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Ana C Gales - One of the best experts on this subject based on the ideXlab platform.
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in vitro susceptibility of burkholderia cepacia complex isolates comparison of disk diffusion etest Agar Dilution and broth microDilution methods
Diagnostic Microbiology and Infectious Disease, 2016Co-Authors: Lorena Cristina Correa Fehlberg, Adriana Gianinni Nicoletti, Ana Ramos, Fernanda Rodriguescosta, Adriana Pereira Matos, Raquel Girardello, Elizabeth Andrade Marques, Ana C GalesAbstract:Broth microDilution, Agar Dilution, Etest® and disk diffusion techniques were compared to evaluate the susceptibility profile of 82 Bcc clinical isolates against six antimicrobials as recommended by CLSI. Broth microDilution was considered the "gold standard" method. The regression analysis was applied to determine the essential (EA) and categorical (CA) agreement rates. STX (MIC50, 1 mg/L) was the most potent antimicrobial tested against Bcc isolates. The worst in vitro activity was observed for chloramphenicol (MIC50, 16 mg/L) and ticarcillin-clavulanic acid (MIC50, >256 mg/L). The EA among broth microDilution and Agar Dilution results was good for the majority of antimicrobial tested. When comparing broth microDilution and Etest®, ceftazidime, SXT and chloramphenicol exhibited EA rates below 90%. SXT showed an excellent CA (100%) when Dilution methodologies were compared. However, a low CA rate was found for this agent between Dilution and disk diffusion methodologies resulting in unacceptable very major and minor error rates.
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antimicrobial susceptibility testing for helicobacter pylori isolates from brazilian children and adolescents comparing Agar Dilution e test and disk diffusion
Brazilian Journal of Microbiology, 2014Co-Authors: Silvio Kazuo Ogata, Ana C Gales, Elisabete KawakamiAbstract:Antimicrobial susceptibility testing for Helicobacter pylori is increasingly important due to resistance to the most used antimicrobials agents. Only Agar Dilution method is approved by CLSI, but it is difficult to perform routinely. We evaluated the reliability of E-test and disk diffusion comparing to Agar Dilution method on Helicobacter pylori antimicrobial susceptibility testing. Susceptibility testing was performed for amoxicillin, clarithromycin, furazolidone, metronidazole and tetracycline using E-test, disk-diffusion and Agar Dilution method in 77 consecutive Helicobacter pylori strains from dyspeptic children and adolescents. Resistance rates were: amoxicillin - 10.4%, 9% and 68.8%; clarithromycin - 19.5%, 20.8%, 36.3%; metronidazole - 40.2%33.7%, 38.9%, respectively by Agar Dilution, E-test and disk diffusion method. Furazolidone and tetracycline showed no resistance rates. Metronidazole presented strong correlation to E-test (r = 0.7992, p < 0.0001) and disk diffusion method (r=-0.6962, p < 0.0001). Clarithromycin presented moderate correlation to E-test (r = 0.6369, p < 0.0001) and disk diffusion method (r=-0.5656, p < 0.0001). Amoxicillin presented weak correlation to E-test (r = 0.3565, p = 0.0015) and disk diffusion (r=-0.3565, p = 0.0015). Tetracycline presented weak correlation with E-test (r = 0.2346, p = 0.04) and furazolidone to disk diffusion (r=-0.0288, p = 0.8038). E-test presented better agreement with gold standard. It is an easy and reliable method for Helicobacter pylori susceptibility testing. Disk diffusion method presented high disagreement and high rates of major errors.
