Lab 1 introduction
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Antimicrobial susceptibility testing determines which antimicrobial agents bacteria are susceptible to in order to guide treatment decisions. Periodic testing is important because bacteria can develop resistance over time. Common testing methods include disk diffusion, dilution, and E-tests. International organizations like CLSI provide guidelines and standards for testing. Laboratories must implement quality control and quality assurance programs to ensure accurate and consistent results.
Lab 1 introduction
- 1. ANTIMICROBIAL SUSCEPTIBILITY TESTING Dr. Samira Fattah PhD in Medical Bacteriology College of Health Sciences-HMU
- 2. Antimicrobial Susceptibility Testing Why do we test antimicrobial susceptibility? • It is not enough to identify an organism. It is also necessary to know which antimicrobial agent the organism is susceptible to. • To set national & local antibiotic policies. • To test the activity of a new antimicrobial agent. • Test will assist the clinicians in choosing the drugs in the treatment of infection.
- 3. Antimicrobial Susceptibility Testing Periodic checking antimicrobial Susceptibility test is important • Antimicrobial Susceptibility testing is essential part of medical care. Bacteria have the ability to develop resistance to reused or subclinical doses, so stronger antibiotics are continually required to overcome this issue.
- 4. Methods of Antimicrobial Susceptibility Testing • Diffusion method (Qualitative methods) • Dilution method (Quantitative methods) • Diffusion and Dilution …. E- test • Mechanism – Specific tests …. Beta- Lactamase test • Automated methods • Genotypic methods
- 5. Antimicrobial susceptibility testing guidelines A number of standards and guidelines are currently available for antimicrobial susceptibility testing and subsequent interpretive criteria throughout the world published by: • Clinical Laboratory and Standards Institute (CLSI, USA) • European Committee on Antimicrobial Susceptibility Testing (EUCAST) • British Society for Antimicrobial Chemotherapy (BSAC, UK) • Comité de l’Antibiogramme de la Société française de Microbiologie (CASFM, France) • Commissie richtlijnen gevoeligheidsbepalingen (CRG, the Netherlands) • Deutsches Institut für Normung (DIN, Germany) • Japanese Society for Chemotherapy (JSC, Japan) • Swedish Reference Group for Antibiotics (SRGA, Sweden)
- 6. CLSI Documents Relating to Antimicrobial Susceptibility Tests • M2.....Disk diffusion tests • M6….. Dehydrated Mueller-Hinton agar • M7….. Broth agar dilution test-aerobes • M11…... Anaerobic dilution tests • M21….. Serum bactericidal test • M23….. Guidelines for new drug reviews • M24….. Mycobacteria and nocardia • M26….. Bactericidal activity • M27….. Antifungal tests of yeasts • M31….. Veterinary drugs and pathogens M32….. Mueller-Hinton broth M33….. Antiviral agents M38….. Antifungal tests of filamentous fungi M39….. Cumulative susceptibility reports M42….. Disk diffusion—aquatic animals M44….. Disk diffusion—yeasts M45….. Dilution and disk—fastidious bacteria M49….. Broth dilution—aquatic animals M100….. Informational supplements for M2 and M7
- 7. Selection of antimicrobial susceptibility testing methodology The selection of an AST methodology may be based on the following factors: 1. ease of performance 2. cost 3. reproducibility 4. reliability 5. accuracy 6. availability of suitable validation data for the range of organisms to be susceptibility tested
- 8. Quality control (QC) and quality assurance (QA) • Quality control/quality assurance systems should be established in laboratories performing AST • quality control refers to the operational techniques that are used to ensure accuracy and reproducibility of AST. • quality assurance includes, but is not limited to, monitoring, record keeping, evaluating, taking potential corrective actions if necessary, calibration, and maintenance of equipment, proficiency testing and training. • QC and QA program helps ensure that testing materials and processes provide consistent quality results.
- 9. Quality control (QC) and quality assurance (QA) The following components should be determined and monitored: 1. precision of the AST procedure, 2. accuracy of the AST procedure, 3. qualifications, competence, and proficiency of the laboratory personnel. 4. performance of the appropriate reagents. 5. The appropriate reference microorganism(s) should always be used and should be obtained from a reliable source for example, from the American Type Culture Collection (ATCC®).