Bacteria and Disease Biotechnology

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

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

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

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

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

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

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

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

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

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

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

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

Cholera

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

Salmonella

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

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

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?