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comparison of m i c e and etest with clsi Agar Dilution for antimicrobial susceptibility testing against oxacillin resistant staphylococcus spp
PLOS ONE, 2014Co-Authors: Eloiza H Campana, Cecilia G Carvalhaes, Bruna Nonato, Antonia M O Machado, Ana C GalesAbstract:Objective The main objective of this study was to comparatively evaluate the performance of M.I.C.E. and Etest methodologies to that of Agar Dilution for determining the antimicrobial susceptibility profile of oxacillin-resistant Staphylococcus spp. Methods A total of 100 oxacillin-resistant Staphylococcus spp. isolates were collected from hospitalized patients at a teaching hospital. Antimicrobial susceptibility testing for vancomycin, teicoplanin and linezolid was performed using the reference CLSI Agar Dilution method (2009), Etest and M.I.C.E. methodologies. The MIC values were interpreted according to CLSI susceptibility breakpoints and compared by regression analysis. Results In general, the essential agreement (±1-log2) between M.I.C.E. and CLSI Agar Dilution was 93.0%, 84.0% and 77.0% for linezolid, teicoplanin and vancomycin, respectively. Essential agreement rates between M.I.C.E. and Etest were excellent (>90.0%) for all antibiotics tested. Both strips (M.I.C.E. and Etest) yielded two very major errors for linezolid. Unacceptable minor rates were observed for teicoplanin against CoNS and for vancomycin against S. aureus. Conclusions According to our results, linezolid and teicoplanin MICs against all staphylococci and S. aureus, respectively, were more accurately predicted by M.I.C.E. strips. However, the Etest showed better performance than M.I.C.E. for predicting vancomycin MICs against all staphylococci. Thus, microbiologists must be aware of the different performance of commercially available gradient strips against staphylococci.
Peter C Appelbaum - One of the best experts on this subject based on the ideXlab platform.
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activity of retapamulin against streptococcus pyogenes and staphylococcus aureus evaluated by Agar Dilution microDilution e test and disk diffusion methodologies
Antimicrobial Agents and Chemotherapy, 2006Co-Authors: Glenn A Pankuch, Michael R Jacobs, Gengrong Lin, Dianne B Hoellman, Caryn E Good, Peter C AppelbaumAbstract:The in vitro activity of retapamulin against 106 Staphylococcus aureus isolates and 109 Streptococcus pyogenes isolates was evaluated by the Agar Dilution, broth microDilution, E-test, and disk diffusion methodologies. Where possible, the tests were performed by using the CLSI methodology. The results of Agar Dilution, broth microDilution, and E-test (all with incubation in ambient air) for S. aureus yielded similar MICs, in the range of 0.03 to 0.25 μg/ml. These values corresponded to zone diameters between 25 and 33 mm by the use of a 2-μg retapamulin disk. Overall, 99% of the Agar Dilution results and 95% of E-test results for S. aureus were within ±1 Dilution of the microDilution results. For S. pyogenes , the MICs obtained by the Agar and broth microDilution methods (both after incubation in ambient air) were in the range of 0.008 to 0.03 μg/ml, and E-test MICs (with incubation in ambient air) were 0.016 to 0.06 μg/ml. For S. pyogenes , 100% of the Agar Dilution MIC results were within ±1 Dilution of the broth microDilution results. E-test MICs (after incubation in ambient air) were within ±1 and ±2 Dilutions of the broth microDilution results for 76% and 99% of the isolates, respectively. E-test MICs for S. pyogenes strains in CO 2 were up to 4 Dilutions higher than those in ambient air. Therefore, it is recommended that when retapamulin MICs are determined by E-test, incubation be done in ambient air and not in CO 2 , due to the adverse effect of CO 2 on the activity of this compound. Diffusion zones (with incubation in CO 2 ) for S. pyogenes were 18 to 24 mm. Retapamulin MICs for all strains by all methods (with incubation in ambient air) were ≤0.25 μg/ml. These results demonstrate that S. pyogenes (including macrolide-resistant strains) and S. aureus (including methicillin-resistant and vancomycin-nonsusceptible strains) are inhibited by very low concentrations of retapamulin and that all four testing methods are satisfactory for use for susceptibility testing.
