Methods and Applications

From Pharmacotherapy

Antimicrobial Susceptibility Testing: A Primer for Clinicians

Kristi M. Kuper, Pharm.D.; Deborah M. Boles, M.S.; John F. Mohr, Pharm.D.; Audrey Wanger, Ph.D.

Posted: 11/17/2009; Pharmacotherapy. 2009;29(11):1326-1343. © 2009 Pharmacotherapy Publications

Download article in full


Appropriate use of antimicrobials in health care continues to be a challenge. Reliable and reproducible antimicrobial susceptibility testing methods are necessary to provide the clinician with valuable information that can be translated into positive clinical outcomes at the bedside. However, there are nuances with these testing methods that, if unrecognized, could lead to misinterpretation of results and inappropriate antibiotic selection. This primer describes the common antimicrobial susceptibility tests used in the clinical microbiology laboratory and reviews how subtle differences in testing methods and technique can influence reported results. Clinicians who have a thorough understanding of qualitative and quantitative methods, automated susceptibility testing systems, and commonly used screening and confirmatory tests for antibiotic-resistant organisms can strengthen institutional antibiotic stewardship programs and improve patient outcomes.


In January 2007, the Infectious Diseases Society of America, in conjunction with the Society for Healthcare Epidemiology, released guidelines for developing an institutional program to enhance antimicrobial stewardship.[1] These guidelines underscore the need for accurate and reproducible identification of microorganisms and antibiotic susceptibilities. This is integral to the care of patients with infectious diseases and plays a critical role in antimicrobial stewardship and epidemiologic investigations.

The clinician who has an advanced knowledge of antimicrobials, coupled with an understanding of commonly used microbiology testing methods, can be effective in improving antimicrobial utilization and optimizing patient care. These skills are particularly relevant today and can help combat increased antimicrobial resistance in the hospital and community settings. The purposes of this review are to help pharmacists gain a basic understanding of common antimicrobial susceptibility tests used in the clinical microbiology laboratory, and to demonstrate how differences in testing can influence therapeutic choices for treating infectious diseases.

How Effective are our Phenotypic Methods in Detecting Antimicrobial Resistance ?
Other alternatives ?
Molecular Characterization of Microorganisms ?
 Which method is the “Gold Standard” for Antimicrobial Resistance Detection ? –
Phenotypic Methods
Molecular or genotypic tests
Download PDF Presentation:
Phenotypic and Genotypic Methods and Antimicrobial Resistance
  EUCAST MIC and Zone diameter distributions of wild type microorganisms

Database January 2010: >20 000 distributions

Click here to go directly to the program!

Should you have problems when accessing the website – please send a mail to or

Click here to go directly to the program!

Antimicrobial wild type distributions of microorganisms


Method: MIC?
Disk diffusion
CDS Antimicrobial Susceptibility Testing – Feb 2010

Implementation of EUCAST breakpoints and AST 2010-2011

January 27, 2010

Implementation of EUCAST breakpoints and AST 2010-2011

Interpretative Reading of Antibiogram

 By Luis Martinez- Martinez

Service of Microbiology

University Hospital Marqués de Valdecilla

Download PDF Presentation:


%d bloggers like this: