scholarly journals Minimum Inhibitory Concentration Breakpoints and Disk Diffusion Inhibitory Zone Interpretive Criteria for Tilmicosin Susceptibility Testing against Pasteurella Spp. Associated with Bovine Respiratory Disease

1996 ◽  
Vol 8 (3) ◽  
pp. 337-344 ◽  
Author(s):  
Thomas R. Shryock ◽  
Donald W. White ◽  
J. Mitchell Staples ◽  
Carolyn S. Werner
Keyword(s):  
Respiratory Disease ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Bovine Respiratory Disease ◽  
Disk Diffusion ◽  
National Committee ◽  
Pharmacokinetic Data ◽  
In Vitro Test ◽  
Disk Diffusion Testing

Tilmicosin is a novel macrolide antibiotic developed for exclusive use in veterinary medicine. The first tilmicosin-containing product was approved to treat bovine respiratory disease associated with pasteurellae. The development of antimicrobial susceptibility testing guidelines for tilmicosin was predicated on the relationship of clinical efficacy studies that demonstrated a favorable therapeutic outcome, on pharmacokinetic data, and on in vitro test data, as recommended by the National Committee for Clinical Laboratory Standards (NCCLS). The NCCLS-approved breakpoints for the MIC dilution testing are resistant ‡ 32 g/ml, intermediate 16 g/ml, and susceptible £ 8 g/ml. The zone of inhibition interpretive criteria for disk diffusion testing with a 15- g disk are resistant £ 10 mm, intermediate 11–13 mm, and susceptible ‡ 14 mm.

Comparison of the Vitek GPS-TB Card With Disk Diffusion Testing for Predicting the Susceptibility of Enterococci to Vancomycin

1999 ◽  
Vol 123 (7) ◽  
pp. 622-625
Author(s):  
Natalie Williams-Bouyer ◽  
Barbara S. Reisner ◽  
Carla E. Woodmansee ◽  
Pamela S. Falk ◽  
C. Glen Mayhall
Keyword(s):  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Test Methods ◽  
Disk Diffusion ◽  
National Committee ◽  
Repeat Testing ◽  
Disk Diffusion Testing ◽  
Intermediate Results

Abstract Objective.—To compare the ability of the Vitek GPS-TB card with disk diffusion testing for determining the susceptibility of enterococci to vancomycin. Design.—Vitek susceptibility testing was performed using the GPS-TB card and software version R05.03. Disk diffusion susceptibility testing was performed according to National Committee for Clinical Laboratory Standards guidelines. When discrepancies occurred between the interpretation of Vitek and disk diffusion, both tests were repeated and the epsilometer test (E test) and agar screen containing 6 μg/mL vancomycin were performed. Results.—Of 415 isolates tested, 313 were susceptible to vancomycin and 97 were resistant to vancomycin by both test methods. Two isolates were intermediate by Vitek and resistant by disk diffusion, 2 were intermediate by Vitek and susceptible by disk diffusion, and 1 was susceptible by Vitek and intermediate by disk diffusion. All but 1 of these latter 5 isolates (intermediate by Vitek and susceptible by disk diffusion) were available for retesting. On repeat testing, the 2 isolates that were intermediate by Vitek and resistant by disk diffusion were resistant by both methods, the 1 isolate that was intermediate by Vitek and susceptible by disk diffusion was susceptible by both methods, and the isolate that was susceptible by Vitek and intermediate by disk diffusion was also susceptible by both methods. These results were confirmed by E test and agar screen. Conclusion.—We found the results of the GPS-TB card compared well with disk diffusion. However, isolates with intermediate results by Vitek should be retested using another method, such as the E test.

scholarly journals Minimum Inhibitory Concentration Breakpoints and Disk Diffusion Inhibitory Zone Interpretive Criteria for Tilmicosin Susceptibility Testing against Pasteurella Multocida and Actinobacillus Pleuropneumoniae Associated with Porcine Respiratory Disease

2002 ◽  
Vol 14 (5) ◽  
pp. 389-395 ◽  
Author(s):  
Thomas R. Shryock ◽  
J. Mitchell Staples ◽  
David C. DeRosa
Keyword(s):  
Minimum Inhibitory Concentration ◽  
Respiratory Disease ◽  
Pasteurella Multocida ◽  
Susceptibility Testing ◽  
Inhibitory Concentration ◽  
Actinobacillus Pleuropneumoniae ◽  
Disk Diffusion ◽  
Pharmacokinetic Data ◽  
In Vitro Test ◽  
Porcine Respiratory

