Antimicrobial Susceptibility Testing and Antibiotic Resistance Detection
Updated: Sep 5
https://doi.org/10.66715/cerebral-link/2026.v4.c7.6686 | Cerebral Link | Publish by Cerebral Publication Private Limited | 2026 | Volume 4 | Page 66-86 |ISBN: 978-81-689463-6-1 | Book Title: - Text-book of Practical Microbiology | Chapter 7: Antimicrobial Susceptibility Testing and Antibiotic Resistance Detection
Mahendra Pratap Swain, Department of Pharmaceutical Sciences and Technology, Birla Institute of Technology, Mesra, Ranchi, Jharkhand, India - 835215
Abstract
Antimicrobial susceptibility testing (AST) is an essential component of clinical microbiology that determines the response of pathogenic microorganisms to antimicrobial agents and supports the selection of appropriate therapy. The increasing global burden of antimicrobial resistance (AMR) has further emphasized the importance of accurate, standardized, and timely laboratory detection of resistant organisms. This chapter provides a comprehensive overview of the principles, methodologies, interpretation, and quality-control requirements of antimicrobial susceptibility testing and resistance detection. Conventional methods, including the Kirby–Bauer disk diffusion technique, broth and agar dilution methods, minimum inhibitory concentration (MIC) determination, and gradient diffusion tests, are discussed along with their practical applications. Automated susceptibility testing systems and rapid diagnostic approaches are also introduced to demonstrate their role in improving laboratory efficiency and reducing turnaround time. Interpretation of susceptibility results according to recognized standards, including susceptible, intermediate or susceptible with increased exposure, and resistant categories, is emphasized. Special attention is given to laboratory detection of clinically important resistance mechanisms, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin resistance, extended-spectrum β-lactamases (ESBLs), AmpC β-lactamases, and carbapenemases. Phenotypic, biochemical, immunological, and molecular approaches for detecting specific resistance determinants are also considered. Quality control, standardized inoculum preparation, appropriate media selection, incubation conditions, biosafety, and common sources of technical error are highlighted. Effective application of AST and resistance-detection methods is crucial for antimicrobial stewardship, infection prevention, surveillance of resistance patterns, and improved patient outcomes.
Keywords: Antimicrobial Susceptibility Testing, Antibiotic Resistance, AMR, MIC, Kirby–Bauer Method, ESBL, MRSA, Carbapenemase, Antimicrobial Stewardship.
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