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Infection > Week 1 > Flashcards

Week 1 Flashcards

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?

A

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

21
Q

What does slime allow?

A

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

22
Q

What are spores?

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?

A

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

24
Q

What can plasmids code for?

A

Antimicrobials resistance

Pathogenicity factors

25
Q

What characteristics are used to help to classify bacteria?

A 
Gram reaction
Cell shape
Endospore (presence, shape, position)
Atmospheric preference 
Fastidiousness
Key enzymes
Serological reactions 
DNA sequences
26
Q

What are the major groups of Gram positive bacteria?

A

Staphylococci (catalase positive)
Streptococci (catalase negative)
Gram positive bacilli - further divided into sporing and non-sporing

27
Q

What are the major groups of gram negative bacteria?

A

Gram negative cocci, coccobacilli, bacilli

28
Q

What are obligate pathogens?

A

Always associated with disease

Eg HIV

29
Q

What are conditional pathogens?

A

Cause disease if certain conditions are met

30
Q

Give some examples of double stranded DNA viruses

A 
Poxvirus
Herpesvirus
Adenoviruses
Popovaviruses
Polyomaviruses
31
Q

With regard to its DNA, what type of virus is hepatitis B?

A

Double stranded with single stranded portions

32
Q

Give some single stranded DNA viruses

A

Parvoviruses

33
Q

How do DNA viruses usually replicate?

A

In the nucleus of host cells
Produce a polymerase which reproduces viral DNA.
Not normally incorporated into host’s chromosomal DNA

34
Q

How is RNA sense (+ss) viruses reproduced?

A

May serve directly as mRNA

It is translated into structural protein and an RNA-dependent RNA polymerase

35
Q

How do RNA antisense (-ss) replicate?

A

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
Q

Which virus has ss+ RNA that cannot act as mRNA? What happens instead?

A

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
Q

What are capsids?

A

Protein coat made up of repeating units

Have icosahedral or helical symmetry

38
Q

Describe icosahedral symmetry and helical symmetry

A

Icosahedral - capsids form an almost spherical structure

Helical - found in RNA viruses that have capsids bound around the helical nucleic acid

39
Q

List some enveloped DNA viruses

A

Hepatitis B
Herpes
(Smallpox)

40
Q

List some DNA non-enveloped viruses

A

Human papilloma virus

41
Q

Name some RNA enveloped viruses

A 
HIV
Rubella
Rotavirus
Coronavirus 
Influenza
42
Q

List some RNA non-enveloped viruses

A

Polio

Hep A

43
Q

What is enveloped in enveloped viruses?

A

Nucleic acid and capsid proteins

44
Q

Where does the envelope come from in enveloped viruses?

A

A lipid envelope derived from the membrane

45
Q

What antibiotic would you give to treat streptococcus pneumoniae?

A

Amoxicillin

46
Q

What antibiotic would you use to rear pseudomonas aeruginosa in pneumonia?

A

Ciprofloxacin

47
Q

What is different about Staph aureus that distinguishes it from other species of staphylococcus?
What is significant about it?

A

It is coagulase positive

Catalyses conversion of fibrinogen to fibrin and may help the organism to form a protective barricade

48
Q

What is the most common/important of coagulase negative staphylococci?

A

Staphylococcus epidermis

49
Q

What are the two categories that Streptococci can be divided into?

A

Type of haemolysis
α haemolytic - incomplete
β-haemolytic - complete

Infection (14 decks)

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