How can bacteria become resistant to antibiotics?

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How can bacteria become resistant to antibiotics?

We have already discussed the idea that some bacteria have always been resistant to certain antibiotics and that each antibiotic only has an effect on specific germs (See the antimicrobials section). But sometimes bacteria can become resistant to antibiotics that previously killed or damaged them. This resistance can develop in the following ways:
  • A random change in the genetic material of the bacteria, this is known as a mutation. This can cause the genetic material to make the bacteria resistant to harm by the drug.
  • By 'picking up' genetic material that contains instructions that code for antibiotic resistance. This genetic material can come from viruses, other bacterial cells or plasmids, which are loops of DNA in a bacterial cell that are separate from its chromosome (bacteria only have one single chromosome, unlike us humans who have 23 pairs in each cell). These plasmids can move from bacteria to bacteria, picking up and depositing bits of genetic material as they go. If the plasmid contains a bit of genetic material that codes for antibiotic resistance this can be spread to many other bacteria.

    So this explains how antibiotic resistance can develop but it doesn't explain what effect these genetic instructions have on stopping the antibiotic from harming the bacteria. They can do this in a number of ways:
    • Inactivating the antibiotic before it reaches the bacterial cell
    • Reducing the uptake of the antibiotic into the bacterial cell
    • Increasing the amount of antibiotic that is pumped out of the bacterial cell
    • Altering the antibiotic's target on the bacterial cell so that the antibiotic cannot recognise and target the cell
    • Activating different ways of multiplying, feeding, maintaining its structure etc, so that it can function despite the effect of the antibiotic (See the antimicrobials section for an overview of how antibiotics can interfere with a bacteria's life processes)

Related Resources
AWARE (Alliance Working for Antibiotic Resistance Education)
When the Antibiotics Quit Working...
Antimicrobial Resistance
Alliance for the Prudent Use of Antibiotics (APUA) Website
Antibiotics: A fading wonder
Promoting Appropriate Antibiotic Use in the Community
Antimicrobial Resistance Webpages
The Real Millennium Bugs
Antibiotic resistance factsheet for schools
Bacterial Resistance to Antibiotics
Antibiotic Resistant Germs
The Microbial Threat
The Path of Least Resistance
The Complete Idiot's Guide to Dangerous Diseases & Epidemics
Overcoming Antimicrobial Resistance
Factsheet - Antimicrobial Resistance
Resistance to Antibiotics & Other Antimicrobial Agents
The facts about Vancomycin-resistant enterococci
OMNI Resources about Antimicrobial Resistance
The Bug Investigators
Improving antibiotic prescribing is an urgent priority - how low can we go?
Interventions to improve antibiotic prescribing practices for hospital inpatients (Cochrane Review)
Interventions to improve antibiotic prescribing in ambulatory care (Cochrane Review)

Date of Posting: 10/01/2003
Date of next Review: 07/01/2005

Related Questions:
What is Antimicrobial Resistance?
Do people become resistant to antibiotics?
Why is antimicrobial resistance a health problem?
Is antimicrobial resistance only a problem in the UK?
How will my doctor treat my infection if one antibiotic doesn't work?
How can I help and when should I take antibiotics?

MeSH keywords:
Drug Resistance, Bacterial; Drug Resistance, Microbial; Bacteria

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