Testing for mechanisms of resistance

Introduction

In this module you will learn about phenotypic and genotypic laboratory techniques that are used to test for common mechanisms of antimicrobial resistance (AMR). World Health Organization (WHO) priority pathogens for surveillance in human health, and pathogens subject to surveillance and monitoring as described by the World Organization for Animal Health (OIE) and the Food and Agriculture Organization for the United Nations (FAO) are considered in some detail. You were introduced to these pathogens in the Isolating and identifying bacteria module.

You will start by looking at resistance patterns of global concern in human and animal health, and the importance of knowing the underlying resistance mechanism involved. You will further learn how data derived from screening for specific resistance mechanisms and confirmatory testing, differs from antimicrobial susceptibility testing (AST) data, and the role it plays in AMR surveillance. At a more practical level you will study the principles and applications of relevant laboratory techniques using wellcharacterised examples, such as carbapenemase-producers, methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum beta-lactamase (ESBL)-producers. Examples of resistance mechanisms directly relevant to your work and quality control (QC) measures related to these techniques will also be raised.

Basic knowledge of concepts such as the emergence and spread of ‘resistance genes’ will be assumed. If you are unfamiliar with these concepts or would like a refresher course, you might want to look back at the Introducing antimicrobial resistance module or these free online courses: Understanding antibiotic resistance [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] and Inheritance of characters

By the end of this module you should be able to:

  • give examples of the resistance patterns/resistant organisms causing global concern
  • give examples of the resistance patterns/resistant organisms encountered in your work
  • understand the difference between screening and confirmatory testing
  • describe some of the phenotypic methods commonly used for screening and confirmation of resistance mechanisms
  • understand how genotypic methods can be used, and the advantages/disadvantages of genotypic versus phenotypic methods
  • understand how more data from detailed testing for resistance mechanisms/genes contributes to AMR surveillance
  • apply your knowledge of these laboratory tests to interpret data relevant to your work
  • know the importance of procedures designed to ensure the quality of these laboratory tests in your workplace.

Activity 1 Assessing your skills and knowledge

Before you begin this module, think about your current level of knowledge and skills in the areas covered in this module. You will have an opportunity to repeat this activity when you have completed the module. Do not worry if you lack confidence in some areas, they may be knowledge areas and skills that you are hoping to develop by studying this module. For areas where you feel fully confident, it is always a good idea to refresh and update knowledge and skills.

Use the interactive tool to rate your confidence in these areas using the following scale:

  • 5 Very confident
  • 4 Confident
  • 3 Neither confident nor not confident
  • 2 Not very confident
  • 1 Not at all confident

This is for you to reflect on your own knowledge and skills you already have.

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1 Resistance problems of global concern