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Flashcards in Microbiology study guide Deck (21):
1

Describe Prokaryotes

Small, self replicating single celled microorganisms

2

Describe eukaryotes

Single celled fungi causing conditions such as thrush

3

Describe viruses

Small acellular agents consisting of genetic material contained within a protein coat

4

Describe prions

Infectious protein particles that can alter the shape and behaviour of a host protein

5

What is the cycle of infection

1. Infectious agent 

(Prokaryote, eukaryote, virus, prion)

2. Resevoir 

(atmosphere, skin, food)

3. Portal of exit

(cough, gut, GI)

4. Mode of transmission

(direct, indirect)

5. Portal of entry

(inhalation, ingestion, injection)

6. Susceptible host

(immunocompromised)

6

Describe methicillin resistant staphylococcus aureus?

Cause disease with the carriage of proteins that allow it to survive in the presence of more than one antibiotic.

In the nose, mouth and GI tract of healthy individuals

Gram positive cocci, divide in alternate plains to form clumps

 

Coagulate plasma

 

Falcutative anaerobe

7

Describe vancomycin resistant enterococcus faecalis?

High numbers in the GI tract, isolatef from mouth

 

UTI infections via catheterizaiton, trauma or disease 

 

Gram positive cocci in chains

 

Grow in presence of bile 

Lancefield group D antigen 

Falcultative anaerobe

8

Describe C. diff

Associated with environment and soil

Obligate anaerobes, sensitive to oxygen

Form Spores

Produced in response to stress

Gram positive bacilli 

Produce exoproteins and toxins

9

Describe HBV

Hepatitis b virus consists of a small double stranded DNA genome encased within a protein caspid (HBc Antigens) and glycoprotein envelope (HBs antigen)

 

Identified by detection of antigen in serum samples, particularly HBs and HBe

10

Describe RSV

largely enveloped virus (covered in a lipid bilayer) with a single stranded RNA genome

RT-PCR and detection of viral antigens in immunoassays are used for identification

11

What is resistance based upon?

genetic variation, natural selection & horizontal gene transfer. 

12

What is a biofilm?

 

Organism behaving as part of multi-cellular community.

•  3 dimensional structure

•  Contains interfaces

•  Spatial heterogeneity

•  Permeated by water channels

•  Organisms resistant to antimicrobial agents & host defenses. 

13

What is a persistor cell?

Give tolerance not resistance

  • Metabolically inert
    • very slow growth
    • Dormant or non-dividing
  • Sub population of cells
    • transient state
    • Planktonic & biofilm populations
    • Enriched in biofilms 

14

Name two common resistance mechanisms?

B-lactamases

enzymes produced by bacteria that provide multiple resistance to B-lactam antibiotics- break the B-lactam ring

PBP2

Responsible for the resistance seen in MRSA

15

What would constitite an ideal antibiotic?

 

  • selective toxicity/minimal toxicity to host
  • cidal
  • long half lide
  • appropriate tissue distribution
  • no adverse drug interactions/side effects
  • oral & parenteral preparations

16

How do gram negative orgamisms cause shock?

Antigen or endotoxin interact with macrophages

Macrophages release cytokines into blood

Cytokines travel to anterior hypothalamus

Prostaglandin E is released which increases the body's set thermal point

Body starts to think its cold and shivers

Causes fever= increased survival 

17

Describe Sepsis

  • Small blood vessels become “leaky” and lose fluid into the tissues
  • Lower blood volume requires heart to work harder to maintain oxygenation of tissues (↑HR)
  • Poor tissue oxygen perfusion mean blood supply to less essential organs (skin, kidneys, liver is shut down to try to maintain blood supply to brain
  • Blood clotting system is activated causing blood clotting in tiny blood vessels→ uses up all clotting factors→ increased risk of haemorrhage 

18

Describe the cell wall of gram positives

Thick multi-layer PG

•  Target of Penicillin 

19

Describe the cell wall of gram negatives

Outer membrane

– Periplasm
– Thinner PG layer

•  Target of Penicillin 

20

Describe lipopolysaccharide?

Gm-ve
– Outer membrane asymmetric

– Surface nearly all LPS

• Glycolipid

– lipid A
– core polysaccharide

– O-chain/antigen

Structural role
Antigen & Bacterial Toxin 

21

What is the difference between flagella and fimbriae?

Gm +ve Fimbriae
– non-flagella protein appendages

Gm -ve Pilus
– no motor, Pilin repeated protein unit