Performance Accuracy of Antibacterial and Antifungal Susceptibility Test Methods: Report From the College of American Pathologists Microbiology Surveys Program (2001–2003)

2006 ◽  
Vol 130 (6) ◽  
pp. 767-778 ◽  
Author(s):  
Michael A. Pfaller ◽  
Ronald N. Jones
Keyword(s):  
Antifungal Susceptibility ◽  
Test Methods ◽  
Disk Diffusion ◽  
Test Accuracy ◽  
Broth Microdilution ◽  
Coagulase Negative Staphylococci ◽  
Disk Diffusion Test ◽  
Gram Negative ◽  
Antibacterial Test ◽  
Susceptibility Tests

Abstract Context.—The College of American Pathologists Microbiology Surveys Program provides external proficiency samples that monitor the performance of nearly 3000 laboratories that perform and report antimicrobial susceptibility tests. Objective.—To summarize results obtained with bacterial and yeast challenge samples (2001 through 2003). Design.—One organism every 4 months was tested by surveys participants against antibacterials/antifungals by routinely used methods. Reports were graded by interpretive category (susceptible, intermediate, resistant) based on an 80% consensus of referees/participants. Results.—The most common antibacterial test methods/ systems were Vitek (38%–43%), MicroScan (39%–43%), and the disk diffusion test (14%–15%), although Etest was most used for fastidious species. YeastOne was the dominant antifungal test (50%–55%). Antifungal results demonstrated continuous, improved accuracy (83%–88%), highest for YeastOne (96%) and broth microdilution (95%) methods. Antibacterial test accuracy was consistently greater than 97% against gram-positive organism challenges and greater than 98% against gram-negative challenges. For gram-negative strains with well-characterized resistance mechanisms, the accuracy by method was disk diffusion greater than broth microdilution greater than automated systems. Major problems identified were (1) Haemophilus influenzae control ranges require re-evaluation, (2) overuse of β-lactamase tests, (3) errors among Enterococcus faecium against penicillins (Vitek 2, MicroScan), (4) false-susceptible results with trimethoprim/sulfamethoxazole against coagulase-negative staphylococci (MicroScan), (5) macrolide false-susceptibility for β-hemolytic streptococcus (MicroScan), (6) flawed reporting for antimicrobials not active at the infection site, (7) use of outdated interpretive criteria, and (8) failure to follow Clinical and Laboratory Standards Institute testing/reporting recommendations. Conclusions.—Susceptibility tests were generally performing satisfactorily as measured by the surveys, but serious errors were identified with some drug/organism combinations that may require action by the Clinical and Laboratory Standards Institute and/or the Food and Drug Administration.

scholarly journals Beta-lactamases and detection of beta-lactam resistance in Enterobacter spp.

1997 ◽  
Vol 41 (1) ◽  
pp. 35-39 ◽  
Author(s):  
J D Pitout ◽  
E S Moland ◽  
C C Sanders ◽  
K S Thomson ◽  
S R Fitzsimmons
Keyword(s):  
Disk Diffusion ◽  
Broth Microdilution ◽  
Beta Lactam ◽  
Disk Diffusion Test ◽  
Beta Lactamases ◽  
Beta Lactam Antibiotics ◽  
Resistant Strains ◽  
Group 2 ◽  
Susceptibility Tests ◽  
Group 1

Enterobacter spp. are becoming increasingly frequent nosocomial pathogens, and beta-lactam-resistant strains are on the increase, especially among isolates recovered from intensive care units. Therefore, a study was designed to characterize the beta-lactamases produced by 80 isolates of E. cloacae, E. aerogenes, E. taylorae, E. gergoviae, E. sakazakii, E. asburiae, and E. agglomerans by induction studies, spectrophotometric hydrolysis assays, and isoelectric focusing. The ability of broth microdilution and disk diffusion susceptibility tests to detect resistance to 16 beta-lactam antibiotics among these species was also assessed. All species except E. agglomerans, E. gergoviae, and some isolates of E. sakazakii were found to produce a Bush group 1 cephalosporinase that was expressed inducibly or constitutively at high levels. In addition, some strains also produced a Bush group 2 beta-lactamase. In comparisons of broth microdilution and disk diffusion tests, disk diffusion tests failed to detect resistance in 1 of 25 isolates resistant to aztreonam and 2 of 30 isolates resistant to ceftazidime. These results indicate that species of Enterobacter can possess a variety of beta-lactamases that are responsible for beta-lactam resistance in this genus and that the disk diffusion test may occasionally miss resistance in some strains.

scholarly journals Variation in erythromycin and clindamycin susceptibilities of Streptococcus pneumoniae by four test methods.