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antipneumococcal activity of telithromycin by Agar Dilution microDilution e test and disk diffusion methodologies
Journal of Clinical Microbiology, 2000Co-Authors: Todd A Davies, Michael R Jacobs, Linda M Kelly, Peter C AppelbaumAbstract:Agar Dilution and microDilution (both in air) and E test and disk diffusion (both in air and CO2) were used to test the activity of telithromycin against 110 erythromycin-susceptible and 106 erythromycin-resistant pneumococci. The MICs at which 50 and 90% of strains are inhibited (MIC50s and MIC90s, respectively) for erythromycin-susceptible strains varied between 0.008 and 0.016 μg/ml and 0.016 and 0.03 μg/ml when the samples were incubated in air. By comparison, telithromycin MIC50s and MIC90s for erythromycin-resistant strains were in air 0.03 to 0.125 and 0.125 to 0.5 μg/ml, respectively. When Agar Dilution was used as the reference method, essential agreement was found for 112 of 216 strains (51.9%) for microDilution, 168 of 216 (77.8%) for E test in air, and 132 of 216 (61.1%) for E test in CO2. With the exception of four strains tested by E test in CO2, all organisms were susceptible to a proposed telithromycin susceptibility breakpoint of ≤1 μg/ml. By disk diffusion with 15-μg telithromycin disks, all strains but one had zones of inhibition ≥19 mm in diameter when incubated in CO2, while all strains had zone diameters of ≥22 mm when incubated in air. Zone diameters in air were generally 4 to 5 mm larger than in CO2. By all methods, MICs and zones of all erythromycin-resistant strains occurred in clusters separated from those seen with erythromycin-susceptible strains. The results for macrolide-resistant strains with erm and mef resistance determinants were similar. The results show that (i) telithromycin is very active against erythromycin-susceptible and -resistant strains irrespective of macrolide resistance mechanism; (ii) susceptibility to telithromycin can be reliably tested by the Agar, microDilution, E test, and disk diffusion methods; and (iii) incubation in CO2 led to smaller zones by disk diffusion and higher MICs by E test, but at a susceptible MIC breakpoint of ≤1 μg/ml and a susceptible zone diameter cutoff of ≥19 mm in CO2, 215 of 216 strains were found to be susceptible to telithromycin.
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antipneumococcal activities of levofloxacin and clarithromycin as determined by Agar Dilution microDilution e test and disk diffusion methodologies
Journal of Clinical Microbiology, 1998Co-Authors: Catherine Clark, Michael R Jacobs, Peter C AppelbaumAbstract:The activities of levofloxacin and clarithromycin against 199 penicillin- and macrolide-susceptible and -resistant pneumococci were tested by Agar and microDilution methods in air and by disk diffusion and E-test methods in air and CO 2 . For levofloxacin, ≥99.0% of strains were susceptible at ≤2.0 μg/ml with zone diameters of ≥17 mm, regardless of incubation in air or CO 2 . Although zone sizes were smaller and E-test MICs were higher for clarithromycin in CO 2 than those in air, category differences were minor, and susceptibility rates for clarithromycin were similar to those obtained by Agar and microDilution in air (range, 76.9 to 80.9% by all methods). For clarithromycin, adjustment of breakpoints based upon distribution of results resulted in susceptibility rates which were similar by all methods (75.8 to 76.9% susceptible, 0 to 1.5% intermediate, 22.6 to 23.1% resistant). Minor discrepancies were obtained with levofloxacin for one strain (0.5%) by microDilution and two strains (1.0%) by disk diffusion in CO 2 . For clarithromycin, minor discrepancies were found in three strains (1.5%) by microDilution, seven strains (3.5%) by Agar Dilution, four strains (2.0%) by E-test in air, six strains (3.0%) by disk diffusion in air, and five strains (2.5%) by disk diffusion in CO 2 . Major discrepancies occurred with levofloxacin in one strain (0.5%) by microDilution but were not found with clarithromycin. Very major discrepancies were not seen with levofloxacin, but occurred with clarithromycin in five strains (2.5%) by microDilution, three strains (1.5%) by Agar Dilution, two strains (1.0%) by E-test in air, eight strains (4.0%) by disk diffusion in air, and one strain (0.5%) by disk diffusion in CO 2 .