Tilmicosin is a novel macrolide antibiotic developed for exclusive use in veterinary medicine. Tilmicosin has been approved as a feed premix to control porcine respiratory disease associated with Pasteurella multocida and Actinobacillus pleuropneumoniae. The development of antimicrobial susceptibility testing guidelines for tilmicosin was predicated on the relationship of clinical efficacy studies that demonstrated a favorable therapeutic outcome, on pharmacokinetic data, and on in vitro test data, as recommended by the National Committee for Clinical Laboratory Standards (NCCLS). The approved breakpoints for the minimum inhibitory concentration dilution testing for both species are resistant, ≥32 μg/ml, and susceptible, ≤16 μg/ml. The zone of inhibition interpretive criteria for disk diffusion testing with a 15-μg tilmicosin disk are resistant, ≤10 mm, and susceptible, ≥11mm.

scholarly journals Recommendation of an Appropriate Medium for In Vitro Drug Susceptibility Testing of the Fish Pathogen Tenacibaculum maritimum

2005 ◽  
Vol 49 (1) ◽  
pp. 82-87 ◽  
Author(s):  
Ruben Avendaño-Herrera ◽  
Rute Irgang ◽  
Soledad Núñez ◽  
Jesús L. Romalde ◽  
Alicia E. Toranzo
Keyword(s):  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Drug Susceptibility Testing ◽  
The Other ◽  
Disk Diffusion ◽  
National Committee ◽  
Good Growth ◽  
Good Correspondence ◽  
In Vitro Susceptibility

ABSTRACT In the present study, Anacker and Ordal agar, marine agar (MA), and Flexibacter maritimus medium (FMM) were compared with the dilute versions of Mueller-Hinton agar (DMHA) medium recommended by the National Committee for Clinical Laboratory Standards (NCCLS) for their use in disk diffusion tests with Tenacibaculum maritimum strains and to calculate the MICs of five drugs by the Etest method. Preliminary growth tests performed with 32 strains of this pathogen on each medium revealed that all strains failed to grow on DMHA, while the remaining media supported good growth of all isolates. In the susceptibility tests, which were carried out with the other three media, all strains were resistant to oxolinic acid and were highly susceptible to amoxicillin and trimethoprim-sulfamethoxazole, showing a good correspondence with the Etest values, which ranged from 0.064 to 0.75 and 0.006 to 1.5 μg/ml, respectively. Enrofloxacin and oxytetracycline produced significantly smaller inhibition zones and MICs on MA than on the other media assayed. However, fast, clear, and well-defined zones of inhibition were displayed for all strains at 24 h of incubation only on FMM by both the disk diffusion assay and Etest. In addition, FMM prepared with commercial sea salts instead of seawater was also suitable for bacterial isolation as well as for susceptibility testing. On the basis of these results, the use of FMM to determine the in vitro susceptibility of T. maritimum and its inclusion in a future revision of the NCCLS M42 report are recommended.

Use of spectrophotometric reading for in vitro antifungal susceptibility testing ofAspergillusspp.

1999 ◽  
Vol 45 (10) ◽  
pp. 871-874 ◽  
Author(s):  
Eric Dannaoui ◽  
Florence Persat ◽  
Marie-France Monier ◽  
Elisabeth Borel ◽  
Marie-Antoinette Piens ◽  
...  
Keyword(s):  
Amphotericin B ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Antifungal Susceptibility ◽  
Reference Method ◽  
Antifungal Susceptibility Testing ◽  
Aspergillus Species ◽  
National Committee ◽  
Broth Microdilution Method

A comparative study of visual and spectrophotometric MIC endpoint determinations for antifungal susceptibility testing of Aspergillus species was performed. A broth microdilution method adapted from the National Committee for Clinical Laboratory Standards (NCCLS) was used for susceptibility testing of 180 clinical isolates of Aspergillus species against amphotericin B and itraconazole. MICs were determined visually and spectrophotometrically at 490 nm after 24, 48, and 72h of incubation, and MIC pairs were compared. The agreement between the two methods was 99% for amphotericin B and ranged from 95 to 98% for itraconazole. It is concluded that spectrophotometric MIC endpoint determination is a valuable alternative to the visual reference method for susceptibility testing of Aspergillus species.Key words: antifungal, susceptibility testing, Aspergillus, spectrophotometric reading.

