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Definitions of antibiotic resistance

A Multiple Drug Resistance bacterium is defined as a bacterium that is resistant to at least three different categories or classes of antibiotics.
A three-dimensional (3d) computer-generated image of a group of methicillin-resistant Staphylococcus aureus (MRSA) bacteria, which were arranged in a cluster. The artistic recreation was based upon scanning electron microscopic (SEM) imagery
© U.S. Centers for Disease Control and Prevention - Medical Illustrator
According to the European Centre for Disease Prevention and Control, a Multiple Drug Resistance (MDR) bacterium is defined as a bacterium that is resistant to at least three different categories or classes of antibiotics.

An infection caused by an MDR bacterium can be challenging to treat. However, there are bacteria that are even more resistant to the clinically useful antibiotics that we depend on.

An infection caused by an EXtensively Drug Resistant (XDR) bacterium is only treatable, and the bacterium can only be destroyed, by only two different classes of antibiotics.

But most worryingly of all, we now have Pan-Drug resistant (PDR) bacteria that are resistant to all antibiotics.

© University of East Anglia
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Using Infection Control to Combat Antimicrobial Resistance

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