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activities of beta lactams against acinetobacter genospecies as determined by Agar Dilution and e test mic methods
Antimicrobial Agents and Chemotherapy, 1997Co-Authors: Melissa A Visalli, M R Jacobs, T D Moore, F A Renzi, Peter C AppelbaumAbstract:The Agar Dilution MIC method was used to test activities of ticarcillin, ticarcillin-clavulanate, amoxicillin, amoxicillin-clavulanate, ampicillin, ampicillin-sulbactam, piperacillin, piperacillin-tazobactam, inhibitors alone, ceftazidime, and imipenem against 237 Acinetobacter genospecies. A total of 93.2% of strains were beta-lactamase positive by the chromogenic cephalosporin method. Overall, ampicillin-sulbactam was the most active combination against all strains (MIC at which 50% of the isolates are inhibited [MIC50] and MIC90, 4.0 and 32.0 microg/ml; 86.9% susceptible at < or = 16 microg/ml), followed by ticarcillin-clavulanate (16.0 and 128.0 microg/ml; 85.7% susceptible at < or = 64 microg/ml), piperacillin-tazobactam (16.0 and 128.0 microg/ml; 84.8% susceptible at < or = 64 microg/ml), and amoxicillin-clavulanate (16.0 and 64.0 microg/ml; 54.4% susceptible at < or =16 microg/ml). Ceftazidime and imipenem yielded MIC50s and MIC90s of 8.0 and 64.0 microg/ml (ceftazidime) and 0.5 and 1.0 microg/ml (imipenem), respectively; 71.3% of strains were susceptible to ceftazidime at < or = 16 microg/ml, and 99.2% were susceptible to imipenem at < or = 8 microg/ml. Sulbactam was the most active beta-lactamase inhibitor alone (MIC50 and MIC90, 2.0 and 16.0 microg/ml); clavulanate and tazobactam were less active (16.0 and 32.0 microg/ml for both compounds). Enhancement of beta-lactams by beta-lactamase inhibitors was not always seen in beta-lactamase-positive strains, and activity of combinations such as ampicillin-sulbactam was due to the inhibitor alone. Acinetobacter baumannii was the most resistant genospecies. By contrast, Acinetobacter haemolyticus, Acinetobacter calcoaceticus, Acinetobacter johnsonii, Acinetobacter junii, Acinetobacter radioresistens, and other non-Acinetobacter baumannii strains were more susceptible to all compounds tested. E-test MICs were within 1 Dilution of Agar Dilution MICs in 38.4 to 89.6% of cases and within 2 Dilutions in 61.6 to 98.6% of cases.
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susceptibilities of 201 anaerobes to erythromycin azithromycin clarithromycin and roxithromycin by oxyrase Agar Dilution and e test methodologies
Journal of Clinical Microbiology, 1995Co-Authors: S K Spangler, M R Jacobs, Peter C AppelbaumAbstract:The susceptibility of 201 anaerobes to erythromycin, azithromycin, clarithromycin, and roxithromycin was tested by Agar Dilution and E test methods by using a commercially available plate and dish system (OxyDish) to provide anaerobic conditions. Plates were incubated for 48 h. MICs for 50% of strains tested and MICs for 90% of strains tested by Agar Dilution and E test methods corresponded within 1 doubling Dilution for all compounds. When all antibiotics were considered together, Agar and E test MICs were within 1 and 2 doubling Dilutions of each other in 84 to 91% and > 99% of cases, respectively.
Ronald N Jones - One of the best experts on this subject based on the ideXlab platform.
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anti gonococcal activity of gemifloxacin against fluoroquinolone resistant strains and a comparison of Agar Dilution and etest methods
Journal of Antimicrobial Chemotherapy, 2000Co-Authors: Ronald N Jones, Mary S Barrett, Lalitagauri M Deshpande, Meredith E Erwin, Mondell L BeachAbstract:Gemifloxacin is a novel quinolone with excellent activity against Gram-positive and some Gram-negative pathogens. Its activity was tested against 150 Neisseria gonorrhoeae strains, including 50 ciprofloxacin-resistant isolates, using reference Agar Dilution and Etest methods. Gemifloxacin was found to be highly potent against ciprofloxacin-susceptible strains (MIC(90) 0.008 mg/L), but was 16-fold less potent against ciprofloxacin-resistant gonococci. The order of quinolone potency against these fluoroquinolone-resistant mutants was: gemifloxacin (MIC(90) 0.12 mg/L) > trovafloxacin (0.25 mg/L) > moxifloxacin = grepafloxacin (0.5 mg/L) > ciprofloxacin (1 mg/L). Etest and reference Agar Dilution MIC results showed excellent correlation (r = 0.96) and >98% of MICs were within +/-1 log(2) Dilution step (essential agreement). The excellent potency of gemifloxacin indicates its potential for the treatment of infections with quinolone-resistant N. gonorrhoeae.
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medium and supplement effects on the antimicrobial activity of quinupristin dalfopristin tested by Agar Dilution and etest methods
Diagnostic Microbiology and Infectious Disease, 1996Co-Authors: Ronald N JonesAbstract:Abstract Quinupristin/dalfopristin (also known as RP-59500 and Synercid), a streptogramin combination has been documented as active against a wide variety of Gram-positive species. Broad ranges of MIC results have been observed with some species using acceptable susceptibility testing methods. To address the contribution of testing medium and supplements to this disagreement, 15 medium or supplement alterations were studied in a reference Agar Dilution format and three variations of Mueller-Hinton Agar were used for Etest (AB Biodisk, Solna, Sweden). One-third of the Agar Dilution variations produced a consistent elevation (twofold) in the quinupristin/dalfopristin MIC. The greatest changes were secondary to additions of serum and blood, pH increases, and possibly charcoal. Similarly, the Etest MICs for quinupristin/dalfopristin were 0.5 to 2.5 log 2 Dilutions higher with media supplemented with 5% sheep erythrocytes or when chocolated. Additional quinupristin/dalfopristin stability experiments in three Agars indicate a two- to fourfold decline in potency over 21 days of storage at 2 to 5°C. These variations in the streptogramin MIC results would be observed most frequently when testing fastidious species or in laboratories routinely testing all Gram-positive bacteria in or on blood-supplemented media.
