2. Pathogenic Bacteria Pathogen: disease-causing microorganism

3. Pathogenic Bacteria What are two ways that pathogenic bacteria cause disease? 1) They damage and destroy tissues when they secrete digestive enzymes to break down cells to use as food eg: streptococci (Streptococcus sp.) causes a painful sore throat referred to as strep throat

4. Pathogenic Bacteria What are two ways that pathogenic bacteria cause disease? 2) They release toxins that travel throughout the body interfering with normal activity eg: tetanus (Clostridium tetani) enters through contaminated wounds and secretes a toxin that interferes with nerve synapses

5. Pathogenic Bacteria What is an antibiotic? A drug that fights bacteria by interfering with their cellular functions eg: Penicillin - interferes with bacterial cell-wall synthesis eg: Tetracycline - interferes with bacterial protein synthesis

6. Pathogenic Bacteria What is antibiotic resistance? bacteria have developed resistance to many antibiotics, and many diseases that were once easy to treat are now more difficult to treat. antibiotic resistance results from the over-use of antibiotics example of classic Darwinian evolution by natural selection

7. How Antibiotic Resistance Develops 1)A population of bacteria is exposed to an antibiotic - most are susceptible and die 1

8. How Antibiotic Resistance Develops 1)A population of bacteria is exposed to an antibiotic - most are susceptible and die 2)A few mutant bacteria are resistant to the antibiotic – they survive 1 2

9. How Antibiotic Resistance Develops 1)A population of bacteria is exposed to an antibiotic - most are susceptible and die 2)A few mutant bacteria are resistant to the antibiotic – they survive 3)If the antibiotic is continued for the full course of treatment, all the bacteria will die 1 2 3

10. How Antibiotic Resistance Develops 1)A population of bacteria is exposed to an antibiotic - most are susceptible and die 2)A few mutant bacteria are resistant to the antibiotic – they survive 3)If the antibiotic is continued for the full course of treatment, all the bacteria will die 4)If the antibiotic is discontinued too soon, the resistant population survives and reproduces, creating a population of antibiotic-resistant bacteria. 1 2 3 4