s):

Yun Ying ◽

Tom Armstrong ◽

Laurine Blanchard ◽

Michael Kresken ◽

Gilles Zambardi ◽

...

Keyword(s):

Error Rate ◽

Clinical Performance ◽

Treatment Options ◽

Klebsiella Oxytoca ◽

Reference Method ◽

Ambient Air ◽

Performance Criteria ◽

Major Error ◽

High Level ◽

Tract Infections

Abstract Background Plazomicin (PLZ) approved by FDA in June of 2018, is an aminoglycoside class antibacterial indicated for the treatment of adults with complicated urinary tract infections (cUTI) including pyelonephritis caused by Enterobacterales. It is used in patients who have limited or no alternative treatment options, e.g. CRE and MDRO patients. The drug has bactericidal activity, it is active against organisms producing ESBL, Carbapenemase and aminoglycoside-modifying enzymes. The purpose of this study was to compare ETEST® PLZ bioMérieux to the broth microdilution reference method (BMD) for Citrobacter freundii, Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca and pneumoniae, Morganella morganii, Providencia stuartii, Proteus mirabilis and vulgaris and Serratia marcescens isolates. Methods A total of 598 isolates were tested by ETEST® (PLZ) and BMD at four clinical trial sites. Isolates were subcultured on tryptic soy or Columbia agar plates supplemented with 5% sheep blood. Suspensions of the isolates were prepared in 0.85% saline, which were used to inoculate BMD and Mueller Hinton agar for ETEST®. Results were read after 16-20 hours incubation at 35°C +2°C in ambient air. QC organisms were tested with each run following CLSI QC guidelines. Results were analyzed using FDA breakpoints for PLZ (Susceptible <2 µg/mL, Intermediate 4 µg/mL, Resistant >8 µg/mL). Performance was evaluated using FDA performance criteria, EA and CA (≥ 90%), major error rate (≤3.0%) and very major error rate (≤2.0%). Results Conclusion ETEST® PLZ clinical performance met the FDA acceptance criteria and was found useful for determining Plazomicin MIC of Enterobacterales, including ESBL, CRE (MBL, KPC, Oxa-48), high level AmpC and aminoglycoside resistant strains. Percent susceptibility of Plazomicin is at 80% among the 598 isolates tested, the mode MIC is 0.5 ug/ml as Susceptible. Disclosures Tom Armstrong, BS, bioMérieux (Employee) Laurine Blanchard, PhD, bioMérieux (Employee) Michael Kresken, PhD, bioMérieux (Scientific Research Study Investigator, Research Grant or Support) Gilles Zambardi, biomerieux (Employee) Marion Pompilio, BioMérieux (Employee)

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Evaluation of Diagnostics Colistin MIC-Strip Test for Colistin Susceptibility Testing

ANKEM Dergisi ◽

10.5222/ankem.2021.009 ◽

2021 ◽

Author(s):

Gülşen Altınkanat Gelmez ◽

Elvan Sayın ◽

Ufuk Hasdemir ◽

Güner Söyletir

Keyword(s):

Error Rate ◽

Susceptibility Testing ◽

Antimicrobial Treatment ◽

Error Rates ◽

Multi Drug Resistance ◽

Routine Laboratory ◽

Broth Microdilution ◽

Major Error ◽

Broth Microdilution Method ◽

Strip Test

Due to the limited number of antimicrobials to be used in the treatment of infections caused by Gram-negative microorganisms with multi-drug resistance recently, old antibiotics such as colistin have started to be preferred frequently. However, some problems are encountered in antibiotic susceptibility tests (disk diffusion, gradient test, automated systems) which are frequently used in the routine laboratory due to the cationic nature of colistin. For this reason, only the broth microdilution test is recommended by European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Clinical and Laboratory Standards Institute (CLSI) for the detection of colistin susceptibility. Since broth microdilution tests are time consuming and inconvenient, tests that can provide fast and reliable colistin susceptibility result is needed in routine laboratories. In this study, it was aimed to evaluate the performance of the commercially produced Diagnostics MIC-COL test (Diagnostics I.n.c, Galanta, Slovakia) for the detection of colistin susceptibility in Klebsiella pneumoniae and Acinetobacter baumannii strains. The strains of K.pneumoniae (n = 22) and A.baumannii (n = 28) isolated from various clinical specimens between 2016 and 2019 in our routine laboratory were included in the study. Colistin minimum inhibitory concentrations (MIC) of the strains were studied with both the reference broth microdilution method and the commercially produced Diagnostics Colistin MIC-COL test. The essential agreement, categorical agreement, major error, and very major error rates of the test were calculated by comparing the obtained results. The essential agreement of the Diagnostics Colistin MIC-Strip test was determined as 84 %, categorical agreement as 98 %, and major error rate as 3.8 %, while no very major error was detected. İt is very important to guide antimicrobial treatment with rapid and reliable detection of colistin susceptibility. The commercial test used in our study is easy to use and not time-consuming. Also, due to its strip from, each isolate can be studied separately. Because of the major error rate being above the expected values, it will be useful to re-evaluate these rates with further studies to be conducted with a larger number of strains with different resistance levels.

