scholarly journals Performance of commercial methods for linezolid susceptibility testing of Enterococcus faecium and Enterococcus faecalis

2020 ◽  
Vol 75 (9) ◽  
pp. 2587-2593
Author(s):  
Loren Dejoies ◽  
Sarrah Boukthir ◽  
Gauthier Péan de Ponfilly ◽  
Ronan Le Guen ◽  
Asma Zouari ◽  
...  
Keyword(s):  
Enterococcus Faecalis ◽  
Enterococcus Faecium ◽  
Susceptibility Testing ◽  
Reference Method ◽  
Error Rates ◽  
Clinical Isolates ◽  
Broth Microdilution ◽  
Prolonged Incubation ◽  
Automated Methods ◽  
Faecium Isolate

Abstract Background Linezolid-resistant enterococci (LRE) causing infections that are challenging to treat are rising, highlighting the need for reliable screening of LRE clinical isolates. Objectives To evaluate the ability of the broth microdilution (BMD) method for LRE detection and to assess the performance of seven commercially available techniques for linezolid susceptibility testing. Methods A collection of 100 clinical isolates (80 Enterococcus faecium and 20 Enterococcus faecalis), including 20 optrA-positive isolates, 17 poxtA-positive isolates and 1 optrA/poxtA-positive E. faecium isolate, were studied. MICs were determined after 18 h [Day 1 (D1)] and 42 h [Day 2 (D2)] of incubation and interpreted following EUCAST and CLSI guidelines, which currently provide different interpretative breakpoints. Performance of commercial techniques was compared with BMD results. Results MIC50/D1 and MIC50/D2 were both 8 mg/L, while MIC90/D1 and MIC90/D2 were 16 and 32 mg/L, respectively. MICD1 values for poxtA-positive isolates were lower than those for optrA-positive isolates. Proportions of susceptible isolates at D1 and D2 were 48% and 41%, respectively, according to EUCAST breakpoints and 35% and 13%, respectively, according to CLSI criteria (the proportions of isolates categorized as intermediate following CLSI recommendations were 13% and 28% at D1 and D2, respectively). Percentage susceptibility assessed by the commercially available techniques was always higher. The four commercial methods allowing MIC determination provided an overall essential agreement of ≥90% at D1. Categorical agreement and error rates were generally improved at D2. Conclusions Non-automated methods (Sensititre and UMIC) and, to a lesser extent, gradient strip Etest appear to show an acceptable correlation with the BMD reference method for the detection of isolates with low MICs of linezolid after prolonged incubation.

Susceptibility testing of clinical isolates of Enterococcus faecium and Enterococcus faecalis.

1992 ◽  
Vol 30 (1) ◽  
pp. 41-45 ◽  
Author(s):  
M Louie ◽  
A E Simor ◽  
S Szeto ◽  
M Patel ◽  
B Kreiswirth ◽  
...  
Keyword(s):  
Enterococcus Faecalis ◽  
Enterococcus Faecium ◽  
Susceptibility Testing ◽  
Clinical Isolates

Evaluation study of using ampicillin susceptibility to predict imipenem susceptibility of E. faecalis and E. faecium

2019 ◽  
Author(s):  
lanfang guo ◽  
Dandan Yin ◽  
Yan Guo ◽  
Yonggui Zheng ◽  
Qingyu Shi ◽  
...  
Keyword(s):  
Enterococcus Faecalis ◽  
Enterococcus Faecium ◽  
Susceptibility Testing ◽  
Evaluation Study ◽  
Disk Diffusion ◽  
In Vitro Activity ◽  
Broth Microdilution ◽  
Major Error ◽  
Prediction Mode

