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Week 1 Flashcards

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0
Q

What are commensals/microbiota

A

Normal bacteria that don’t cause any harm

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1
Q

What is an infection?

A

Invasion and multiplication of microorganisms which are not normally present within the body

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2
Q

When can commensals be harmful?

A

If they get into wrong places in the body

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3
Q

What are the modes of transmission of an infection?

A

Horizontal transmission
Inhalation
Ingestion
Vertical transmission

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4
Q

How do microorganisms cause disease?

A 
Exposure
Adherence
Invasion
Multiplication
Dissemination
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5
Q

What is virulence?

A

The degree of pathogenicity within a group of parasites as indicated by fatality rates and/or ability of the organism to invade host’s tissues
Ability to cause serious disease

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6
Q

What is pathogenicity

A

Ability to cause disease. Determined by virulence factors

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7
Q

Give some virulence factors

A

Exotoxins

Endotoxins

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8
Q

What do endotoxins do?

A

Stimulate macrophages to produce interleukin-1 (IL-1) and tumour necrosis factor (TNF)

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9
Q

What do exotoxins do?

A

Cause local or distant damage.

  • cause non-specific activation of T cells causing inflammatory cytokine production
  • interfere with host cell protein synthesis
  • interfere with neurological or neuromuscular signalling
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10
Q

How does cholera cause diarrhoea (briefly)

A

Secretes exotoxin
B subunit binds to the epithelial cell
A activates adenylyl cyclase causing Na and Cl efflux from the cell.

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11
Q

What are the disease determinants?

A

Pathogen
Patients
Practice
Place

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12
Q

What factors affect the pathogen as a disease determinant?

A

Virulence factors
Inoculum size
Antimicrobial resistance

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13
Q

Examples of some supportive investigations

A 
FBC
CRP
Liver and renal function 
Imaging - X-ray, MRI, ultrasound
Histopathology
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14
Q

What factors affect the patient as a disease determinant?

A

Site of infection

Co-morbidities

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15
Q

Structure of a Gram positive cell wall?

A

Thick peptidoglycan layer and a cell membrane

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16
Q

Structure of a Gram negative cell wall?

A

Three layers

  • inner and outer membrane
  • thin peptidoglycan layer
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17
Q

Function of bacterial cell wall?

A

Maintains shape and protects cell from differences in osmotic tension between the cell and the environment

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18
Q

Structure and function of the capsule?

A

Loose polysaccharide structure

Protects the cell from phagocytosis and desiccation

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19
Q

What does the lipopolysaccharide do?

A

Protects Gram negative bacteria from complement mediated lysis. A potent stimulator of cytokine release.

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20
Q

What allows E. coli to bind to ureteric epithelial cells?

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A

Specialised fimbriae (P fimbriae) that bind to mannose receptors on the cells

21
Q

What does slime allow?

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A

Polysaccharide material secreted by some bacteria growing in biofilms.
Protect the organism from immune attack and antibiotics

22
Q

What are spores?

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A

Metabolically inert form triggered by adverse environmental conditions. Adapted for long-term survival. Allow re growth under suitable conditions

23
Q

How is DNA stored in prokaryotes?

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A

Packed into a chromosome.
DNA is coiled and then supercoiled - DNA gyrase
Accessory DNA in plasmids

24
What can plasmids code for?
Antimicrobials resistance | Pathogenicity factors
25
What characteristics are used to help to classify bacteria?
``` Gram reaction Cell shape Endospore (presence, shape, position) Atmospheric preference Fastidiousness Key enzymes Serological reactions DNA sequences ```
26
What are the major groups of Gram positive bacteria?
Staphylococci (catalase positive) Streptococci (catalase negative) Gram positive bacilli - further divided into sporing and non-sporing
27
What are the major groups of gram negative bacteria?
Gram negative cocci, coccobacilli, bacilli
28
What are obligate pathogens?
Always associated with disease | Eg HIV
29
What are conditional pathogens?
Cause disease if certain conditions are met
30
Give some examples of double stranded DNA viruses
``` Poxvirus Herpesvirus Adenoviruses Popovaviruses Polyomaviruses ```
31
With regard to its DNA, what type of virus is hepatitis B?
Double stranded with single stranded portions
32
Give some single stranded DNA viruses
Parvoviruses
33
How do DNA viruses usually replicate?
In the nucleus of host cells Produce a polymerase which reproduces viral DNA. Not normally incorporated into host's chromosomal DNA
34
How is RNA sense (+ss) viruses reproduced?
May serve directly as mRNA | It is translated into structural protein and an RNA-dependent RNA polymerase
35
How do RNA antisense (-ss) replicate?
Contains an RNA-dependent RNA polymerase that transcribes the viral genome into mRNA. Or, the transcribed RNA can act as a template for further viral (antisense) RNA.
36
Which virus has ss+ RNA that cannot act as mRNA? What happens instead?
Retroviruses Transcribed into DNA by reverse transcriptase and incorporated into host DNA. Subsequent transcription to make mRNA and viral genomic RNA is under control of host transcriptase enzymes.
37
What are capsids?
Protein coat made up of repeating units | Have icosahedral or helical symmetry
38
Describe icosahedral symmetry and helical symmetry
Icosahedral - capsids form an almost spherical structure | Helical - found in RNA viruses that have capsids bound around the helical nucleic acid
39
List some enveloped DNA viruses
Hepatitis B Herpes (Smallpox)
40
List some DNA non-enveloped viruses
Human papilloma virus
41
Name some RNA enveloped viruses
``` HIV Rubella Rotavirus Coronavirus Influenza ```
42
List some RNA non-enveloped viruses
Polio | Hep A
43
What is enveloped in enveloped viruses?
Nucleic acid and capsid proteins
44
Where does the envelope come from in enveloped viruses?
A lipid envelope derived from the membrane
45
What antibiotic would you give to treat streptococcus pneumoniae?
Amoxicillin
46
What antibiotic would you use to rear pseudomonas aeruginosa in pneumonia?
Ciprofloxacin
47
What is different about Staph aureus that distinguishes it from other species of staphylococcus? What is significant about it?
It is coagulase positive | Catalyses conversion of fibrinogen to fibrin and may help the organism to form a protective barricade
48
What is the most common/important of coagulase negative staphylococci?
Staphylococcus epidermis
49
What are the two categories that Streptococci can be divided into?
Type of haemolysis α haemolytic - incomplete β-haemolytic - complete

Infection (14 decks)

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