Ofloxacin susceptibility testing quality control parameters for microdilution and disk diffusion, and confirmation of disk diffusion interpretive criteria.

The susceptibilities of 221 clinical isolates to ofloxacin were tested simultaneously by broth microdilution and disk diffusion methods with commercially prepared 5-micrograms ofloxacin disks. The acceptability of the following previously proposed zone diameter breakpoints was confirmed: greater than or equal to 16 mm, susceptible; 13 to 15 mm, intermediate; less than or equal to 12 mm, resistant. On the basis of a multilaboratory collaborative study, the following are proposed as acceptable ofloxacin MIC ranges for quality control organisms: Escherichia coli ATCC 25922, 0.03 to 0.06 micrograms/ml; Staphylococcus aureus ATCC 29213, 0.12 to 0.5 micrograms/ml; Pseudomonas aeruginosa ATCC 27853 and Enterococcus faecalis ATCC 29212, 1.0 to 4.0 micrograms/ml. Ofloxacin quality control zone diameter ranges for the disk diffusion test are tentatively proposed, but variations in the performance of different lots of Mueller-Hinton agar may prove to be a serious problem for users.     

Tentative disk diffusion susceptibility interpretive criteria for pefloxacin.

Standardized broth microdilution and disk diffusion susceptibility tests for pefloxacin were performed on 585 clinical isolates. The 5-micrograms pefloxacin disk is recommended, and the following breakpoints are proposed: susceptible, greater than or equal to 19 mm (MIC, less than or equal to 2.0 micrograms/ml); resistant, less than or equal to 15 mm (MIC, greater than 4.0 micrograms/ml); and intermediate, 16 to 18 mm.     

Disk diffusion susceptibility tests with norfloxacin: confirmation of proposed interpretive criteria

One hundred and eighty three clinical isolates of aerobic bacteria were tested against norfloxacin by both agar dilution (WHO-ICS) and disk diffusion test procedures (standardized FDA single disk test). Two experimental 10μg norfloxacin disks were studied. Results were analyzed in terms of recently recommended breakpoints for clinical susceptibility (MIC ? 16μg/ml, zone diameter ? 17 mm) and resistance (MIC ? 32μg/ml, zone diameter ? 12 mm). Excellent correlation was demonstrated by statistical analysis between paired MIC and zone size values (average value for each MIC; r=?0.9782). An MIC of 16μg/ml was found to correlate with a zone of 10.4 mm. Application of the recommended zone size breakpoints resulted in prediction of 177 isolates as being susceptible while six (3.3 %) were predicted to be either intermediate or resistant. The findings of this study validate the earlier recommendations stated above.     

Proposed quality control and interpretive criteria for disk diffusion susceptibility testing with enoxacin.

The standardized disk diffusion test, in which a 10-micrograms enoxacin disk is used, was performed and microbroth dilution MICs were determined to establish individual test control values with Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, and S. aureus ATCC 29213. In addition, regression analysis correlating inhibitory zone diameter with MICs for approximately 400 gram-negative clinical isolates was performed. Based on linear regression and error rate-bounded analyses, criteria for the category calls of isolates are proposed.     

Levofloxacin disk potency and tentative interpretive criteria for susceptibility tests.

Levofloxacin disk susceptibility test criteria were evaluated by testing 350 bacterial isolates. Either 5- or 10-micrograms disks could be used satisfactorily. A 5-micrograms levofloxacin disk with zone size breakpoints of < or = 12 mm for resistance (MIC, > or = 8.0 micrograms/ml) and > or = 16 mm for susceptibility (MIC, < or = 2.0 micrograms/ml) is recommended.     

Temafloxacin disk potency and tentative interpretive criteria for susceptibility tests.

Temafloxacin disk susceptibility test criteria were evaluated by testing 697 bacterial isolates. Either 5- or 10-micrograms disks could be used satisfactorily. A 5-micrograms temafloxacin disk with zone size breakpoints of less than or equal to 12 mm for resistance (MIC, greater than 4.0 micrograms/ml) and greater than 16 mm for susceptibility (MIC, less than or equal to 2.0 micrograms/ml) is recommended.     

Tentative interpretive criteria for disk diffusion susceptibility testing of sparfloxacin.

