| How is a standardized inoculum prepared for testing? | using the direct colony suspension method | National Centre for Disease Control, India Note: Add the antibiotic stock while the autoclaved media temperature is 45 -50oC. Immediately after adding antibiotic stock solution, slowly mix it and pour approx. 5 plates. Inoculum preparation Make fresh subcultures from glycerol stocks/slants/ agar plates on Tryptic Soya Agar (TSA) or any other non-selective media on a day before putting up the VAS test and incubate at 35-37oC in a BOD incubator for 18 to 24 h. Put up the ATCC QC strains with each VAS plate; refer to QC Section, page 76. Use a fresh culture of the strain to be tested and prepare a suspension of the tested strain equivalent to 0. McFarland standard. Prepare a standardized inoculum of 0. McFarland using the direct colony suspension method. | 731 | definition | 1.000 | https://ncdc.mohfw.gov.in/uploads/pdf/amr9.pdf | McFarland using the direct colony suspension method. | 76 | page=76,block=1 | 0.700 | valid |
| How is the MIC determined in colistin agar plate testing? | as the lowest colistin agar plate concentration that completely inhibits the growth of the test isolate | Colony counts of inoculum suspensions Refer to Chapter 2, Page 44 Results and Interpretation Examine the purity plate to ensure the inoculum is pure. Examine the growth control plate, i.e., 0 µg/ml colistin agar plate, which must demonstrate confluent growth of all the test strains and QC strains for the test to be valid. Examine the colistin plates carefully with transmitted light for the colony or light film of growth. Read the MIC as the lowest colistin agar plate concentration that completely inhibits the growth of the test isolate (e.g., even 1 colony would be considered growth). Result can be recorded as + or -, + is equivalent to growth, - is equivalent to no growth. (Figure 4.2) | 446 | definition | 1.000 | https://ncdc.mohfw.gov.in/uploads/pdf/amr9.pdf | Read the MIC as the lowest colistin agar plate concentration that completely inhibits the growth of the test isolate (e.g., even 1 colony would be considered growth). | 70 | page=70,block=5 | 0.700 | valid |
| How is the MIC of Colistin determined in broth microdilution tests? | the lowest colistin concentration that completely inhibits the organism’s growth in the microdilution wells | Determining broth microdilution end points • Read the MIC of Colistin as the lowest colistin concentration that completely inhibits the organism’s growth in the microdilution wells as detected by the unaided eye. • Compare the amount of growth in the wells containing the antibiotic with the amount of growth in the growth control well (column 11) in each set of tests when determining the growth end points. • For a test to be considered valid, acceptable growth (definite turbidity or button) must occur in the growth-control well | 73 | definition | 1.000 | https://ncdc.mohfw.gov.in/uploads/pdf/amr9.pdf | Determining broth microdilution end points • Read the MIC of Colistin as the lowest colistin concentration that completely inhibits the organism’s growth in the microdilution wells as detected by the unaided eye. | 46 | page=46,block=1 | 0.700 | valid |
| What does a '+' result indicate in colistin agar plate testing? | + is equivalent to growth | Colony counts of inoculum suspensions Refer to Chapter 2, Page 44 Results and Interpretation Examine the purity plate to ensure the inoculum is pure. Examine the growth control plate, i.e., 0 µg/ml colistin agar plate, which must demonstrate confluent growth of all the test strains and QC strains for the test to be valid. Examine the colistin plates carefully with transmitted light for the colony or light film of growth. Read the MIC as the lowest colistin agar plate concentration that completely inhibits the growth of the test isolate (e.g., even 1 colony would be considered growth). Result can be recorded as + or -, + is equivalent to growth, - is equivalent to no growth. (Figure 4.2) | 636 | definition | 1.000 | https://ncdc.mohfw.gov.in/uploads/pdf/amr9.pdf | Result can be recorded as + or -, + is equivalent to growth, - is equivalent to no growth. | 70 | page=70,block=5 | 0.700 | valid |
| What does a '-' result indicate in colistin agar plate testing? | - is equivalent to no growth | Colony counts of inoculum suspensions Refer to Chapter 2, Page 44 Results and Interpretation Examine the purity plate to ensure the inoculum is pure. Examine the growth control plate, i.e., 0 µg/ml colistin agar plate, which must demonstrate confluent growth of all the test strains and QC strains for the test to be valid. Examine the colistin plates carefully with transmitted light for the colony or light film of growth. Read the MIC as the lowest colistin agar plate concentration that completely inhibits the growth of the test isolate (e.g., even 1 colony would be considered growth). Result can be recorded as + or -, + is equivalent to growth, - is equivalent to no growth. (Figure 4.2) | 663 | definition | 1.000 | https://ncdc.mohfw.gov.in/uploads/pdf/amr9.pdf | Result can be recorded as + or -, + is equivalent to growth, - is equivalent to no growth. | 70 | page=70,block=5 | 0.700 | valid |