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Evaluation of the Performance of Direct Susceptibility Test by VITEK-2 from Positively Flagged Blood Culture Broth for Gram-Negative Bacilli

Journal of Laboratory Physicians ◽

10.1055/s-0041-1732489 ◽

2021 ◽

Author(s):

Kavipriya D. ◽

Suman Susan Prakash ◽

Sarumathi Dhandapani ◽

Deepashree Rajshekar ◽

Apurba Sankar Sastry

Keyword(s):

Blood Culture ◽

Susceptibility Testing ◽

Blood Stream Infection ◽

Tertiary Care ◽

Reference Method ◽

Culture Broth ◽

Timely Initiation ◽

Gram Negative ◽

Mortality And Morbidity ◽

Vitek 2

Abstract Background Timely initiation of antimicrobial therapy in patients with blood stream infection is absolutely necessary to reduce mortality and morbidity. Most clinical microbiology laboratories use conventional methods for identification and antimicrobial susceptibility testing (AST) that involve biochemical methods for identification followed by AST by disk diffusion. The aim of the current study is to assess the various errors associated with direct susceptibility testing done from blood culture broth using automated AST system-Vitek-2 compact compared with the reference method of AST done from bacterial colonies. Materials and Methods The study was conducted in a tertiary care public sector 2,200-bedded hospital in South India for a period of 6 months. The study involved positively flagged blood culture bottles that yielded single morphotype of Gram-negative organism by Gram stain. A total of 120 bacterial isolates were collected that consisted of consecutively obtained first 60 isolates of Enterobacteriaceae family (30 Escherichia coli and 30 Klebsiella pneumoniae) and consecutively obtained first 60 nonfermenters (30 Pseudomonas aeruginosa and 30 Acinetobacter baumannii). Vitek-2 AST was done from these 120 blood culture broth, following the protocol by Biomerieux, and results were obtained. Then, Vitek-2 was done from colonies (reference method) using appropriate panel for Enterobacteriaceae and nonfermenters, and results were obtained. Both the results were compared. Results Nonfermenters showed a better categorical agreement of 97.6%, as compared to Enterobacteriaceae, which showed 97%. Among Enterobacteriaceae, both E. coli and K. pneumoniae showed categorical agreement of 97% each. Conclusion The procedure of AST directly from blood culture broth represents a simple and effective technique that can reduce the turnaround time by 24 hours, which in turn benefits the clinician in appropriate utilization of antimicrobials for better patient care.

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Correlation of cefpodoxime susceptibility with cephalothin and cefuroxime for urinary tract isolates

Journal of Medical Microbiology ◽

10.1099/jmm.0.063040-0 ◽

2014 ◽

Vol 63 (2) ◽

pp. 218-221 ◽

Cited By ~ 3

Author(s):

David A. Bookstaver ◽

Christopher M. Bland ◽

Mitchell W. Woodberry ◽

Karon B. Mansell

Keyword(s):

Escherichia Coli ◽

Urinary Tract ◽

Error Rate ◽

Surrogate Marker ◽

Error Rates ◽

The Other ◽

Colony Count ◽

Major Error ◽

E Coli ◽

Microscan System

This study attempted to determine whether cefuroxime was superior to cephalothin as a surrogate marker for cefpodoxime among urinary tract isolates. The MicroScan system (Siemens) was used to determine susceptibility for cephalothin and cefuroxime on consecutive cultures with a colony count of ≥50 000 organisms. Simultaneously, an Etest (bioMérieux) for cefpodoxime was conducted. The cefpodoxime interpretation was compared to that of the other two agents, and the categorical agreement was calculated, defined as the percentage of identical susceptibility interpretations. Cefuroxime (83 %) had a significantly higher categorical agreement than cephalothin (63 %) among 300 isolates (P<0.01). The major error rate was 16 % for cephalothin and 3 % for cefuroxime. The very major error rate was 7 % for cephalothin and 14 % for cefuroxime among the 14 cefpodoxime-resistant isolates. For Escherichia coli, the major error rates were 15 % and 1 % for cephalothin and cefuroxime, respectively. Very major error rates were 9 % for both agents. Cefuroxime was a better predictor of cefpodoxime susceptibility than cephalothin, and appears to be the preferred surrogate agent for the MicroScan system, particularly for E. coli.

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