Overview of antibacterial susceptibility testing
- Sarah E Turbett, MD
Sarah E Turbett, MD
- Instructor in Medicine
- Harvard Medical School
- Virginia M Pierce, MD
Virginia M Pierce, MD
- Instructor in Pathology
- Harvard Medical School
The clinical microbiology laboratory serves as a valuable ally to clinicians in the diagnosis and treatment of infectious diseases. In particular, the isolation of bacteria from clinical samples yields information that can be used to guide the selection of appropriate antibiotic regimens based on knowledge of the most likely susceptibility profile of certain bacterial species. Through the use of in vitro antimicrobial susceptibility testing, the laboratory can specifically determine which antibiotics effectively inhibit the growth of a given bacterial isolate, allowing for targeted therapy. Antimicrobial resistance is a growing concern in both community and health care settings; as such, decisions surrounding empirical antibiotic treatment are becoming more complicated, and the importance of routine antimicrobial susceptibility testing to guide therapeutic decisions has increased.
Multiple different methods for antimicrobial susceptibility testing exist, including conventional methods, automated systems, and newer molecular techniques. Understanding these methods allows clinicians to correctly interpret susceptibility testing results reported by the clinical microbiology laboratory. In general, antimicrobial susceptibility testing methods used in clinical laboratories should:
●Provide rapid and accurate information to the clinician
●Be relatively inexpensive
●Be relatively easy to performTo continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:
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- BASIC CONCEPTS OF ANTIMICROBIAL RESISTANCE
- Intrinsic versus acquired resistance
- Constitutive versus inducible resistance mechanisms
- INDICATIONS FOR SUSCEPTIBILITY TESTING
- CONVENTIONAL METHODS
- Qualitative methods (disk diffusion/Kirby-Bauer method)
- - Performance
- - Advantages
- - Limitations
- Quantitative methods
- - Agar dilution
- - Broth dilution
- Broth (tube) macrodilution
- Broth microdilution
- - Antimicrobial gradient method
- Interpretation of results
- AUTOMATED METHODS
- METHODS TO DETECT SPECIFIC TYPES OF RESISTANCE
- Beta-lactamase testing
- Inducible clindamycin resistance testing
- High-level aminoglycoside resistance screening
- GENOTYPIC METHODS
- REPORTING SUSCEPTIBILITY RESULTS