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evaluation of in vitro spectra of activity of azithromycin clarithromycin and erythromycin tested against strains of neisseria gonorrhoeae by reference Agar Dilution disk diffusion and etest methods
Journal of Clinical Microbiology, 1996Co-Authors: P C Mehaffey, S D Putnam, Mary S Barrett, Ronald N JonesAbstract:The macrolide-azilide susceptibility testing (Agar Dilution, disk diffusion, Etest) criteria for 105 Neisseria gonorrhoeae strains were evaluated. In addition, the potencies of azithromycin, clarithromycin, and erythromycin were studied. The most active macrolide-azilide agent was azithromycin (MIC at which 90% of the isolates are inhibited [MIC90], 0.5 microgram/ml) compared with clarithromycin (MIC90, 1.5 to 2 micrograms/ml) and erythromycin (MIC90, 2 to 4 micrograms/ml). The Etest (AB Biodisk, Solna, Sweden) was observed to produce MIC results very similar to those of the reference Agar Dilution test (GC Agar base), with 100% of the results within 1 log2 Dilution step of the reference MICs. The disk diffusion test zone diameters for all three drugs correlated at an acceptable level (r = -0.81 to -0.92) with the reference Agar Dilution MICs. Interpretive criteria for susceptibility were proposed for azithromycin at a MIC of or = 25 mm. No category for resistance was proposed because of the paucity of strains for which MICs were > 2 micrograms/ml. These tentative criteria should be further validated by correlations with clinical trial data for gonococcal strains (as they emerge) that have azithromycin MICs above the proposed susceptible category range.
Huguette Gilbert - One of the best experts on this subject based on the ideXlab platform.
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comparison of disc diffusion and Agar Dilution methods for antibiotic susceptibility testing of campylobacter jejuni subsp jejuni and campylobacter coli
Journal of Antimicrobial Chemotherapy, 1997Co-Authors: Christiane Gaudreau, Huguette GilbertAbstract:: The correlation between disc diffusion and Agar Dilution susceptibility testing of five antibiotics was studied against 145 Campylobacter strains: 99 Campylobacter jejuni subsp. jejuni and 46 Campylobacter coli. The percentages of true results and 95% CI for disc diffusion for resistant strains were 100% (93.2-100%) for tetracycline (53 strains tested), 100% (77.2-100%) for ciprofloxacin (13 strains tested), 86.7% (62.1-96.3%) for nalidixic acid (15 strains tested), 100% (56.6-100%) for erythromycin (five strains tested) and 68.8% (44.4-85.8%) for ampicillin (16 strains tested). The percentages of true results and 95% CI were 97.6-100% and 93.2-100% respectively for 89-140 susceptible strains to the five antibiotics tested. There was a 1.4% major error for nalidixic acid, 0.7% very major error for erythromycin, 5.5% and 1.4% minor and major errors respectively for ampicillin. There was complete agreement for ciprofloxacin and tetracycline. Results of ampicillin susceptibility are not expected to be useful in a clinical setting. The nalidixic acid disc is a marker of ciprofloxacin susceptibility as the nalidixic acid-susceptible strains were susceptible to ciprofloxacin while most of the resistant ones were resistant to ciprofloxacin. Overall, our results suggest that disc diffusion is a reliable, easy and inexpensive susceptibility testing method for C. jejuni and C. coli for erythromycin, ciprofloxacin and tetracycline. Until more erythromycin- and ciprofloxacin-resistant strains are tested to confirm the reliability of this test, the resistance to these drugs needs to be confirmed using the Etest or the Agar Dilution method.