Susceptibility to sparfloxacin was tested simultaneously by the agar dilution and disk diffusion methods. For tests with 5-micrograms sparfloxacin disks, we propose that the breakpoints for the susceptibility and resistance categories should be > or = 19 and < or = 15 mm, respectively. Most minor discrepancies involved tests with pseudomonads.     

Cefoperazone disk diffusion susceptibility test: confirmation of the tentative interpretive criteria, Pseudomonas aeruginosa cross-resistance, and determination of quality control performance limits.

Cefoperazone disk diffusion test and minimum inhibitory concentration comparison studies were performed on 421 recent bacterial isolates, using 30- and 75-micrograms commercially prepared disks. Acceptable correlation coefficients (-0.82 to -0.86) and very major (false-susceptible) interpretive error rates (less than 1%) were obtained with both disk concentrations. The interpretive criteria for both disks were identical. Using the preferred 75-micrograms disk, the Thornsberry et al. criteria (J. Clin. Microbiol. 15:769-776, 1982) of greater than or equal to 18 mm = susceptible (less than or equal to 32 micrograms/ml) and less than or equal to 14 mm = resistant (greater than 64 micrograms/ml) resulted in only 5.5% of strains having indeterminate-range zone diameters; the 30-micrograms disk had 6.9% of strains with indeterminate zone diameters. The 75-micrograms disk, excluding the testing of enterococci, minimized the very major and other interpretive errors to less than 5%. Larger zone diameters will contribute few technical problems with either disk concentration. Data from 1,320 zone diameters submitted for each quality control strain indicated no significant (P greater than 0.05) difference between disks made by the three major manufacturers, and consistent results were obtained within each laboratory with numerous lots of Mueller-Hinton agar (except for one manufacturer). Individual daily test and accuracy quality control ranges were calculated from clinical investigator laboratory data at 16 hospitals based on mean zone sizes and from an additional 8 laboratories with both mean and median calculations. The quality control data were nearly identical, and ranges calculated by the two methods were very similar. Susceptibility tests of Pseudomonas aeruginosa indicate that the cefoperazone disk or minimum inhibitory concentration test would accurately predict P. aeruginosa susceptibility test results for other pseudomonas-active cephalosporins (cefsulodin and ceftazidime), thus producing no very major interpretive errors.     

Interpretive criteria and tentative quality control limits for apalcillin disk susceptibility tests.

In vitro studies with 661 bacterial isolates were performed to establish interpretive criteria. In addition, a nine-laboratory study was performed to establish quality control limits for tests with 100-micrograms apalcillin disks and to confirm testing criteria for tests with 100-micrograms piperacillin disks. The two drugs were very similar, and nearly identical criteria were recommended for interpretation and for control of the two types of disks. Neither disk is recommended for testing Staphylococcus spp. or Haemophilus spp.; with other microorganisms, zone size limits of less than or equal to 13 mm (resistant) and greater than or equal to 18 mm (susceptible) are proposed for tests with 100-micrograms apalcillin disks.     

Development of interpretive criteria and quality control limits for broth microdilution and disk diffusion antimicrobial susceptibility testing of Streptococcus pneumoniae.

A five-center collaborative study was undertaken to develop quality control and specific interpretive criteria for susceptibility testing of Streptococcus pneumoniae against 12 antimicrobial agents. MICs were determined for 248 pneumococcal clinical isolates (with an emphasis on resistant strains) by use of the National Committee for Clinical Laboratory Standards (NCCLS)-recommended broth microdilution procedure incorporating lysed horse blood-supplemented Mueller-Hinton broth. NCCLS disk diffusion testing was also performed for each isolate by using Mueller-Hinton sheep blood agar incubated in 5% CO2. Repetitive testing of S. pneumoniae ATCC 49619 with different sources and lots of media and disks allowed development of quality control ranges which encompassed approximately 95% of MIC and zone size values observed in the study. Good intra- and interlaboratory reproducibilities were seen with these testing methods and all of the drugs examined. On the basis of the results of this study, MIC interpretive criteria are proposed for 11 agents. Comparisons of MICs and disk diffusion zone sizes allowed disk diffusion zone size interpretive criteria to be proposed for five drugs and confirmed the use of the oxacillin disk test for prediction of penicillin susceptibility among pneumococci. Excessive numbers of minor-category interpretive errors precludes recommendation at this time of the disk diffusion method for testing of pneumococci against five of the drugs. Use of these proposed quality control and interpretive criteria should provide for reproducible test results and allow recognition of recently emerging resistance among pneumococcal clinical isolates.     

