1. Evolution of Resistance to Antibiotics in Bacteria Presented by Jana Boozer Katelin Erwin Ashley Gregory Sara Thompson HUMANS & NATURE:

2. What is antibiotic resistance? • Antibiotic resistance occurs when an antibiotic has lost its ability to effectively control or kill bacterial growth; in other words, the bacteria are "resistant" and continue to multiply in the presence of therapeutic levels of an antibiotic.

3. Why do bacteria become resistant to antibiotics? • When antibiotics are used to kill the bacterial microorganisms, a few microorganisms are able to still survive, because microbes are always mutating, eventually leading to a mutation protecting itself against the antibiotic

4. Antibiotics that are used correctly overwhelm the harmful bacteria • Overuse of antibiotics or unnecessary use creates a selective environment • Resistant bacteria has better fitness in this context • Resistant strains survive and multiply. • After reproducing, the resistant bacteria move to another host.

5. How humans have created the upsurge of bacterial diseases: • International travel • Inadequate sanitation • “antibiotic paradox”

6. How do bacteria become resistant? Bacteria can gain resistance over time through: • Acquired resistance • Vertical gene transfer • Horizontal gene transfer

7. Acquired Resistance • Mechanisms are developed by bacteria in order to acquire resistance • Either modification of existing genetic material or acquisition of new genetic material from another source. • Development of resistance through spontaneous mutation is called primary resistance. • Errors in DNA synthesis during replication • Occasional failures in the DNA repair systems

8. Vertical Gene Transfer • Resistant genes are developed • Genes directly transferred to progeny during DNA replication • This is directly related to Darwin’s theory of evolution.

9. Horizontal Gene Transfer (HGT) • “lateral gene transfer” • Genetic material is contained in small packets of DNA. • Packets can be transferred between individual bacteria of the same species or different species.

10. 3 Mechanisms of HGT • Transduction • Transformation • Penicillin-resistant gonorrhea • Conjugation • In 1968, 12,500 people in Guatemala died of Shigella diarrhea epidemic.

11. Spread of Resistant Bacteria • Rapid growth of bacteria • Small size • Simple internal structure • Multiply rapidly • New generation in as little as 20 minutes

12. Strategies to delay widespread antibiotic resistance: • Don’t use antibiotics to treat viruses or viral infections. • Avoid mild doses of antibiotics over a long period of time. • When treating a bacterial infection with antibiotics, take all the pills. • Use a combination of drugs to treat bacterial infections • Reduce/eliminate “preventive” use of antibiotics on livestock and crops.

13. Evolutionary theory: • Given time, heredity, and variation, any living organism will evolve when a selective pressure is introduced

14. Benefit/Cost • Benefit • In presence of antibiotics, being resistant benefits bacteria. • Cost • Resistant genotypes are less fit than sensitive counterparts in the absence of antibiotics

15. Can bacteria lose their antibiotic resistance? • Antibiotic resistance traits can be lost • Occurs more slowly • Selective pressure is removed • Bacterial population can potentially revert to a population of bacteria that responds to antibiotics.

16. With more research, education of the public, and well thought out regulations, the problems can be solved. Several strategies are currently used to find new antibacterial compounds and new strategies are in development and trial.

17. Sources http://evolution.berkeley.edu/evosite/relevance/IA1antibiotics.shtml http://www.fda.gov/Fdac/features/795_antibio.html http://www.pbs.org/wgbh/evolution/library/10/4/l_104_03.html http://www.scq.ubc.ca/attack-of-the-superbugs-antibiotic-resistance/ http://www.textbookofbacteriology.net/resantimicrobial.html http://www.tufts.edu/med/apua/Q&A/Q&A_AR.html