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1. Principles > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What does Gram Positive stain?

A

Purple

  • thick peptidoglycan layer
  • single phospholipid layer
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2
Q

What does Gram Negative stain?

A

piNk

  • thin peptidoglycan layer
  • two phospholipid bilayers
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3
Q

What is a pathogen?

A

harmful organism

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4
Q

What is a commensal?

A

organism that is part of the normal flora

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5
Q

What is an opportunistic pathogen?

A

normally only causes infection in immunocompromised individuals

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6
Q

How do bacteria grow?

A

replication through binary fission

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7
Q

What are the 3 enviroments that bacteria could grow in?

A

Aerobic - presence of oxygen (air)
Microaerophilic - reduced O2 conc and enriched CO2
Anaerobic - No o2 present

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8
Q

What is an exotoxin?

A

Usually gram positive bacteria

Produced inside cell and exported from it

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9
Q

What is an endotoxin?

A

Usually gram negative bacteria

Part of gram negative bacterial cell wall

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10
Q

Descirbe Streptococcus?

A

Gram +ve
Aerobic
Cocci chains
Alpha haemolysis (partial) – Strep pneumoniae (pneumonia, meningitis), Strep viridans (endocarditis)
Beta haemolysis (complete) – Group A Strep (throat, skin infection), Group B strep (neonatal meningitis)

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11
Q

Describe Enterococcus?

A 
Gram +ve
Aerobic 
Cocci chains 
Non-haemolytic 
Normal gut commensal and cause of UTIs
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12
Q

Describe Staphylcoccus?

A

Gram +ve
Cocci clusters
Coagulase positive (golden) – Staph aureus – wound, skin infections
- Flucloxacillin antibiotic of choice
- Common cause of bacteraemia
Coagulase negative (white) – Staph epidermidis – normal skin commensal, IV line infections

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13
Q

Describe the mechanism of fever?

A
  • Antigen attacks macrophage
  • Releases cytokines
  • Travel to anterior hypothalamus of the brain
  • Stimulates production of prostaglandin E
  • Resets body’s thermal set point
  • Body perceives it is cold, shivers to conserve heat
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14
Q

What is the coagulase test?

A

Test to distinguish staphylococcus aureus from other staphylococcus
Positive = staph. a

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15
Q

What is haemolysis?

A

Test to distinguish streptococci

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16
Q

Name some gut commensals?

A

E.coli
Klebsiella
Proteus

17
Q

Name some gut pathogens?

A

Salmonella
Shigella
E.coli O517

18
Q

Name gram negative bacilli?

A

Coliforms

i.e. gut commensals and gut pathogens

19
Q

Name some strict anaerobes?

A

Gram negative bacilli
Pseudomonas aeruginosa
Legionella pneumophilia

20
Q

What is Haemophilus influenzae?

A

Small gram negative bacillus

Common cause of chest infection, especially in COPD exacerbations

21
Q

What are the 3 types of bacterial gene transfer?

A

Transformation
DNA from dead bacteria taken up by living bacteria and incorporated in plasmids or the bacterial chromosome
Conjugation
Sex pilus (fimbria) formed by one bacteria through which plasmid DNA can be transferred
Transduction
Viruses infecting bacteria can transfer bits of DNA from one bacterium to another

22
Q

5 Is of Infection?

A 
Inhalation
Ingestion
Inoculation
mother to Infant
Intercourse
23
Q

What are bactericidal antibiotics?

A

Kill bacteria

24
Q

What are bacteriostatic antibiotics?

A

inhibit cell growth

25
Q

What 3 classes of antibiotics work on the cell wall?

A

Penicillin
Cephalosporins
Glycopeptides

26
Q

Name some penicillins and their mechanism of action?

A

Flucloxacillin, Co-Amoxiclav, Amoxicillin

Inhibit cell wall synthesis by preventing cross-linking of peptidoglycan subunits

  • Bactericidal
  • Beta-lactam antibiotic
  • Excreted (rapidly) via kidneys
  • type 1 hypersensitivity
27
Q

Describe Cephalosporins and name an example?

A

Ceftriaxone

Inhibit cell wall synthesis
Bactericidal
Beta-lactam antibiotic
Excreted by kidneys

May induce Clostridium difficile infection so their use is limited in hospital

28
Q

Give an example of Glycopeptides and their mechanism of action?

A

Vancomycin

Binds to end of growing chain, prevents cross-linking and weakens bacterial cell wall
Bactericidal
Only active against organisms with gram positive cell walls
Excreted in urine

29
Q

Name the 3 types of antibiotics that inhibit protein synthesis?

A

Macrolides
Tetracyclines
Aminoglycosides

30
Q

Describe and name some macrolides?

A

Erythromycin, clarithromycin, azithromycin

Attaches to bacterial ribosomes
bacteriostatic i.e. protein synthesis can resume when antibiotic is removed
excreted via biliary tract

31
Q

Describe and name some tetracyclines?

A

Doxycycline

Broad spectrum, can destruct intestinal flora (so increased secondary infections)
bacteriostatic i.e. protein synthesis can resume when antibiotic is removed
excreted via biliary tract

32
Q

Describe and name some aminoglycosides?

A

Gentamicin

Inhibit protein synthesis but are bactericidal
Mainly active against gram negative aerobic organisms

Toxicity – kidney damage and damage of CN VIII – vestibulocochlear (deafness and dizziness)
Excreted in the urine

33
Q

Name 3 antibiotics that act on bacterial DNA?

A

Metronidazole
Trimethoprim
Fluoroquinolones

34
Q

Describe Metronidazole?

A

Causes strand breakage of bacterial DNA
Treat true anaerobic infections
Interacts with alcoho

35
Q

Describe Trimethoprim?

A

Inhibits bacterial folic acid synthesis

Some activity against some gram negative and some gram positive

36
Q

Describe Fluoroquinolones?

A

Ciprofloxacin, Levofloxacin

Prevent supercoiling of bacterial DNA 
Bactericidal 
Restricted use in order to prevent Clostridium difficile 
Weakens tendons, causes seizures
Excreted in urine
37
Q

Describe Virus reproduction?

A

Attachment
Interact with specific receptors in target cell, ligand > receptor
Entry
Endocytosis (non-enveloped viruses)
Uncoating
Viral nucleic acid released from capsid
Nucleic acid and protein synthesis
Host ribosomes used, host polymerases may be used also
Assembly
Nucleic acid and proteins packaged together
Release
Budding - Virus released with envelope derived from host cell membrane and doesn’t kill cell
Lysis - Viruses accumulate until cell bursts and kills cell

1. Principles (9 decks)

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