Tentative disk diffusion susceptibility interpretive criteria for BMY-28142, a new cephalosporin.

A total of 750 bacterial isolates, including 37 different species, were tested for susceptibility to BMY-28142 by standardized broth microdilution and disk diffusion tests. The zone diameter interpretive criteria tentatively suggested for the 30-micrograms BMY-28142 disk are as follows: susceptible = greater than or equal to 18 mm (MIC less than or equal to 8.0 micrograms/ml), resistant = less than or equal to 14 mm (MIC greater than or equal to 32 micrograms/ml), and indeterminate = 15 to 17 mm.     

Interpretive criteria and quality control limits for ceftibuten disk susceptibility tests. Collaborative Antimicrobial Susceptibility Testing Group.

In vitro studies were undertaken to evaluate susceptibility tests with 30-micrograms ceftibuten disks. The following interpretive criteria were proposed: less than or equal to 17 mm for resistance (MIC, greater than or equal to 32 micrograms/ml) and greater than or equal to 21 mm for susceptibility (MIC, less than or equal to 8.0 micrograms/ml). A multilaboratory quality control study led to the conclusion that Escherichia coli ATCC 25922 should provide zones 29 to 35 mm in diameter.     

Evaluation of teicoplanin and vancomycin disk susceptibility tests.

Disk tests with two glycopeptide antibiotics, teicoplanin and vancomycin, were evaluated, and MICs were compared with those of fusidic acid and coumermycin. For tests with 30-micrograms vancomycin disks, we recommend modification of the current zone size standards to less than or equal to 10 mm for resistant and greater than or equal 15 mm for susceptible. For teicoplanin disk tests, 30-micrograms disks are recommended, with zone size interpretive standards of less than or equal to 10 and greater than or equal 14 mm. Since no resistant clinical isolates are available at this time, susceptibility testing of either drug is rarely necessary, and zone size standards are tentative.     

Susceptibility testing of carumonam: interpretive criteria for 30-microgram disk tests and quality control guidelines for disk diffusion and broth microdilution methods.

Carumonam 30-microgram disk diffusion tests with 342 gram-negative organisms suggested modifying earlier interpretive zone criteria, i.e., a susceptibility zone diameter of greater than or equal to 23 mm (less than or equal to 8.0 micrograms/ml MIC correlate) and a resistance zone diameter of less than or equal to 17 mm (greater than or equal to 32 micrograms/ml MIC correlate). Quality assurance guidelines were determined by multilaboratory investigations. Recommended limits were calculated for the gram-negative quality control organisms only. For Escherichia coli ATCC 25922, the recommended limits are 30 to 36 mm and 0.03 to 0.25 micrograms/ml, and for Pseudomonas aeruginosa ATCC 27853, they are 24 to 32 mm and 1.0 to 4.0 micrograms/ml.     

Quality control parameters and interpretive criteria for in vitro susceptibility tests with the macrolide azithromycin

Quality control parameters for broth microdilution and disk diffusion susceptibility tests were defined and the interpretive criteria for disk diffusion tests reviewed. For interpretation of tests with 15 µg azithromycin disks, the following criteria are recommended: 19 mm for the susceptible category (MIC2.0 µg/ml) and 15 mm for the resistant category (MIC8.0 µg/ml). Using these criteria, there was 97 % overall agreement between broth dilution and disk diffusion tests;Haemophilus influenzae isolates were susceptible to azithromycin by both methods. The quality control strainStaphylococcus aureus ATCC 25923 gave zones of 21 to 26 mm in diameter in a six-laboratory collaborative study. In azithromycin broth microdilution tests the following MIC control limits are recommended:Escherichia coli ATCC 25922, 2.0–8.0 µg/ml;Staphylococcus aureus ATCC 29213, 0.25–1.0 µg/ml; andEnterococcus faecalis ATCC 29212, 1.0–4.0 µg/ml.Collaborating investigators contributing data to the quality control studies include P. C. Fuchs, St. Vincent Hospital and Medical Center, Portland, Oregon; S. D. Allen, Indiana University Medical Center, Indianapolis, Indiana; E. H. Gerlach, St. Francis Regional Medical Center, Wichita, Kansas; J. A. Washington, The Cleveland Clinic Foundation, Cleveland, Ohio; L. B. Reller, University of Colorado Medical Center, Denver, Colorado, USA.     

