1. Bacteria and Disease
Biotechnology

2. Essential Questions How are bacteria that cause disease identified?
What are two mechanisms bacteria use to cause disease?
What is an antibiotic and how does antibiotic resistance develop?
Essential Questions

3. Pathogen – microorganism that causes disease in a plant, animal, or insect
Pathogenicity – ability to produce disease in host organism
Virulence – degree of pathogenicity by the microbe
Key Terms

4. Disease Human disease- about one-half caused by bacteria
Many pathogens opportunistic;
Wait for immune system to become weakened
Allow normal bacteria flora to become pathogenic.
Example Streptococcus pneumoniae
Disease

5. Significant contributions to fighting disease
Louis Pasteur, Joseph Lister and others
Linked pathogenic microbes to disease in late 1800’s
Robert Koch
First to make connection between certain bacteria and disease
Significant contributions to fighting disease

6. Four criteria used to establish a specific pathogen causes the disease
Same pathogen in each reported case of the disease
Isolate the pathogen and grow it in a pure culture
Use culture pathogens to induce the disease in an experimental animal
If animal becomes sick, isolate the same pathogen from the diseased animal
Koch’s Postulates

7. Mechanism for causing disease –two types
Invasiveness –
Pathogen grows and invades tissue which disrupts the physiology of the host
Toxingenesis
Production of a toxin
Mechanism for causing disease –two types

8. Invasiveness Ability to invade tissue dependent on
(1) Colonization – establishment of pathogen at the site of entry
Usually inhabit regions exposed to external environment
Sites of entry include
Urogenital tract
Digestive tract
Respiratory tract
Invasiveness

9. Invasiveness (2) Adherence (cont.)
Specificity of adherence determine by
Tissue preference- type of tissue determines attachment
Ex. S. mutans abundant in dental plaque but not on surfaces of tongue
Species specificity – only infect certain animal, plant or insect species
Ex. E.coli K-88 only infects pigs not humans
Invasiveness

10. Invasiveness (3) Invasion
Ability to bypass or overcome host defense mechanisms
Can happen by bacteria secreting extracellular substances that breakdown primary or secondary defenses of the host
Extracellular substances commonly referred to as invasins
Invasiveness

11. Toxigenesis Production of toxins Two types of bacterial toxins
Lipopolysaccharides – macromolecule composed of lipids and carbohydrates
Associated with cell walls of gram negative bacteria
Proteins
Commonly released into the extracellular environment by pathogenic bacteria
Toxigenesis

12. Bacterial Toxins Further classified as
Endotoxins – toxin associated with the bacterial cell
Exotoxins – toxins released from growing bacterial cells and cells broken open by host defense mechanisms
Bacterial Toxins

13. Exotoxin Produced chiefly by gram positive bacteria
Can cause the disease without the bacteria present; toxin is enough
Among the most potent poisons known
Example:
Cholera caused by vibrio cholerae – toxin causes severe diaherra
Scarlet fever caused by Streptococcus pycogenes – toxin causes localized rash
Exotoxin

14. Cholera

15. Toxic component of outer membranes of some gram-negative bacteria
Induces general symptoms of fever and aches
Example: Salmonella typhi (typhoid fever) and other species of salmonella that causes food poisoning
Endotoxin

16. Salmonella

17. People dying from bacterial diseases has declined Why?
Improved sanitation measures
Development of antibiotics
People dying from bacterial diseases has declined Why?

18. Type of medication that destroy or slow down the growth of bacteria
Comes from two greek words meaning “against life”
Example of antibiotic is penicillin
works by inhibiting the synthesis of bacteria’s cell wall
causes cell to pop when they grow in size
Antibiotic

19. Development of Antibiotic Resistance-Why?
Drug companies not developing new antibiotics
Antibiotics over prescribed
Patients do not complete prescription
Use of antibiotics in livestock that get in our food supply.
Development of Antibiotic Resistance-Why?