Micro Lec 4

Question 1

Viruses and Cancer

Answer 1

Viruses play a role in cancer because of uncontrolled growth. Example Hepatitis B cause liver cancer, Human Papilloma Virus (HPV) causes cervical virus. Cancer is found in 5% of people with HIV. 90% of women with HPV are disease free correlation doesn’t equal causation.

Question 2

Virulence

Answer 2

An ability of a microorganism to produce disease and there are 2 basic mechanisms of virulence which are Invasion of host and toxin production.

Question 3

Factors involved in determining virulence

Answer 3

Microbial physiology, Specific Adherence, Avoiding Antimicrobial Defences, # of microbes, Invasion of Cells , and Toxin production.

Question 4

Microbial physiology

Answer 4

Is the pathogens physiology compatible with a particular host environment. Example is anaerobic vs aerobic conditions

Question 5

Specific Adherence

Answer 5

Requires adhesins on microbe interacting with specific receptor on host cells surface. Example of possible adhesins are capsule, fimbriae, flagella, and cilia

Question 6

Avoiding Antimicrobial Defences

Answer 6

1) Capsules- prevents engulfment by phagocytes. 2) Flagella- prevents phagocytosis by lymphocytes.3) Antigenic variations- cannot be recognize by hosts antibody response. 4) Antibiotic Resistance- some bacterial strains have a specific gene in which growth still occurs in the presence of a particular antibiotic, occurring more because of overuse of antibiotics. 5) Secretion of enzymes/ proteins Example is coagulases which forms blood clot that surrounds and protects bacterium.

Question 7

of microbes

Answer 7

ID50 - dose amount of microbes required to infect 50% of sample population. Different for each microbe. Higher the ID 50 the less infectious, the less ID50 the more infectious. At a particular cell density certain microbes secrete toxins via quorum sensing.

Question 8

Invasion of Cells

Answer 8

Some bacteria also invade and reproduce inside cells, typical of viruses. An example is Mycobacterium tuberculosis invade epithelial cells of the lung.

Question 9

Toxin production

Answer 9

2 types of toxins are exotoxin and endotoxin. LD50- dose of toxin required to kill 50% of a sample population (lethal dose)