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comparison of disc diffusion and Agar Dilution methods for antibiotic susceptibility testing of campylobacter jejuni subsp jejuni and campylobacter coli
Journal of Antimicrobial Chemotherapy, 1997Co-Authors: Christiane Gaudreau, Huguette GilbertAbstract:The correlation between disc diffusion and Agar Dilution susceptibility testing of five antibiotics was studied against 145 Campylobacter strains: 99 Campylobacter jejuni subsp. jejuni and 46 Campylobacter coli. The percentages of true results and 95% CI for disc diffusion for resistant strains were 100% (93.2‐100%) for tetracycline (53 strains tested), 100% (77.2‐100%) for ciprofloxacin (13 strains tested), 86.7% (62.1‐96.3%) for nalidixic acid (15 strains tested), 100% (56.6‐100%) for erythromycin (five strains tested) and 68.8% (44.4‐ 85.8%) for ampicillin (16 strains tested). The percentages of true results and 95% CI were 97.6‐100% and 93.2‐100% respectively for 89‐140 susceptible strains to the five antibiotics tested. There was a 1.4% major error for nalidixic acid, 0.7% very major error for erythromycin, 5.5% and 1.4% minor and major errors respectively for ampicillin. There was complete agreement for ciprofloxacin and tetracycline. Results of ampicillin susceptibility are not expected to be useful in a clinical setting. The nalidixic acid disc is a marker of ciprofloxacin susceptibility as the nalidixic acid-susceptible strains were susceptible to ciprofloxacin while most of the resistant ones were resistant to ciprofloxacin . Overall, our results suggest that disc diffusion is a reliable, easy and inexpensive susceptibility testing method for C. jejuni and C. coli for erythromycin, ciprofloxacin and tetracycline. Until more erythromycin- and ciprofloxacin-resistant strains are tested to confirm the reliability of this test, the resistance to these drugs needs to be confirmed using the Etest or the Agar Dilution method.
Clyde Thornsberry - One of the best experts on this subject based on the ideXlab platform.
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comparison of the e test to Agar Dilution broth microDilution and Agar diffusion susceptibility testing techniques by using a special challenge set of bacteria
Journal of Clinical Microbiology, 1991Co-Authors: C N Baker, Sheila A Stocker, D H Culver, Clyde ThornsberryAbstract:The E Test (AB Biodisk, Solna, Sweden) is a new method for performing antimicrobial susceptibility tests. It consists of an impervious carrier (5- by 50-mm strip) with a predefined antimicrobic gradient which is placed on an inoculated Agar plate and processed like a disk diffusion test. Results are generated directly as MICs from a continuous concentration gradient covering 15 twofold Dilutions, and MICs are read where the edge of the inhibition zone intersects the strip. We compared the E Test with disk diffusion, broth microDilution, and Agar Dilution tests by using a challenge set of 195 gram-positive and gram-negative bacteria for 14 antimicrobial agents. Also, disk diffusion, broth microDilution, and Agar Dilution tests were compared with each other. All test method comparisons gave greater than 94% agreement for the category of susceptibility. The E Test category agreement with disk diffusion and broth microDilution was 95.1%, and with Agar Dilution it was 95.2%. The E Test results were as reliable as the results obtained by the standard antimicrobial susceptibility testing methods. Images
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comparison of the e test to Agar Dilution broth microDilution and Agar diffusion susceptibility testing techniques by using a special challenge set of bacteria
Journal of Clinical Microbiology, 1991Co-Authors: C N Baker, Sheila A Stocker, D H Culver, Clyde ThornsberryAbstract:The E Test (AB Biodisk, Solna, Sweden) is a new method for performing antimicrobial susceptibility tests. It consists of an impervious carrier (5- by 50-mm strip) with a predefined antimicrobic gradient which is placed on an inoculated Agar plate and processed like a disk diffusion test. Results are generated directly as MICs from a continuous concentration gradient covering 15 twofold Dilutions, and MICs are read where the edge of the inhibition zone intersects the strip. We compared the E Test with disk diffusion, broth microDilution, and Agar Dilution tests by using a challenge set of 195 gram-positive and gram-negative bacteria for 14 antimicrobial agents. Also, disk diffusion, broth microDilution, and Agar Dilution tests were compared with each other. All test method comparisons gave greater than 94% agreement for the category of susceptibility. The E Test category agreement with disk diffusion and broth microDilution was 95.1%, and with Agar Dilution it was 95.2%. The E Test results were as reliable as the results obtained by the standard antimicrobial susceptibility testing methods.