General principles of microbiology Flashcards
What do viruses consist of? (3 things)
nucleic acids protected by a capsid (protein shell), and RNA or DNA
What do viruses do?
They enter cells and the divert synthetic process of those cell towards their own replication; Attach, inject nucleic acid (penetration), highjack synthetic processes inside cells to make more viruses, package, get out while going is good
viruses are the _____ and _____ group of organisms.
smallest complex
biggest simplest
biggest complex
smallest simplest
smallest simplest
Can a virus have both RNA and DNA?
no
Can viruses grow outside of a cell?
no they grow inside of them
Are bacteria prokaryotes or eukaryotes?
prokaryotes
How do bacteria look? How do they replicate?
rigid cell wall, cytoplasm, with genetic material in a circular chromosome. Binary fission.
What are eukaryotes?
unicellular and multicellular animals and plant. genetic material organised into a nucleus
What are the two categories for bacterial populations?
transient or resident
in which ways are flora important? (5)
- protect a person from infection
2.participates in metabolism - Disturbances in the ecology and balance of the normal flora may be produced by antibiotic therapy -
this is the basis of, for example, antibiotic induced diarrhea.
4.controlled by various host defense’s - normal flora in cultures may confuse the interpretation of laboratory results.
What happens if there is a disturbance with normal flora that helps to synthesize vitamin K?
there may be secondary nutritional deficiencies.
what happens if there is deficiencies in host defense’s?
may result, in some patients, in infections caused by organism that are normally not pathogenic
How does flora not harm our body?
they function as a balance eco-system with multiple species at a site no single organism predominating.
What are mycoplasmas?
Mycoplasmas are similar to bacteria but do not have the rigid cell wall, and are consequently more delicate
what types of normal flora found on the colon and the skin?
GI-tract: colon is inhabited by anaerobes and coliforms
Skin: mostly coagulase negative staphylococci
Where should there be no bacteria?
Your blood, lungs, cerebral spinal fluid, urinary tract, heart
Where and why is transient flora found?
found in a specific location often as a result of displacement of resident flora,
injury or trauma, or through human behaviour.
When do infection w/ bacteria happen?
when single species predominate a site which there is normally many species or when a single organism invades a body site that is sterile.
What determines the outcome of the body after it has had an infection caused by bacteria?
bacterial pathogenicity factors:
1. mechanical barriers
2. adherence
3. phagocytosis
4. antibodies (humoural immunity)
5. complement,
6. cell mediated immunity
7. endo/exo-toxin production.
Mechanical barriers
name?
is there bacteria?
what happens if there is a break in integrity?
-the skin
-colonized by large numbers of organisms
-allows bacteria to gain access to deeper layers
What organ is arguably the most important mechanical and innate immune system component?
the skin
What is the first requirement for bacterial invasion to occur? how?
- Adherence to the host
-ligands (small molecules) present on surface of bacteria bind to specific receptors on the mammalian cell surface
What is phagocytosis? What cells are involved?
- The ingestion of bacteria
-macrophages and blood neutrophils
What ways do bacteria’s avoid phagocytosis? example?
surround themselves with a polysaccharide capsule (a protective “coat”) and can prevent the phagocytic cell
from engulfing them.
-e.g Streptococcus pneumoniae
What ways does the host respond when bacteria’s are avoiding phagocytosis?
- produce antibodies to the capsule.
- antibody bind to (and can sometimes) alter the surface of the capsule to permits the phagocyte to take up the capsulated organism. This is referred to as opsonization
what is opsonin?
an antibody or other substance which binds to foreign microorganisms or cells making them more susceptible to phagocytosis.
what are two ways antibodies function against bacteria?
act as an opsonin or kill organisms directly
What is a complement?
complex system of plasma proteins that work together to resist bacterial infection.
Can bacteria’s be killed by complement?
Yes
what is a complement two major roles?
one on its own and one to enhance the immune response.
Cell Mediated Immunity
Some bacteria such as Mycobacterium tuberculosis and Legionella species are killed by activated
macrophages and as such cell mediated immunity is a vital defence against these organisms.
Why might a bacteria produce exotoxins? What are they?
- to damage the host
- proteins that are synthesized and released by bacteria
-may exert their effects at an anatomical location remote from the bacteria that originally synthesized them
what is a hosts defense against exotoxins
antibody
What is metastatic spread?
the distribution of an infection from primary focus of infection to a new site through the blood stream.
what happens if an organism disseminated by the blood stream?
can then cause clinical symptoms or first sign of infection at a location distant from the original infection or point of entry.
What are compromised patients?
patients deficient in some of the antimicrobial defences the body has
How are deficiencies in antimicrobial defences cause?
a disease process (for instance leukemia may give rise to a deficiency in phagocytosis) or to medical
or surgical procedures, including the administration of medication.
How would drugs cause a deficiencie?
immunosuppressive drugs to transplant patients may depress their immune system to the point where it is
no longer effective as a defence.
what are patients at risk for if they are missing
Phagocytic cells (e.g., leukopenia)
Antibody mediated immunity
Cell mediated immunity (including AIDS)
Staphylococcus aureus and Streptococcus pneumoniae
Streptococcus pneumonia and viral infections
Tuberculosis, Legionella and AIDS-related infections