Abstract Objective: To evaluate ampicillin to predict activity of Enterococcus faecalis and Enterococcus faecium to imipenem. Methods: A total of 127 non-duplicated strains of Enterococcus faecalis and 124 strains of Enterococcus faecium were collected from 23 hospitals in China. The antimicrobial susceptibility testing was determinated using broth microdilution and disk diffusion. Results: For all E. faecalis , when using penicillin/ampicillin results to predict susceptibility to imipenem (called as penicillin-imipenem prediction mode and amipicillin-imipenem mode), the categorical agreement (CA) and major error (ME) rate was 88.9%/95.3% and 6.3%/0%, whereas it was 89.7%/96.8% and 8.7%/1.6%, when using that results of disk diffusion, respectively. No very major error (VME) rate was founded for both prediction modes. For penicillin susceptible, ampicillin susceptible E. faecalis , the CA rate of ampicillin-imipenem prediction mode based on results from broth microdilution and disk diffusion to was both 100%, and neither was founded with VME or ME rate. For penicillin resistant, ampicillin susceptible E. faecalis , the CA rate of ampicillin-imipenem prediction mode based on results from broth microdilution and disk diffusion was 57.1% and 81.8%, respectively. And neither was founded with VME or ME rate. For penicillin resistant, ampicillin resistant E. faecalis , the CA/ME/VME rate of ampicillin-imipenem prediction mode based on results from broth microdilution and disk diffusion was 100%/0%/0% and 77.8%/22.2%/0%, respectively. For all E. faecium , the CA rate of penicillin-imipenem and ampicillin-imipenem prediction mode based on results from broth microdilution was 100% and 99.2%, and it was both 99.2% based on results from disk diffusion. ME and VME rate for all four prediction modes was 0%. For penicillin resistant, ampicillin resistant E. faecium , the CA rate was 100%, as well as penicillin susceptible, ampicillin susceptible E. faecium . None of prediction mode was found with ME or VME rate. Conclusion: For penicillin susceptible, ampicillin susceptible or penicillin resistant, ampicillin resistant E. faecalis and E. faecium , ampicillin susceptibility results of broth microdilution could accurately predict in vitro activity of imipenem. However, for penicillin resistant, ampicillin susceptible E. faecalis and E. faecium , using ampicillin results to predict imipemem susceptibility of was poorly consistent.

scholarly journals Agreement Assessment of Tigecycline Susceptibilities Determined by the Disk Diffusion and Broth Microdilution Methods among Commonly Encountered Resistant Bacterial Isolates: Results from the TigecyclineIn VitroSurveillance in Taiwan (TIST) Study, 2008 to 2010

2011 ◽  
Vol 56 (3) ◽  
pp. 1414-1417 ◽  
Author(s):  
Jien-Wei Liu ◽  
Wen-Chien Ko ◽  
Cheng-Hua Huang ◽  
Chun-Hsing Liao ◽  
Chin-Te Lu ◽  
...  
Keyword(s):  
Susceptibility Testing ◽  
Total Error ◽  
Error Rates ◽  
Resistant Bacteria ◽  
Drug Resistant ◽  
Broth Microdilution ◽  
Content Type ◽  
E Coli ◽  
Drug Resistant Bacteria

ABSTRACTThe TigecyclineIn VitroSurveillance in Taiwan (TIST) study, initiated in 2006, is a nationwide surveillance program designed to longitudinally monitor thein vitroactivity of tigecycline against commonly encountered drug-resistant bacteria. This study compared thein vitroactivity of tigecycline against 3,014 isolates of clinically important drug-resistant bacteria using the standard broth microdilution and disk diffusion methods. Species studied included methicillin-resistantStaphylococcus aureus(MRSA;n= 759), vancomycin-resistantEnterococcus faecium(VRE;n= 191), extended-spectrum β-lactamase (ESBL)-producingEscherichia coli(n= 602), ESBL-producingKlebsiella pneumoniae(n= 736), andAcinetobacter baumannii(n= 726) that had been collected from patients treated between 2008 and 2010 at 20 hospitals in Taiwan. MICs and inhibition zone diameters were interpreted according to the currently recommended U.S. Food and Drug Administration (FDA) criteria and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. The MIC90values of tigecycline against MRSA, VRE, ESBL-producingE. coli, ESBL-producingK. pneumoniae, andA. baumanniiwere 0.5, 0.125, 0.5, 2, and 8 μg/ml, respectively. The total error rates between the two methods using the FDA criteria were high: 38.4% for ESBL-producingK. pneumoniaeand 33.8% forA. baumannii. Using the EUCAST criteria, the total error rate was also high (54.6%) forA. baumanniiisolates. The total error rates between these two methods were <5% for MRSA, VRE, and ESBL-producingE. coli. For routine susceptibility testing of ESBL-producingK. pneumoniaeandA. baumanniiagainst tigecycline, the broth microdilution method should be used because of the poor correlation of results between these two methods.