Proposed disk diffusion susceptibility criteria for ofloxacin.

Disk diffusion zone diameter breakpoint criteria for ofloxacin were tentatively established by correlating MICs with 1-, 3-, and 5-micrograms disk inhibitory zone diameters for 638 bacterial isolates representing 36 species. We recommend use of 5-micrograms disks with the following breakpoints: susceptible (MIC, less than or equal to 2.0 micrograms/ml), greater than or equal to 16 mm; intermediate (MIC, 4.0 micrograms/ml), 13 to 15 mm; and resistant (MIC, greater than or equal to 8.0 micrograms/ml), less than or equal to 12 mm.     

Quality control limits for ampicillin, carbenicillin, mezlocillin, and piperacillin disk diffusion susceptibility tests: a collaborative study

A multilaboratory in vitro study was carried out to determine disk diffusion susceptibility testing quality control limits for two new semisynthetic penicillins, mezlocillin and piperacillin. Existing limits for carbenicillin and ampicillin were reevaluated. Multiple tests (which followed standards set by the National Committee for Clinical Laboratory Standards ASM-2 revised) were performed in nine laboratories by different technologists using disks and Mueller-Hinton agar from different manufacturers. Clinically significant differences between disks produced by different manufacturers were not noted. Inhibitory zone diameter measurements from all laboratories were analyzed, and upper and lower control limits were established by using the overall median +/-0.5 the median range of the individual laboratory measurements as determining parameters. Close agreement of the data in this study with the results of national proficiency testing and quality control programs for ampicillin and carbenicillin supports the validity of our approach to making initial recommendations for quality control guidelines for new antimicrobial agents.     

Quality control limits for microdilution susceptibility tests with norfloxacin.

A multilaboratory study was designed to define quality control limits for microdilution susceptibility tests with norfloxacin. The following limits were proposed: for Escherichia coli ATCC 25922, 0.03 to 0.125 micrograms/ml; for Pseudomonas aeruginosa ATCC 27853, 1.0 to 4.0 micrograms/ml; for Staphylococcus aureus ATCC 29213, 0.5 to 2.0 micrograms/ml; and for Streptococcus faecalis ATCC 29212, 2.0 to 8.0 micrograms/ml. The latter represents a change in the previously recommended control limits.     

Standardization of disk diffusion and agar dilution susceptibility tests for Neisseria gonorrhoeae: interpretive criteria and quality control guidelines for ceftriaxone, penicillin, spectinomycin, and tetracycline.

A six-laboratory study developed a standardized method for determining the susceptibilities of Neisseria gonorrhoeae strains to penicillin, tetracycline, spectinomycin, and ceftriaxone. Three quality control organisms were also selected, and quality assurance guidelines were initially generated for the disk diffusion and agar dilution methods. The medium recommended for gonococcal susceptibility testing was GC agar with a defined "XV-like" supplement. The supplement should be free of cysteine, a component implicated in the inactivation of some newer beta-lactam compounds. Penicillin, tetracycline, spectinomycin, and ceftriaxone were stable in agar plates stored at 3 to 5 degrees C for at least 2 weeks. Numerous GC agar and drug disk lots were used during the trials without significant variation in test results. Several other gonococcal strains were recommended for additional medium quality assurance. The disk quality control zone limits were established for N. gonorrhoeae ATCC 49226 (formerly CDC F-18) and Staphylococcus aureus ATCC 25923. MIC quality control ranges were also developed for N. gonorrhoeae ATCC 49226 and S. aureus ATCC 29213. The interpretive criteria for penicillin were as follows: susceptibility, greater than or equal to 47 mm (diameter of inhibition zone) (less than or equal to 0.06 micrograms/ml [MIC]); resistance, less than or equal to 26 mm (greater than or equal to 2 micrograms/ml). For tetracycline they were as follows: susceptibility, greater than or equal to 38 mm (less than or equal to 0.25 microgram/ml); resistance, less than or equal to 30 mm (greater than or equal to 2 micrograms/ml). For spectinomycin they were as follows: susceptibility, >/= 18 mm (/= 128 micrograms/ml). For ceftriaxone susceptibility, the criterion was >/= 35 mm (相似文献