Assessment of Laboratory Performance With Streptococcus pneumoniae Antimicrobial Susceptibility Testing in the United States

1999 ◽  
Vol 123 (4) ◽  
pp. 285-289 ◽  
Author(s):  
Gary V. Doern ◽  
Angela B. Brueggemann ◽  
Michael A. Pfaller ◽  
Ronald N. Jones
Keyword(s):  
United States ◽  
Streptococcus Pneumoniae ◽  
Antimicrobial Agents ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
The United States ◽  
National Committee ◽  
In Vitro Susceptibility ◽  
Susceptibility Tests

Abstract Objective.—To assess the performance of clinical microbiology laboratories in the United States when conducting in vitro susceptibility tests with Streptococcus pneumoniae. Methods.—The results of a nationwide College of American Pathologists Proficiency Survey test sample, in which susceptibility testing of an isolate of S pneumoniae was performed, were assessed with respect to precision and accuracy. Results.—Wide variability was noted among participating laboratories with both minimum inhibitory concentration procedures and disk diffusion susceptibility tests when both methods were applied to S pneumoniae. Despite this high degree of variation, categorical interpretive errors were uncommon. Numerous laboratories reported results for antimicrobial agents that are not recommended by the National Committee for Clinical Laboratory Standards for tests with S pneumoniae. Conclusions.—Current susceptibility testing practices with S pneumoniae in the United States indicate limited precision and a tendency for laboratories to test and report results obtained with antimicrobial agents of questionable therapeutic value against this organism. Continued efforts to standardize susceptibility testing of S pneumoniae in the United States are warranted. In addition, modifications of existing interpretive criteria may be necessary.

scholarly journals Interpretive Breakpoints for Fluconazole and Candida Revisited: a Blueprint for the Future of Antifungal Susceptibility Testing

2006 ◽  
Vol 19 (2) ◽  
pp. 435-447 ◽  
Author(s):  
M. A. Pfaller ◽  
D. J. Diekema ◽  
D. J. Sheehan
Keyword(s):  
Clinical Studies ◽  
Randomized Clinical Trials ◽  
Clinical Laboratory ◽  
Antifungal Susceptibility ◽  
Strong Relationship ◽  
National Committee ◽  
Disk Diffusion Testing ◽  
Invasive Infections

SUMMARY Developing interpretive breakpoints for any given organism-drug combination requires integration of the MIC distribution, pharmacokinetic and pharmacodynamic parameters, and the relationship between in vitro activity and outcome from both in vivo and clinical studies. Previously, the Subcommittee for Antifungal Testing of the Clinical and Laboratory Standards Institute (CLSI [formerly National Committee for Clinical Laboratory Standards]) proposed MIC interpretive breakpoints for fluconazole and Candida spp. These breakpoints were considered to be somewhat weak, because the clinical data supporting them came largely from mucosal infections and there were very few infections involving strains with elevated fluconazole MICs. We readdress the issue of fluconazole breakpoints for Candida by using published clinical and microbiologic data to provide further validation of the breakpoints proposed by the CLSI in 1997. We also address interpretive breakpoints for agar disk diffusion testing of fluconazole. The MIC distribution for fluconazole was determined with a collection of 13,338 clinical isolates. The overall MIC at which 90% of the isolates were inhibited was 8 μg/ml: 91% were susceptible (S) at a MIC of ≤8 μg/ml and 3% were resistant (R) (MIC ≥ 64 μg/ml). Similar results were obtained for 2,190 isolates from randomized clinical trials. Analysis of available data for 1,295 patient-episode-isolate events (692 represented mucosal infections and 603 represented invasive infections) from 12 published clinical studies demonstrated an overall success rate of 77%, including 85% for those episodes in which the fluconazole MIC was ≤8 μg/ml, 67% for those episodes in which the MIC was 16 to 32 μg/ml, and 42% for those episodes with resistant (MIC ≥ 64 μg/ml) isolates. Pharmacodynamic analysis demonstrated a strong relationship between MIC, fluconazole dose, and outcome. A dose/MIC ratio of ∼25 was supportive of the following susceptibility breakpoints for fluconazole and Candida spp.: S, MIC ≤ 8 μg/ml; susceptible-dose dependent (SDD), MIC = 16 to 32 μg/ml; R, MIC ≥ 64 μg/ml. The corresponding disk test breakpoints are as follows: S, ≥19 mm; SDD, 15 to 18 mm; R, ≤14 mm.