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

2020 ◽  
Author(s):  
Romney Humphries ◽  
Shelley Campeau ◽  
Thomas E. Davis ◽  
Kristin J. Nagaro ◽  
Vincent J. LaBombardi ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Error Rate ◽  
Susceptibility Testing ◽  
Reference Method ◽  
Error Rates ◽  
Performance Criteria ◽  
Test Results ◽  
Major Error ◽  
Overall Performance ◽  
Vitek 2

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.

scholarly journals Clinical Validation of SensiTest Colistin, a Broth Microdilution-Based Method To Evaluate Colistin MICs

2018 ◽  
Vol 56 (4) ◽  
Author(s):  
Edoardo Carretto ◽  
Flavia Brovarone ◽  
Giuseppe Russello ◽  
Paola Nardini ◽  
Maisra M. El-Bouseary ◽  
...  
Keyword(s):  
Room Temperature ◽  
Susceptibility Testing ◽  
Reference Method ◽  
Multidrug Resistant ◽  
Clinical Validation ◽  
Gram Negative Bacteria ◽  
Broth Microdilution ◽  
Bacterial Strains ◽  
Global Spread ◽  
Severe Infections

ABSTRACT The global spread of multidrug-resistant Gram-negative bacteria has led to the return of colistin for treating severe infections. Recently, different plasmid-mediated genes conferring resistance to this drug were described and reported worldwide. International committees (EUCAST/CLSI) reevaluated inconsistencies surrounding colistin antimicrobial susceptibility testing (AST), concluding that broth microdilution (BMD) should serve as the reference method for AST. The development of an accurate, reproducible commercial test based on BMD is therefore highly desirable. SensiTest Colistin (STC), a BMD-based compact 4-test panel containing the lyophilized antibiotic in 7 2-fold dilutions (0.25 to 16 μg/ml) was here compared with the EUCAST-CLSI standard reference method (BMD) and, for some isolates, with the automated Phoenix 100 system (PHX). A total of 353 bacterial strains were evaluated by two different laboratories; 137 isolates were resistant to colistin (19 were intrinsically resistant, 83 harbored the mcr-1 gene). Essential agreement (EA) between STC and BMD was obtained for 339 out of the 353 strains tested (96.0%). Overall categorical agreement was obtained for 349 out of the 353 strains analyzed (98.9%). Two major errors (MEs; 0.93%) and two very major errors (VMEs; 1.46%) were documented. STC appeared to be a simple but highly reliable test with good reproducibility even with panels stored at room temperature or at 35°C. Moreover, STC showed a good performance with strains carrying the mcr-1 gene, with a 98.8% EA. As the secondary endpoint of our study, VMEs for PHX were documented for 6 isolates (10%).

scholarly journals Reappraisal of the antimicrobial susceptibilities of Chryseobacterium and Flavobacterium species and methods for reliable susceptibility testing.

1997 ◽  
Vol 41 (12) ◽  
pp. 2738-2741 ◽  
Author(s):  
S L Fraser ◽  
J H Jorgensen
Keyword(s):  
Susceptibility Testing ◽  
Opportunistic Infections ◽  
Clinical Laboratory ◽  
Error Rates ◽  
National Committee ◽  
Broth Microdilution ◽  
Gram Positive Bacteria ◽  
Serious Infections ◽  
Agar Dilution ◽  
Investigational Agents

Several Flavobacterium species, comprising a heterogeneous group of gram-negative bacilli that are capable of causing opportunistic infections in humans, have recently been reclassified as Chryseobacterium or Myroides species. Intrinsically resistant to a number of antibiotics, these organisms have been reported to be susceptible to vancomycin and certain other drugs that are normally active against gram-positive bacteria. By using the National Committee for Clinical Laboratory Standards (NCCLS) broth microdilution procedure, 58 clinical isolates of former flavobacteria (36 Chryseobacterium meningosepticum isolates, 11 C. indologenes isolates, 3 C. gleum isolates, 4 unspeciated former members of Flavobacterium group IIb, and 4 Myroides odoratum isolates) were tested with 23 antibiotics, including conventional and investigational agents. In addition, the broth microdilution results were compared to those generated by agar dilution, E-test, and disk diffusion for vancomycin and piperacillin-tazobactam. Compared to the NCCLS microdilution results, there were 7.1 and 17.9% very major errors with piperacillin-tazobactam by agar dilution and E-test, respectively. In addition, there were from 12.1 to 48.3% minor errors with both procedures with vancomycin and piperacillin-tazobactam. The very major and minor error rates were unacceptably high with disk testing of piperacillin-tazobactam; the use of enterococcal vancomycin disk breakpoints (zone diameter of > or =17 mm = susceptible) resulted in >20% minor errors but only one very major error. All of the isolates were susceptible to minocycline; over 90% were susceptible to sparfloxacin, levofloxacin, and clinafloxacin; and 88% were susceptible to rifampin. None was susceptible to vancomycin. When Chryseobacterium or Myroides species are isolated from serious infections, susceptibility testing by broth microdilution should be performed and therapy should be guided by those results.

scholarly journals Comparison of the Sensititre YeastOne and CLSI M38-A2 Microdilution Methods in Determining the Activity of Amphotericin B, Itraconazole, Voriconazole, and Posaconazole against Aspergillus Species

