Contents Page Standing Committee members 4 Changes in document 5 Preface 6 Disc Diffusion Method for Antimicrobial Susceptibility Testing 1. Preparation of plates 8 2. Selection of control organisms 9 2 a Control strains to monitor test performance of antimicrobial susceptibility 10 testing 2b Control strains used to confirm that the method will detect resistance 10 3. Preparation of inoculum 10 4. Inoculation of agar plates 14 5. Antimicrobial discs 14 6. Incubation 15 7. Measuring and interpretation of susceptibility 17 8. Oxacillin/cefoxitin testing of staphylococci 18 Acknowledgment 21 References 21 Control of disc diffusion antimicrobial susceptibility testing 22 1 Control strains 22 2 Maintenance of control strains 22 3 Calculation of control ranges for disc diffusion 22 4 Frequency of routine testing with control strains 22 5 Use of control data to monitor the performance of disc diffusion tests 22 6 Recognition of atypical results for clinical isolates 23 7 Investigation of possible sources of error 23 8 Reporting susceptibility results when controls indicate problems 24 Acceptable ranges for control strains for: 2 Iso-Sensitest agar incubated at 35-370C in air for 18-20h 25 3 Iso-Sensitest agar supplemented with 5% defibrinated horse blood, 28 with or without the addition of NAD, incubated at 35-370C in air for 4 Detection of methicillin/oxacillin/cefoxitin resistance in staphylococci 28 5 Iso-Sensitest agar supplemented with 5% defibrinated blood, with 29 or without the addition of NAD, incubated at 35-370C in 10% CO2/10% H2 /80% N2 for 18-20 h
Contents Page Standing Committee members 4 Changes in document 5 Preface 6 Disc Diffusion Method for Antimicrobial Susceptibility Testing 1. Preparation of plates 8 2. Selection of control organisms 9 2 a Control strains to monitor test performance of antimicrobial susceptibility testing 10 2b Control strains used to confirm that the method will detect resistance 10 3. Preparation of inoculum 10 4. Inoculation of agar plates 14 5. Antimicrobial discs 14 6. Incubation 15 7. Measuring and interpretation of susceptibility 17 8. Oxacillin/cefoxitin testing of staphylococci 18 Acknowledgment 21 References 21 Control of disc diffusion antimicrobial susceptibility testing 22 1 Control strains 22 2 Maintenance of control strains 22 3 Calculation of control ranges for disc diffusion 22 4 Frequency of routine testing with control strains 22 5 Use of control data to monitor the performance of disc diffusion tests 22 6 Recognition of atypical results for clinical isolates 23 7 Investigation of possible sources of error 23 8 Reporting susceptibility results when controls indicate problems 24 Acceptable ranges for control strains for: 2 Iso-Sensitest agar incubated at 35-370C in air for 18-20h 25 3 Iso-Sensitest agar supplemented with 5% defibrinated horse blood, with or without the addition of NAD, incubated at 35-370C in air for 28 4 Detection of methicillin/oxacillin/cefoxitin resistance in staphylococci 28 5 Iso-Sensitest agar supplemented with 5% defibrinated blood, with or without the addition of NAD, incubated at 35-370C in 10% CO2/10% H2 /80% N2 for 18-20 h 29