Antibiotic Resistance


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•  Evolution of antibiotic resistance in bacteria

Antibiotics are chemicals produced by microbes that either kill (bactericidal) or inhibit the growth (bacteriostatic) of bacteria

  • Antibiotics are commonly used by man as a treatment for bacterial infections (not effective against viral infections)

In a bacterial colony, over many generations, a small proportion of bacteria may develop antibiotic resistance via gene mutation

  • When treated with antibiotics, the resistant bacteria will survive and reproduce by binary fission (asexual reproduction)
  • The antibiotic resistant bacteria will flourish in the absence of competition from other strains of bacteria (killed by antibiotic)
  • Antibiotic resistant bacteria may also confer resistance to susceptible strains by transferring plasmids via bacterial conjugation
  • The introduction of antibiotic (selection pressure) has caused the antibiotic resistance gene to become more frequent (evolution)

An example of antibiotic resistance in bacteria can be seen in the evolution of Staphylococcus aureus (Golden staph)

  • Golden staph can cause infections to the skin (lesions and boils) as well as more serious infections (pneumonia, meningitis)
  • Historically, these infections were treated using the antibiotic methicillin 
  • Bacterial strains developed that were resistant to this antibiotic (methicillin-resistant Staphylococcus aureus – or MRSA)
  • These strains proliferated while susceptible strains died out (methicillin-sensitive Staphylococcus aureus – or MSSA)
  • MRSA infections are now especially present in hospitals and nursing homes, where the use of methicillin was most common
  • Medical practitioners now prescribe alternate antibiotic agents to treat infections caused by Staphylococcus aureus

Antibiotic Resistance in Bacteria

antibiotic resistance