2018 ◽  
Vol 56 (10) ◽  
Author(s):  
Hsuan-Chen Wang ◽  
Ming-I Hsieh ◽  
Pui-Ching Choi ◽  
Chi-Jung Wu
Keyword(s):  
Aspergillus Fumigatus ◽  
Amphotericin B ◽  
Antifungal Agents ◽  
Susceptibility Testing ◽  
Geometric Mean ◽  
Antifungal Susceptibility ◽  
Reference Method ◽  
Aspergillus Species ◽  
Broth Microdilution ◽  
Content Type

ABSTRACT This study compared the YeastOne and reference CLSI M38-A2 broth microdilution methods for antifungal susceptibility testing of Aspergillus species. The MICs of antifungal agents were determined for 100 Aspergillus isolates, including 54 Aspergillus fumigatus (24 TR34/L98H isolates), 23 A. flavus, 13 A. terreus, and 10 A. niger isolates. The overall agreement (within 2 2-fold dilutions) between the two methods was 100%, 95%, 92%, and 90% for voriconazole, posaconazole, itraconazole, and amphotericin B, respectively. The voriconazole geometric mean (GM) MICs were nearly identical for all isolates using both methods, whereas the itraconazole and posaconazole GM MICs obtained using the YeastOne method were approximately 1 dilution lower than those obtained using the reference method. In contrast, the amphotericin B GM MIC obtained using the YeastOne method was 3.3-fold higher than that observed using the reference method. For the 24 A. fumigatus TR34/L98H isolates assayed, the categorical agreement (classified according to the CLSI epidemiological cutoff values) was 100%, 87.5%, and 83.3% for itraconazole, voriconazole, and posaconazole, respectively. For four A. niger isolates, the itraconazole MICs were >8 μg/ml using the M38-A2 method due to trailing growth, whereas the corresponding itraconazole MICs obtained using the YeastOne method were all ≤0.25 μg/ml without trailing growth. These data suggest that the YeastOne method can be used as an alternative for azole susceptibility testing of Aspergillus species and for detecting the A. fumigatus TR34/L98H isolates but that this method fails to detect A. niger isolates exhibiting trailing growth with itraconazole. Additionally, for isolates with azole MICs that approach or that are at susceptibility breakpoints or with high amphotericin B MICs detected using the YeastOne method, further MIC confirmation using the reference CLSI method is needed.

scholarly journals Heterogeneity of Macrolide-Lincosamide-Streptogramin B Resistance Phenotypes in Enterococci

2003 ◽  
Vol 47 (11) ◽  
pp. 3415-3420 ◽  
Author(s):  
Yu-Hong Min ◽  
Jae-Hee Jeong ◽  
Yun-Jeong Choi ◽  
Hee-Jeong Yun ◽  
Kyungwon Lee ◽  
...  
Keyword(s):  
Sequence Analysis ◽  
Enterococcus Faecalis ◽  
Reporter Gene ◽  
Enterococcus Faecium ◽  
Membered Ring ◽  
Macrolide Resistance ◽  
Clinical Isolates ◽  
Zone Of Inhibition ◽  
Regulatory Regions ◽  
Disk Test

ABSTRACT We determined the macrolide resistance phenotypes of 241 clinical isolates of erythromycin-resistant enterococci (MICs, ≥1 μg/ml), including 147 Enterococcus faecalis strains and 94 Enterococcus faecium strains, collected from a hospital in Seoul, Korea, between 1999 and 2000. By the erythromycin (40 μg)-josamycin (100 μg) double-disk test, 93 strains were assigned to the constitutive macrolide, lincosamide, and streptogramin B (MLSB) resistance (cMLSB) phenotype, and the remaining 148 strains were assigned to the inducible MLSB resistance (iMLSB) phenotype. Of the strains with the iMLSB phenotype, 36 exhibited a reversibly inducible MLSB (riMLSB) phenotype, i.e., blunting of the erythromycin zone of inhibition, which indicates that the 16-membered-ring macrolide josamycin is a more effective inducer than the 14-membered-ring macrolide erythromycin. Sequence analysis of the regulatory regions of the erm(B) genes from all of the strains exhibiting the riMLSB phenotype revealed not only erm(Bv) [where v represents variant; previously erm(AMR)] (n = 13), as reported previously, but also three kinds of erm(B) variants, which were designated erm(Bv1) (n = 17), erm(Bv2) (n = 3), and erm(Bv3) (n = 3), respectively. In lacZ reporter gene assays of these variants, the 16-membered-ring macrolide tylosin had stronger inducibility than erythromycin at ≥0.1 μg/ml. These findings highlight the versatility of erm(B) in induction specificity.

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