1997 ◽  
Vol 41 (1) ◽  
pp. 129-134 ◽  
Author(s):  
E L Fasola ◽  
S Bajaksouzian ◽  
P C Appelbaum ◽  
M R Jacobs
Keyword(s):  
Streptococcus Pneumoniae ◽  
Susceptibility Testing ◽  
Ambient Air ◽  
Test Methods ◽  
Disk Diffusion ◽  
Broth Microdilution ◽  
Microdilution Method ◽  
Broth Microdilution Method ◽  
Agar Dilution ◽  
Resistant Strains

Susceptibilities of 124 strains of Streptococcus pneumoniae to erythromycin and clindamycin were determined by the National Committee for the Clinical Laboratory Standards (NCCLS) broth microdilution method, with incubation for 20 to 24 h in ambient air and with modifications of this method by incubation for up to 48 h in air and CO2. Strains were also tested by agar dilution, E-test, and disk diffusion; good correlation was obtained with these methods, with clear separation into bimodal populations of susceptible and resistant stains. The broth microdilution method, however, using incubation in air for 24 h (NCCLS method), misclassified 4 of 92 erythromycin-resistant strains (1 as susceptible and 3 as intermediate) and 25 of 58 clindamycin-resistant strains (all as susceptible). With the exception of one strain with clindamycin, susceptible and resistant strains were correctly classified by the microdilution method with incubation in CO2 for 24 h or in ambient air for 48 h. Disk diffusion, agar dilution, and E-test methods with incubation in 5% CO2 are therefore reliable methods for susceptibility testing of pneumococci against these agents. However, the NCCLS microdilution method, which specifies incubation for 20 to 24 h in ambient air, produced significant very major errors (43%) clindamycin. Modification of the microdilution method by incubation in 5% CO2 or by extension of incubation time in ambient air to 48 h corrected these errors. Disk diffusion, however, was shown to be a simple, convenient, and reliable method for susceptibility testing of pneumococci to erythromycin and clindamycin and is suggested as the method of choice for these agents.

scholarly journals Quality Control Limits for Dilution and Disk Diffusion Susceptibility Tests of Trovafloxacin against Eight Quality Control Strains

1998 ◽  
Vol 36 (2) ◽  
pp. 585-586
Author(s):  
Peter C. Fuchs ◽  
Arthur L. Barry ◽  
Steven D. Brown
Keyword(s):  
Quality Control ◽  
Disk Diffusion ◽  
Collaborative Effort ◽  
Broth Microdilution ◽  
Agar Dilution ◽  
Susceptibility Tests ◽  
And Control ◽  
Control Limits

A 10-laboratory collaborative effort was designed to generate data to propose quality control limits for susceptibility tests of trovafloxacin. Broth microdilution, agar dilution, and disk diffusion tests were evaluated with eight different control strains. All tests were reproducible, and control limits are proposed.

scholarly journals Methods for Improved Detection of Oxacillin Resistance in Coagulase-Negative Staphylococci: Results of a Multicenter Study

1999 ◽  
Vol 37 (12) ◽  
pp. 4051-4058 ◽  
Author(s):  
Fred C. Tenover ◽  
Ronald N. Jones ◽  
Jana M. Swenson ◽  
Barbara Zimmer ◽  
Sigrid McAllister ◽  
...  
Keyword(s):  
Clinical Laboratory ◽  
Reference Method ◽  
Disk Diffusion ◽  
National Committee ◽  
Broth Microdilution ◽  
Pcr Assay ◽  
Coagulase Negative Staphylococci ◽  
Oxacillin Resistance ◽  
Disk Diffusion Testing ◽  
Single Disk

