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Infection And Immunity > Introduction to Infection and Microbes > Flashcards

Introduction to Infection and Microbes Flashcards

1
Q

Define infection

A

An invasion of a host’s tissues by microorganisms causing a disease (pathological change/damage)

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2
Q

What causes the disease in an infection?

A

Microbial multiplication
Toxins
Host response

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3
Q

Define zoonoses

A

Infectious diseases of animals that can naturally be transmitted to humans

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4
Q

What are the 3 ways of horizontal transmission?

A

Contact (direct, indirect, vectors)
Inhalation (droplets, aerosols)
Ingestion (faecal-oral)

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5
Q

What is vertical transmission?

A

Transmission of an infection from mother to child before or after birth (eg. HIV)

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6
Q

Give some examples of types of exotoxins

A

Cytolytic
AB toxins
Super antigens
Enzymes

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7
Q

What are the 4 types of microbe?

A

Viruses
Bacteria
Parasites
Fungi

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8
Q

What is the key characteristic of all microbes?

A

They multiply

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9
Q

What is a viral envelope made of?

A

Lipopolysaccharides and lipids

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10
Q

What is the difference between gram positive and gram negative bacteria?

A

Gram positive bacteria have a very thick peptidoglycan wall whereas gram negative have a thinner peptidoglycan wall and 2 membranes. Gram positive bacteria hold the gram stain.

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11
Q

What are obligate anaerobes?

A

Microbes that require oxygen free environments to survive

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12
Q

How do we name bacteria?

A

Linnaean taxonomy

Genus then species eg. Staphylococcus aureus

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13
Q

Give an example of gram positive cocci

A

Staphylococcus aureus
Streptococcus pneumoniae
Enterococcus faecalis

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14
Q

Give an example of gram negative cocci

A

Neisseria meningitidis

Mortadella catarrhalis

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15
Q

Give an example of gram positive bacilli

A

Listeria monocytogenes

Bacillus cereus

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16
Q

Give an example of gram negative bacilli

A 
Escherichia coli (E-coli) 
Klebsiella pneumoniae
Salmonella typhi 
Pseudomonas aeruginosa
Haemophilus influenzae
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17
Q

Name a yeast

A 
Candida albicans (thrush) 
Cryptococcus neoformans (meningitis)
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18
Q

Name a mould (fungi)

A

Aspergillus species (lung infection)

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19
Q

Name a protozoa (single celled) parasite

A

Giardia lamblia

Plasmodium falciparum

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20
Q

Name a helminth (worm, multicellular)

A

Roundworms
Tapeworms
Flukes

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21
Q

What are the beneficial effects of normal flora?

A

Sheer number in bowel make it hard for invading pathogen to compete for nutrients and site
Some produce antimicrobials
Helps develop the immune system
Can provide nutrients (vitamin K)
Can aid in digestion and absorption of nutrients

22
Q

What are mycoplasma?

A

Small, prokaryotic organisms with no peptidoglycan in their cell walls
Have a single plasma membrane
Extremely small so frequently pass through filters

23
Q

Describe chlamydiae

A

Small bacteria that are obligate intracellular parasites
Grow in cytoplasmic vacuoles
Have 2 lipid bilayers

24
Q

Describe rickettsia

A

Small, rod-like or coccobacillary shaped
Double layered, gram negative cell wall
Transmitted by arthropods (eg. Fleas)

25
Q

What does positive RNA mean?

A

Directly encodes for mRNA

26
Q

What does negative RNA mean?

A

Does not directly encode for mRNA

27
Q

Why is HPV linked to cervical cancer?

A

Direct carcinogen as it express E6 and E7 proteins that inhibit p53 and pRB protein function (important for cell proliferation)

28
Q

What is the normal range for CRP?

A

< 5

29
Q

What bacteria causes cellulitis?

A

Staph aureus

Strep pyogenes

30
Q

Briefly describe strep pyogenes

A

Gram positive
Group A streptococcus
Beta haemolytic (complete destruction of RBCs on blood agar)

31
Q

What is the sweep test?

A

Performed when looking for necrotising fasciitis

If the fascia is dead then there will be no resistant to sweeping the finger around in a small surgical incision

32
Q

What is the treatment for necrotising fasciitis?

A

Supportive care - IV fluids, analgesia, antypyretics
Antibiotics
ITU referral - high mortality condition
Surgery - drain pus, remove infected source, amputation

33
Q

Why can’t necrotic tissue recover?

A

Lack of blood supply

34
Q

What do we think about when choosing an Abx?

A

Severity of infection
Site of infection
Likely pathogen(s)
Route of administration
Possible adverse effects - allergy, interactions with other drugs, renal/hepatic impairment
Ecological impact - don’t select for other organisms

35
Q

What is the likely bacterial cause of NF?

A

Strep pyogenes

Group A beta haemolytic

36
Q

Describe alpha haemolysis and bacteria that do it

A

Produces a green appearance on agar
Strep viridans group
Strep pneumoniae

37
Q

Describe the virulence factors of strep pyogenes

A 
M proteins - antiphagocytic
Exotoxins - streptolysin for cell lysis 
Streptokinase - lysis of clots
Streptodornase - DNAases to promote spread
C5a peptidase - inactivate complement
38
Q

Which Abx are active against streptococci?

A 
Beta lactams (penicillins, cephalosporins, carbapenems)
Glycopeptides (vancomycin)
39
Q

What is toxin-mediated disease treatment?

A

Anti-toxin therapy - high dose immunoglobulin

Interfere with toxin production - Abx that inhibit protein synthesis

40
Q

What is the empiric treatment for strep infections?

A

Tazocin and clindamycin

41
Q

If group A strep is identified, which Abx do we use?

A

Benzylpenicillin and clindamycin

42
Q

Name some group A strep diseases (other than cellulitis and NF)

A 
Acute pharyngitis/tonsillitis 
Scarlet fever
Impetigo 
Erysipelas 
Puerperal sepsis ('childbed fever')
43
Q

What are some consequences post-strep infections?

A

Acute rheumatic fever - cross reaction between heart/joint tissue and strep antigens - valve damage/pericarditis/endocarditis etc
Acute glomerulonephritis - antigen-antibody complexes on basement membrane

44
Q

Which bacteria falls under non-haemolytic ‘strep’?

A

Enterococcus faecalis

45
Q

Name some common staph skin infections

A

Impetigo
Furuncle (boil) - hair follicles
Surgical wound infection

46
Q

Is staph aureus coagulase positive or negative?

A

Positive

47
Q

What colours do coagulase positive and negative tests produce?

A 
Positive = gold
Negative = white
48
Q

Describe some features of coagulase negative bacteria

A

Low violence
Generally don’t cause infections in otherwise healthy people
Can create biofilms

49
Q

Which of staph and strep is typically localised and which is spreading?

A 
Staph = localised
Strep = spreading
50
Q

What Abx do we use for staph?

A

Flucloxacillin
Beta lactam combinations eg. Coamoxiclav and tazocin
Vancomycin for flucloxacillin resistant strains

51
Q

Why is flucloxacillin generally a good choice?

A

Resistant to staph beta lactamase

Infection And Immunity (9 decks)

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