scholarly journals Evaluation of Amphotericin B Interpretive Breakpoints for Candida Bloodstream Isolates by Correlation with Therapeutic Outcome

2006 ◽  
Vol 50 (4) ◽  
pp. 1287-1292 ◽  
Author(s):  
Benjamin J. Park ◽  
Beth A. Arthington-Skaggs ◽  
Rana A. Hajjeh ◽  
Naureen Iqbal ◽  
Meral A. Ciblak ◽  
...  
Keyword(s):  
Amphotericin B ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
National Committee ◽  
Restricted Range ◽  
Broth Microdilution ◽  
Therapeutic Success ◽  
In Vitro Susceptibility ◽  
In Vitro Susceptibility Testing

ABSTRACT One hundred seven Candida bloodstream isolates (51 C. albicans, 24 C. glabrata, 13 C. parapsilosis, 13 C. tropicalis, 2 C. dubliniensis, 2 C. krusei, and 2 C. lusitaniae strains) from patients treated with amphotericin B alone underwent in vitro susceptibility testing against amphotericin B using five different methods. Fifty-four isolates were from patients who failed treatment, defined as death 7 to 14 days after the incident candidemia episode, having persistent fever of ≥5 days' duration after the date of the incident candidemia, or the recurrence of fever after two consecutive afebrile days while on antifungal treatment. MICs were determined by using the Clinical Laboratory Standards Institute (formally National Committee for Clinical Laboratory Standards) broth microdilution procedure with two media and by using Etest. Minimum fungicidal concentrations (MFCs) were also measured in two media. Broth microdilution tests with RPMI 1640 medium generated a restricted range of MICs (0.125 to 1 μg/ml); the corresponding MFC values ranged from 0.5 to 4 μg/ml. Broth microdilution tests with antibiotic medium 3 produced a broader distribution of MIC and MFC results (0.015 to 0.25 μg/ml and 0.06 to 2 μg/ml, respectively). Etest produced the widest distribution of MICs (0.094 to 2 μg/ml). However, none of the test formats studied generated results that significantly correlated with therapeutic success or failure.

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 Use of the National Committee for Clinical Laboratory Standards Guidelines for Disk Diffusion Susceptibility Testing in New York State Laboratories

2000 ◽  
Vol 38 (9) ◽  
pp. 3341-3348 ◽  
Author(s):  
Julia A. Kiehlbauch ◽  
George E. Hannett ◽  
Max Salfinger ◽  
Wendy Archinal ◽  
Catherine Monserrat ◽  
...  
Keyword(s):  
New York ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Bacterial Species ◽  
New York State ◽  
Disk Diffusion ◽  
National Committee ◽  
York State ◽  
Excess Number ◽  
Inoculum Preparation

Accurate antimicrobial susceptibility testing is vital for patient care and surveillance of emerging antimicrobial resistance. The National Committee for Clinical Laboratory Standards (NCCLS) outlines generally agreed upon guidelines for reliable and reproducible results. In January 1997 we surveyed 320 laboratories participating in the New York State Clinical Evaluation Program for General Bacteriology proficiency testing. Our survey addressed compliance with NCCLS susceptibility testing guidelines for bacterial species designated a problem (Staphylococcus aureus and Enterococcusspecies) or fastidious (Streptococcus pneumoniae,Haemophilus influenzae, and Neisseria gonorrhoeae) organism. Specifically, we assessed compliance with guidelines for inoculum preparation, medium choice, number of disks per plate, and incubation conditions for disk diffusion tests. We also included length of incubation for S. aureus andEnterococcus species. We found overall compliance with the five characteristics listed above in 80 of 153 responding laboratories (50.6%) for S. aureus and 72 of 151 (47.7%) laboratories for Enterococcus species. The most common problem was an incubation time shortened to less than 24 h. Overall compliance with the first four characteristics was reported by 92 of 221 (41.6%) laboratories for S. pneumoniae, 49 of 163 (30.1%) laboratories for H. influenzae, and 11 of 77 (14.3%) laboratories for N. gonorrhoeae. Laboratories varied from NCCLS guidelines by placing an excess number of disks per plate. Laboratories also reported using alternative media forEnterococcus species, N. gonorrhoeae, andH. influenzae. This study demonstrates a need for education among clinical laboratories to increase compliance with NCCLS guidelines.

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