ch 17.txt

• 35. Describe the types of symbiotic relationships seen between humans and bacteria. Give specific examples for each type of relationship.
• 1. Commensalism: One BENEFITS, Other UNAFFECTED. Ie: bacteria living on the skin of humans are not harmful or advantageous to human, but bacteria benefit by getting food and other benefits from skin.
• 2. Mutualism: Both BENEFIT. Ie: in Large Intestines: some bac synth Vit B&K, which benefit humans, while at the same time the bac has warmth and Energy source in the body.
• 3. Parasitism: One BENEFITS @ the expense of the other. Ie: E. coli in urinary tract – microorganism that if ingested can use body nutrients while harming the body (causes UTI).

• Pathogenicity: Ability for a microbe to cause a DISEASE in the host
• Virulence: The Degree of this pathogenicity (highly virulent-more likely to cause disease)
• Opportunistic Pathogen: Microbe able to cause disease ONLY when host immune system is compromised.
• Infectious Disease: Contageous diseases. Infectious dose is the minimum # of pathogens required to cause Disease SYMPTOMS. (LOWER THE ID #, the Better able to TRANSMIT disease).

• 1. Has to be able to enter host
• 2. Has to be able to overcome host defenses
• 3. Has to bring about poor physiological changes resulting in poor health
• 4. Has to exit host tissue and spread with large # to other hosts

• Acute Infection: If an organism disappears after illness
• Chronic Infection: Illness persists over long period of time
• Latent infection: Illness may reoccur(although you may not present symptoms of illness) when immune system is weak.

• 1. The same Pathogen must be present in EVERY case of the disease
• 2. Pathogen must be isolated from DISEASED host and grown in PURE culture.
• 3. This pathogen must cause the same disease symptoms when pure culture is infected into a healthy host.
• 4. This pathogen must again be isolated from the new host and shown to be IDENTICAL to the original pathogen.

• Nose: S. aureus
• Mouth & Throat: Streptococcus
• Skin: P. acnes & Staphylococcus epidermidis
• Vagina & Urethra: Streptococcus
• Large Intestines: E. coli

• ADHESINS: Allow pathogen to adhere to a cell SURFACE
• CAPSULES: Help to AVOID phagocytosis (hide from immune system)
• ANTIGENIC variation: Surface Changes that do NOT allow antibody binding (DOESN’T recognize the pathogen)

• 1. Secrete same enzyme as host secretes C3B. If that doesn’t work, step 2. ESCAPE from Phagosome: bac able to escape from phagosome before it fuses with lysosome. Som form pores to escape into cytoplasm.
• 2. Preventing Phagosome-lysosome fusion: to prevent exposure to degradative enzymes and other toxic components of lysosomes.
• 3. Surviving within phagolysosome: has capsule can delay fusion of phagosome with lysosome, allowing additional time to equip itself for growth inside this fusion.

• Acute Infection: If an organism disappears after illness
• Chronic Infection: Illness persists over long period of time
• Latent infection: Illness may reoccur(although you may not present symptoms of illness) when immune system is weak.

A host that has the pathogen, but no symptoms of the disease. The disease is then passed on and infects the people with the disease once it has been transmitted.

• ENDOTOXIN: Part of Gram – bac. Part of the OUTER membrane of Gram – bac cell wall. Can’t form a toxoid. Heat StableLipopolysaccharide triggers innate immune responseLeads to FEVER, bp drop. Small amounts can help clear infection but systemic distribution is DEADLY
• EXOTOXIN: Gram + & - bac. Synthesized in the cytoplasm of bac, may or may not be secreted. Forms toxoid. Inactivated by HEAT
• Proteins - very POTENT, some of the most potent in the world.
• IE: Cytotoxins (kill or damage host cells), Neurotoxins, Enterotoxins (affect digestive tract)
• BOTH PRODUCE: Fever, chills, weakness and Blood clots, sometimes death