| What does testing on consecutive test days mean in the 15-replicate plan? | testing of QC strains each day tests are performed on isolates | The 15-Replicate (3× 5 Day) Plan • Test three replicates of each applicable QC strain using individual inoculum preparation for five consecutive test days and document results. • After completing the 15-replicate (3 × 5 day) plan, the lab can undergo weekly QC testing. • If completing the 15-replicate (3 × 5 day) plan is unsuccessful, take corrective action as appropriate, and continue daily QC testing. (Refer to Table 6.5, page no. 94) Note: Testing on “consecutive test days” means testing of QC strains each day tests are performed on isolates. It does not refer to calendar days. Implementing weekly quality control testing • Implement Weekly QC testing once satisfactory performance with daily QC testing has been documented. | 488 | definition | 1.000 | https://ncdc.mohfw.gov.in/uploads/pdf/amr9.pdf | 94) Note: Testing on “consecutive test days” means testing of QC strains each day tests are performed on isolates. | 84 | page=84,block=10 | 0.700 | valid |
| What does the acronym EUCAST mean in antimicrobial susceptibility testing? | European Committee on Antimicrobial Susceptibility Testing | National Centre for Disease Control, India Acronyms AST Antimicrobial Susceptibility testing ATCC American Type Culture Collection BaSO4 Barium Sulphate BHI Brain Heart Infusion BMD Broth Microdilution BOD Biological Oxygen Demand CaMHB Cation Adjusted Mueller Hinton Broth CFU Colony Forming Units CLSI Clinical and Laboratory Standards Institute CoA Certificate of Analysis DD/MM/YYYY Date / Month / Year EUCAST European Committee on Antimicrobial Susceptibility Testing H2SO4 Sulphuric acid I Intermediate IATA-DGR International Air Transport Association - Dangerous Goods Regulations IQC Internal Quality control M/Q water Milli Q water MCT Microcentrifuge tube Mg Milligram mL Milliliter MHA Mueller Hinton Agar MHB Mueller Hinton Broth MIC Minimum Inhibitory Concentration NARS-Net National AMR Surveillance Network NCDC National Centre for Disease Control NS Non-Susceptible OSBF Other Sterile Body Fluids QC Quality Control R Resistant S Susceptible SDD Susceptible Dose-Dependent SOP Standard Operating Procedure TSA Tryptic Soya agar TSB Tryptic Soya Broth UN Unit VAS Vancomycin Agar Screen µg Microgram µl Microliter | 414 | definition | 1.000 | https://ncdc.mohfw.gov.in/uploads/pdf/amr9.pdf |
| What does the broth microdilution method assess for aerobic Gram-negative bacterial isolates? | in vitro susceptibility to Colistin | National Centre for Disease Control, India Objectives & Scope This SOP describes the standard broth microdilution method used to determine the in vitro susceptibility to Colistin for aerobic Gram-negative bacterial isolates in Clinical Microbiology laboratory. It addresses the preparation of Cation adjusted Mueller Hinton Broth (CAMHB) and colistin stock solution for dilution tests, testing conditions (including inoculum preparation, use of selective quality control (QC) strains, incubation time, and temperature), determining minimal inhibitory concentration (MIC), result analysis using approved breakpoints and QC procedures. Background As per the latest recommendations by CLSI and EUCAST, broth microdilution method should be used to quantitatively measure colistin’s in vitro activity against aerobic Gram-negative bacterial isolate. | 143 | definition | 1.000 | https://ncdc.mohfw.gov.in/uploads/pdf/amr9.pdf | National Centre for Disease Control, India Objectives & Scope This SOP describes the standard broth microdilution method used to determine the in vitro susceptibility to Colistin for aerobic Gram-negative bacterial isolates in Clinical Microbiology laboratory. |
| What does the interpretive category 'Non-susceptible (NS)' mean in antimicrobial susceptibility tests? | organisms have only a susceptible interpretive category, not an intermediate or resistant one | It implies a) clinical efficacy in body sites where the drugs are physiologically concentrated (e.g. quinolones in urine) or b) at sites where the drug is not explicitly concentrated, clinical efficacy at a higher-than- normal drug dosage (e.g. β-lactams). • Resistant (R) isolates are not inhibited by the usually achievable concentrations of the agent or demonstrate zone diameters that fall in the range where specific microbial resistance mechanisms (e.g., β-lactamases) are likely, and infection is not expected to respond to treatment with the highest recommended doses. • Non-susceptible (NS) organisms have only a susceptible interpretive category, not an intermediate or resistant one. A susceptible-only interpretive category may be applied to new antimicrobial agents for whom no resistant isolates have been encountered when initial interpretive criteria are determined. | 600 | definition | 1.000 | https://ncdc.mohfw.gov.in/uploads/pdf/amr9.pdf | • Non-susceptible (NS) organisms have only a susceptible interpretive category, not an intermediate or resistant one. |
| What does the term 'Minimal inhibitory concentration (MIC)' refer to? | the lowest concentration of an antimicrobial agent that prevents visible growth of a microorganism in an agar or broth dilution susceptibility test | Isolates that test with a MIC above the susceptible interpretive breakpoint are considered non-susceptible. • SDD – Susceptible Dose-Dependent Category in which the susceptibility of antibiotics against an organism depends on the treatment regimen dosage. Minimal inhibitory concentration (MIC) – the lowest concentration of an antimicrobial agent that prevents visible growth of a microorganism in an agar or broth dilution susceptibility test. | 297 | definition | 1.000 | https://ncdc.mohfw.gov.in/uploads/pdf/amr9.pdf | Minimal inhibitory concentration (MIC) – the lowest concentration of an antimicrobial agent that prevents visible growth of a microorganism in an agar or broth dilution susceptibility test. | 50 | page=50,block=1 | 0.700 | valid |