L1.Microbial Path Intro Flashcards
(23 cards)
Distinguish between Colonization, Infection, and Disease?
Colonization: a bacterium enters a body, finds a niche and persists in the particular site.
Infection: A bacterium which is CAPABLE of causing a disease becomes established in the body.
Disease: Is an infection that produces symptoms.
What is a PRIMARY INFECTION?
Infection caused by exogenous pathogens (an organism not normally found in healthy humans).
Note: also referred to as an EXOGENOUS Infection
What is an OPPORTUNISTIC INFECTION?
An infection caused by generally “NORMAL FLORA.”
Note: Also referred to as an ENDOGENOUS Infection
What are two problems that prevent Koch’s postulates from being useful in all cases?
- Can’t culture all bacteria in lab
2. Sometimes can’t reproduce disease in Animal
How is Koch’s Postulate changed in its MOLECULAR VERSION?
- The disease should be significantly associated w/ a specific GENE found in the strains of bacteria that cause the disease.
- Activating/Inactivating this GENE should increase/decrease the Virulence. Additionally, introduction of a cloned GENE into an avirulent strain should render the strain virulent.
- GENE must be Expressed by bacterium when in human/animal with disease.
Of the 4 major groups of microorganisms, Gram+ cocci & rods and Gram- cocci & rods, what are the two that most frequently cause human disease?
- Gram Positive Cocci
2. Gram Negative Rods
What type of bacteria is Mycobacterium tuberculosis? What disease does it cause?
It is an acid-fast bacteria that causes TB
What disease does the bacterium Carynebacterium diptheriae cause? Through what mechanism is the disease contracted? Is it a threat in developed countries?
C. ditheriae causes Diptheria disease. Diptheria is an upper respiratory tract infection that is no longer a threat in developed countries due to well developed/effective vaccinations.
What type and shape of bacteria is C. diptheriae?
A Rod (Club) shaped gram positive bacteria
After a 2-6 day incubation period Diptheria expresses very similarly to a common cold. However, after awhile breathing obstruction, irregular heartbeat and coma may occur. What is the cause of the more serious affects of a C. diptheriae infection?
- Breathing obstruction is caused by PSEUDOMEMBRANE FORMATION.
- Irregular heartbeat and coma are caused by the Diptheria TOXIN (DT) produced by the C. diptheriae.
How is toxic domain A of Dipetheria Toxin able to separate from the rest of the toxin after it is translocated accross the membrane by the T domain.
PROTEOLYTIC NICKING: the A and B domains are held together by a disulfide bond that is broken via a reduction reaction.
What is the function of the B-domain of Diptheria Toxin (DT)? How could this be used in cancer therapies?
The job of the B-domain in DT is to bind to protein receptors on the outside of cell membranes and get the DT endocytosed into the cell. If you could get a B-domain that specifically targeted cancer cell you could deliver the toxic A-domain to cancer cells but not others.
What are the 3 methods of treatment for Diptheria?
- Anti-toxin antibodies made in horses (passive immunity).
- Antibiotics - penicillin or erythromycin
- Vaccination - DPT
What portion of the DPT vaccine target C diptheriae bacteria? Is it effective?
The D part = Diptheria Toxoid - toxin inactivated with formaldehyde. Very Effective & safe. 4 shots b4 2 yr –> resistant for life
Bordetella pertussis causes what disease? What is the type and shape of the B. pertussis?
B. pertussis is a small, GRAM-, strictly aerobic ROD that causes WHOOPING Cough.
How is B. pertussis acquired? What type of infection occurs?
Inhalation –> respiratory infection.
What are the main symptoms of whooping cough?
Repetitive coughing with ‘whoops’. Cough lasts for a very long time.
What portion of the DPT vaccine treats whooping cough? What is potential problem with it?
The P portion = Pertussis - heat killed Bordetella pertussis. B/c it isn’t just the toxin and it is actually killed B. pertussis may cause minor fever and in very rare cases brain damage.
How does B. pertussis avoid the immune defense of mucus and cilia removal?
B. pertussis binds specifically to Cilia with ADHESINS.
What are the two Adhesins produced by B. pertussis? Describe briefly.
- Filamentous Hemagglutinin (Fha) - forms filamentous structure on the cell surface.
- Pertussin Toxin (Ptx) - Has 6 subunits (S1-S5 w/ 2 S4s).
Describe the roles of the 6 Pertussin toxin (Ptx) subunits.
S2 & S3 mediate the binding
S4s provide conformational change and move S1 subunit into cytoplasm of cell
S1 is the toxic portion of Ptx.
By what mechanism does the S1 subunit of Ptx cause toxicity?
S1 acts in a very similar manner to the A-domain of Diptheria toxin. It causes ADP ribosylation, modifying cellular proteins. But target is different. S1 targets a G-protein stopping the regulation of cAMP –> high levels of cAMP.
What are the 2 methods of treatment of whooping cough?
- Antibiotics - Doesn’t actually benefit patient but stops further infection and spread of pertussis to others. Erythromycin.
- Vaccination - DPT
