Antimicrobial Resistance
Antimicrobial resistance (AMR) is the ability of microorganism (bacteria, viruses, fungi,
parasites) to survive and grow despite the presence of drugs that were previously effective
against them.
Normally: Antibiotic → kills bacteria
In AMR: Antibiotic → no effect
Bacteria survive and continue infection.
▪ Why AMR Happens?
Inside bacteria:
➢ There are genes and proteins that antibiotics target.
Bacteria can:
➢ Mutate (change their genes)
➢ Acquire resistance genes from other bacteria.
Epidemiology / Global Burden of AMR:
▪ Antimicrobial resistance is a global public health threat.
▪ WHO reports millions of infections yearly due to resistant bacteria.
▪ Increasing mortality and treatment failure worldwide.
▪ Higher burden in low- and middle-income countries.
▪ Common in hospitals and community infections.
Types of Antimicrobial Resistance
A. Intrinsic (Natural Resistance)
Already present in bacteria due to:
▪ Cell wall structure.
▪ Lack of drug target.
➢ Gram-negative bacteria resist some antibiotics because of outer membrane barrier.
B. Acquired Resistance
Develops later by:
, 1. Mutation:
Random genetic change
Example: change in ribosome → antibiotic cannot bind.
2. Gene Transfer
Bacteria share resistance genes through:
Conjugation → plasmid transfer
Transformation → uptake of DNA
Transduction → via bacteriophage
▪ This spreads resistance very fast
Mechanisms of Resistance
1. Enzyme Inactivation
▪ Bacteria produce enzymes that destroy antibiotics.
▪ Example: Beta-lactamase breaks penicillin and cephalosporins.
2. Target Site Modification
▪ Antibiotic cannot bind to its target.
▪ Example: MRSA modifies penicillin-binding protein.
3. Efflux Pumps
▪ Bacteria actively pump antibiotic out.
▪ Drug concentration becomes too low to work.
4. Reduced Permeability
▪ Drug cannot enter the bacterial cell.
▪ Common in Gram-negative bacteria.
5. Metabolic Bypass
▪ Bacteria use alternative pathway.
▪ Example: Resistance to sulfonamides.
Antimicrobial resistance (AMR) is the ability of microorganism (bacteria, viruses, fungi,
parasites) to survive and grow despite the presence of drugs that were previously effective
against them.
Normally: Antibiotic → kills bacteria
In AMR: Antibiotic → no effect
Bacteria survive and continue infection.
▪ Why AMR Happens?
Inside bacteria:
➢ There are genes and proteins that antibiotics target.
Bacteria can:
➢ Mutate (change their genes)
➢ Acquire resistance genes from other bacteria.
Epidemiology / Global Burden of AMR:
▪ Antimicrobial resistance is a global public health threat.
▪ WHO reports millions of infections yearly due to resistant bacteria.
▪ Increasing mortality and treatment failure worldwide.
▪ Higher burden in low- and middle-income countries.
▪ Common in hospitals and community infections.
Types of Antimicrobial Resistance
A. Intrinsic (Natural Resistance)
Already present in bacteria due to:
▪ Cell wall structure.
▪ Lack of drug target.
➢ Gram-negative bacteria resist some antibiotics because of outer membrane barrier.
B. Acquired Resistance
Develops later by:
, 1. Mutation:
Random genetic change
Example: change in ribosome → antibiotic cannot bind.
2. Gene Transfer
Bacteria share resistance genes through:
Conjugation → plasmid transfer
Transformation → uptake of DNA
Transduction → via bacteriophage
▪ This spreads resistance very fast
Mechanisms of Resistance
1. Enzyme Inactivation
▪ Bacteria produce enzymes that destroy antibiotics.
▪ Example: Beta-lactamase breaks penicillin and cephalosporins.
2. Target Site Modification
▪ Antibiotic cannot bind to its target.
▪ Example: MRSA modifies penicillin-binding protein.
3. Efflux Pumps
▪ Bacteria actively pump antibiotic out.
▪ Drug concentration becomes too low to work.
4. Reduced Permeability
▪ Drug cannot enter the bacterial cell.
▪ Common in Gram-negative bacteria.
5. Metabolic Bypass
▪ Bacteria use alternative pathway.
▪ Example: Resistance to sulfonamides.
