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S and P- POI > Microbiological virulence factors > Flashcards

Microbiological virulence factors Flashcards

1
Q

What are the classical characteristics of viruses?

A

Obligate intracellular parasites
Smaller, DNA or RNA
Metabolically inert
Use host cell synthetic machinery

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2
Q

What are the classical characteristics of bacteria?

A

Unicellular
Prokaryotic- nucleus not organised, double stranded circular DNA in cytoplasm
Rigid peptidoglycan cell wall
Binary fission

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3
Q

What are the classical features of fungi?

A

Eukaryotic
Rigid cell wall
Sexual and asexual replication
Unicellular yeast like or filamentous conidia/spore bearing forms

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4
Q

What are the classical features of parasites?

A

Eukaryotic
Unicellular protozoa or multicellular helminths
Many with intermediate hosts in complex life cycle

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5
Q

What is the cytoplasmic membrane of bacteria made of?

A

Proteins and phospholipids

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6
Q

What does the cytoplasmic membrane of bacteria not contain?

A

Sterols (only found in eukaryotes)

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7
Q

What is the function of the bacterial cell membrane?

A

Synthesise and export cell wall components
Respiration
Secretion of extracellular enzymes and toxins
Uptake of nutrients by active transport mechanisms

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8
Q

What is the function of bacterial cell wall?

A

Protective- rigid so can withstand osmotic and mechanical stress + provides barrier against certain toxic chemical and biological agents
Gives shape to the bacterium
Firm base for pili, fimbriae and flagella
Contains antigens- important in virulence and in host antibody production

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9
Q

What are the 2 different types of bacterial cell wall?

A

Gram positive

Gram negative

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10
Q

What are gram positive cell walls like?

A

2 layers
Peptidoglycan and teichoic acids
Inner plasma membrane and outer thick peptidoglycan layer

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11
Q

What are Gram negative cell walls like?

A

3 layers
Thin peptidoglycan layer
Outer plasma membrane containing lipopolysaccharide (LPS) and outer membrane proteins (OMP)

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12
Q

What is the bacterial capsule?

A

Mucoid polysaccharide layer

Consists of polymerised d-glutamic acid

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13
Q

What is the function of the bacterial capsule?

A

Anti-phagocytic activity anf prevents attack by complement

Adhesion

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14
Q

What is the capsule used for?

A

Laboratory diagnostic tests and used in vaccines

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15
Q

What are 2 of the main types of pili and what do they do?

A

Sex pili- transfer DNA by conjugation

Common pili- for attachment

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16
Q

What is the function of pili?

A

They are important in adhesion and anti-phagocytic activity

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17
Q

What is the function of flagella?

A

Motility

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18
Q

Give example of intracellular structures in bacteria?

A

Nucleoid
Ribosomes
Inclusion granules
Endospores

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19
Q

What are the basic requirements for bacteria in terms of nutrition?

A

Basic requirements- carbon, nitrogen, water and a source of energy

20
Q

How is the fact that some bacteria require specific gases and growth factors used diagnostically?

A

Media can be developed for selective isolation and identification of particular bacteria

21
Q

What are the classifying features of bacteria?

A 
Shape- round, long, curved, pairs, clusters, chains etc
Atmospheric requirement- requires oxygen, increased co2 and oxygen toxic
Spore production (dangerous feature)
22
Q

What are the main bacteria identification tests?

A 
Enzyme production- Testing to see whether they produce certain enzymes such as:
Urease
Catalase
Coagulase
Oxidase

Toxin production:
Protein synthesis inhibitors
Haemolysins
Superantigens

23
Q

What are the components of the Gram stain?

A

Stain 1= Methyl violet and lugol’s iodine (violet-blue)

Stain 2= Methyl red (pale pink-red)

24
Q

What component of the Gram stain does both Gram positive and Gram negative bacteria take?

A

Gram positive- Stain 1 (violet blue)

Gram negative- Stain 2 (pale pink red)

25
Q

How are Gram positive first classified?

A

Based on shape- rods or cocci

26
Q

What are Gram positive bacteria differentiated based on after their shape?

A

How they aggregate and other biochemical test results

27
Q

How do staphylococcus aggregate and how do they respond to catalase test?

A 
In clusters (grapes)
Catalase positive
28
Q

How do streptococcus aggregate and how do they respond to catalase test?

A

In pairs/chains

Catalse negative

29
Q

How are staphylococci differentiated?

A

Based on coagulase test
Positive- s.aureus
Negative- s.epidermidis and s.saprophyticus and others

30
Q

What are streptococci differentiated based on?

A

Extent of haemolysis that they cause:
Alpha haemolytic- (must be further differentiated using optochin- toxic chemical)
Optochin sensitive- s.pneumoniae
Optochin resistant- viridans group

Beta haemolytic-
Group A- s. pyogenes
Group B- s.agalactiae
Group D- enterococci

Non-haemolytic
Streptococcus milleri
Anaerobic streptococci

31
Q

What types of infection are caused by staphylococci?

A

Staphylococcus aureus- severe infection e.g. skin/soft tissue, endocarditis and osteomyelitis
Coagulase negative staphylococci- Skin commensals of low pathogenic potential and can infect prosthetic material causing line, pacemaker infections and endocarditis

32
Q

What type of infection do group B strep tend to be associated with?

A

Neonatal infection because 1/3 of healthy women carry B strep in genital tracts and can be transferred to baby during delivery

33
Q

What are the two groups of spore forming bacteria?

A

Bacillus sp.- bacillus cereus and bacillus anthracis

Clostridia sp.- clostridium perfringens, clostridium tetani, clostridium botulinum and clostridium difficile

34
Q

What do endospores contain?

A

Bacterial DNA, cytoplasm, plasma membrane, peptidoglycan, little water, dipicolinic acid and keratin like coat

35
Q

When are endospores formed?

A

In response to adverse environmental conditions

36
Q

What are endospores resistant to?

A

Chemical inactivation

37
Q

What is the function of endospores?

A

Protective- Survive drying, heat, dehydration and radiation

38
Q

What is anthrax used as?

A

Chemical weapon

39
Q

How is anthrax treated?

A

Ciprofloxacin

40
Q

What is Hide Porter’s disease?

A

Cutaneous anthrax carried in contaminated animal hides, an occupational disease
Characterised by black eschars, oedema and swelling

41
Q

What does the periplasm of gram-negative bacteria contain?

A

Enzymes with hydrolytic function
Enzymes that inactivate antibiotics
Oligosaccharides

42
Q

What is haemophillus influenzae?

A

Gram negative cocco bacilli found in the nasal cavity that doesn’t cause much of a problem as most people are vaccinated

43
Q

What does Gram negative outermembrane contain?

A 
Phospholipids
Lipopolysaccharide (LPS)
44
Q

What is important about lipopolysaccharide?

A

It is toxic to humans and can cause fever and shock (endotoxin shock)

45
Q

What does LPS consist of?

A 
Lipid A (toxic component of endotoxin)
Core polysaccharide
O antigen (major surface antigen of Gram-negative cells)
46
Q

How are a lot of gram negative bacteria differentiated?

A 
Using another test- oxidase
Oxidase negative-
Coliforms e.g. E.coli, Klebsiella spp, Enterobacter spp, Seratia spp. Proteus spp.
Oxidase positive-
Pseudomonas spp.

S and P- POI (7 decks)

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