A multilaboratory study was undertaken to determine the accuracy of the current National Committee for Clinical Laboratory Standards (NCCLS) oxacillin breakpoints for broth microdilution and disk diffusion testing of coagulase-negative staphylococci (CoNS) by using a PCR assay for mecA as the reference method. Fifty well-characterized strains of CoNS were tested for oxacillin susceptibility by the NCCLS broth microdilution and disk diffusion procedures in 11 laboratories. In addition, organisms were inoculated onto a pair of commercially prepared oxacillin agar screen plates containing 6 μg of oxacillin per ml and 4% NaCl. The results of this study and of several other published reports suggest that, in order to reliably detect the presence of resistance mediated bymecA, the oxacillin MIC breakpoint for defining resistance in CoNS should be lowered from ≥4 to ≥0.5 μg/ml and the breakpoint for susceptibility should be lowered from ≤2 to ≤0.25 μg/ml. In addition, a single disk diffusion breakpoint of ≤17 mm for resistance and ≥18 mm for susceptibility is suggested. Due to the poor sensitivity of the oxacillin agar screen plate for predicting resistance in this study, this test can no longer be recommended for use with CoNS. The proposed interpretive criteria for testing CoNS have been adopted by the NCCLS.

scholarly journals Cefiderocol Antimicrobial Susceptibility Testing against Multidrug-Resistant Gram-Negative Bacilli: a Comparison of Disk Diffusion to Broth Microdilution

2020 ◽  
Vol 59 (1) ◽  
pp. e01649-20 ◽  
Author(s):  
C. Paul Morris ◽  
Yehudit Bergman ◽  
Tsigedera Tekle ◽  
John A. Fissel ◽  
Pranita D. Tamma ◽  
...  
Keyword(s):  
Antimicrobial Susceptibility ◽  
Susceptibility Testing ◽  
Multidrug Resistant ◽  
Antimicrobial Susceptibility Testing ◽  
Disk Diffusion ◽  
Broth Microdilution ◽  
Gram Negative ◽  
Content Type ◽  
Carbapenem Resistant ◽  
Alternative Approach

ABSTRACTAntimicrobial susceptibility testing (AST) of cefiderocol poses challenges because of its unique mechanism of action (i.e., requiring an iron-depleted state) and due to differences in interpretative criteria established by the Clinical and Laboratory Standards Institute (CLSI), U.S. Food and Drug Administration (FDA), and European Committee on Antimicrobial Susceptibility Testing (EUCAST). Our objective was to compare cefiderocol disk diffusion methods (DD) to broth microdilution (BMD) for AST of Gram-negative bacilli (GNB). Cefiderocol AST was performed on consecutive carbapenem-resistant Enterobacterales (CRE; 58 isolates) and non-glucose-fermenting GNB (50 isolates) by BMD (lyophilized panels; Sensititre; Thermo Fisher) and DD (30 μg; research-use-only [RUO] MASTDISCS and FDA-cleared HardyDisks). Results were interpreted using FDA (prior to 28 September 2020 update), EUCAST, and investigational CLSI breakpoints (BPs). Categorical agreement (CA), minor errors (mE), major errors (ME), and very major errors (VME) were calculated for DD methods. The susceptibilities of all isolates by BMD were 72% (FDA), 75% (EUCAST) and 90% (CLSI). For DD methods, EUCAST BPs demonstrated lower susceptibility at 65% and 66%, compared to 74% and 72% (FDA) and 87% and 89% (CLSI) by HardyDisks and MASTDISCS, respectively. CA ranged from 75% to 90%, with 8 to 25% mE, 0 to 19% ME, and 0 to 20% VME and varied based on disk, GNB, and BPs evaluated. Both DD methods performed poorly for Acinetobacter baumannii complex. There is considerable variability when cefiderocol ASTs are interpreted using CLSI, FDA, and EUCAST breakpoints. DD offers a convenient alternative approach to BMD methods for cefiderocol AST, with the exception of A. baumannii complex isolates.

Quality control limits for disk diffusion and broth microdilution susceptibility tests with Haemophilus test medium

1991 ◽  
Vol 14 (6) ◽  
pp. 485-493 ◽  
Author(s):  
Gary V. Doern ◽  
E.Hugh Gerlach ◽  
James H. Jorgensen ◽  
Patrick R. Murray ◽  
Clyde Thornsberry ◽  
...  
Keyword(s):  
Quality Control ◽  
Disk Diffusion ◽  
Broth Microdilution ◽  
Test Medium ◽  
Susceptibility Tests ◽  
Control Limits
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