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ESA3 > Infection And Immunity > Flashcards

Infection And Immunity Flashcards

1
Q

What is an infection?

A

An invasion of host tissues by micro-organisms

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2
Q

3 mechanisms pathogen cause disease

A

Microbe multiplication
Toxins
Host response

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3
Q

4 environmental sources for pathogen transfer

A

Food, air, water, surfaces

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4
Q

Microbiota?

A

Commensal, microbes normally carried by host on skin and mucosal surfaces.
Normally harmless
May cause harm if transfer or immunocompromised

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5
Q

How is legionella transferred?

A

Water droplets

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6
Q

Modes of horizontal pathogen transfer

A

Contact - direct, indirect, vector
Inhalation - droplets, aerosols
Ingestion - contaminated water, food, f-o

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7
Q

Vertical pathogen transfer

A

Mother to child, at or before birth

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8
Q

What do pathogens do once in ?

A

Exposure, adherence, invasion, multiplication, disemmination

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9
Q

Virulence factors

A

Exotoxins - superantigens, AB toxins, enzymes, cytolytic

Endotoxins - LPS

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10
Q

What factors determine severity of pt disease after exposure to a pathogen?

A

Pathogen - virulence, inoculum size, Ab resistance

Pt - site of infection, co-morbidities

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11
Q

E.g. UTI by commensal

A

E. coli

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12
Q

E.g Community acquired pneumonia

A

Streptococcus pneumoniae

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13
Q

Eukaryotes have 80s ribosome, what about prokaryotes?

A

70s

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14
Q

E.g. Gram neg, diplococcus

A

N. meningitidis

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15
Q

Grape like cluster of coccus?

A

Staph aureus

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16
Q

Difference in structure b/w gram positive and negative bacteria?

A

Positive- thick peptidoglycan wall with teichoic acid retains crystal violet stain

Negative - Thin peptidoglycan layer with no teichoic acid, outer layers of lipoprotein and lipopolysaccharide also present. This allows crystal violet colour to be washed out, and counterstain (safranin) is visible.

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17
Q

Example of unicellular fungi

A

Candida albicans

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18
Q

Example of multicellular fungi

A

Aspergillus, dermatophytes

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19
Q

What is a protozoa?

A

A single celled eukaryotic parasite

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20
Q

What mechanism of action - beta lactams?

A

Inhibit cell wall synthesis - binds to penicillin-binding protein, which is important in forming cross-links between chains in cell wall. Without these links, cell wall weak - unviable

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21
Q

What mechanism of action - glycopeptides?

A

Inhibits cell wall synthesis, sits on chains to be cross linked in cell wall- prevents PBP making the links. Unviable cell wall (too weak)

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22
Q

Example of glycopeptide?

A

Vancomycin

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23
Q

Example of beta-lactam?

A

Penicillin

Amoxicillin

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24
Q

Why can’t we use vancomycin to treat bacterial meningitis?

A

Often caused by Neisseria meningitidis, which is gram negative - vancomycin is too big to be taken up past the cell walls of gram negative bacteria

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25
Q

Two antibiotics that affect bacterial protein synthesis?

A

Tetracycline and doxycycline - NOT FOR KIDS

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26
Q

Pt has gram negative sepsis. You need to give a protein synthesis inhibitor - which one and what are the potential side effects?

A

Aminoglycosides - gentamycin

Potentially nephrotoxin
TDM (therapeutic dose monitoring required)

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27
Q

Erythromycin and clarithromycin are types of?

A

Macrolides, inhibitors of protein synthesis

28
Q

Ciprofloxacin works by inhibiting nucleic acid synthesis. How?

A

Inhibits DNA gyrase and topoisomerase
V active against gram neg
C. dif association

29
Q

Give one mechanism by which bacteria can be rsistant to penicillin

A

They may have a beta-lactamase enzyme that will inactivate the drug

30
Q

What can be done to deal with a strain of bacteria that have beta lactamase activity?

A

Combine a beta lactam with a beta lactamase inhibitor. E.g. Co-amoxiclav

31
Q

You suspect that a pt has an infection. What supportive investigations can you do?

A 
Full blood count - neutrophils, lymphocytes
CRP
LFTs, KFTs
Imaging - xray, ultrasound, MRI
Histopathology
32
Q

How would you check if a pt had a virus?

A

Virology

Antigen detection
Antibody detection
Nucleic Acid detection - DNA/RNA

33
Q

Virus basic structure

A

Nucleic acid, protein coat

+/- LPS/lipid capsule, spikes

34
Q

What is the baltimore classification of viruses?

A

Classes based on nucleic acid structure- i.e. dsDNA, ssDNA, ssRNA etc.

35
Q

Example of dsDNA non-enveloped viruses

A

Adenovirus,

Human papilloma virus

36
Q

DsDNA enveloped virus

A

Herpes virus
Hep B
Molluscum contagiosum

37
Q

Example of RNA virus

A

Hep A, E
Influenza
Norovirus

38
Q

Bacteria basic structure

A

Circular DNA,
Plasma membrane
Cell wall
Ribosome

+/- envelope, pili, flagellum, plasmid

39
Q

2 example of gram positive bacilli

A

Listeria monocytogenes
Bacillus anthracis
Bacillus cereus

40
Q

Examples of gram neg bacilli

A

Salmonella typhi
Escherichia coli
Haemophilus influenzae

41
Q

Some bacteria have enzymes that increase their virulence, give an example

A

Collagenase

Helps invasiveness

42
Q

What fungal infection is a hallmark of immunocompromised pts?

A

Pneumocystis jiroveci

43
Q

2 Examples of protozoa

A

Plasmodium falciparum

Trypanosoma cruzi

44
Q

An example of a fluke (helminth)

A

Schistosoma mansoni

45
Q

3 Mechanisms of resistance to antibiotics

A

1) Drug inactivation (e.g. Beta lactamases)
2) alteredTarget site i.e. Target enzyme may have lower affinity for drug (e.g. Meticillin)
3) Decreased uptake or increased efflux (tetracycline)

46
Q

3 methods of horizontal gene transfer between bacteria

A

1) conjugation - bacteria share plasmid via conjugation tube
2) transduction - bacteriophage introduces new genes from previous host
3) transformation- free dna comes in

47
Q

How to test for antibiotic sensitivity?

A

Disc sensitivity testing

May also want to measure min inhib concen

48
Q

5 betalactam examples in 5 seconds. Go!

A

1) penicillin
2) benzylpenicillin
3) amoxicillin
4) flucloxacillin
5) Co-amoxiclav (amoxicillin + clavulanate)
6) Tazocin (pipperacillin + tazobactam)

49
Q

Example of cephalosporin

A

Ceftriaxone

50
Q

Example of carbapenem

A

Meropenem

51
Q

Pt had infection which was treated successfully with penicillin. What’s most likely family of bacteria?

A

Streptococcus

Staph now resistant

52
Q

Pt suspected to have gram negative sepsis. What is your treatment of choice?

A

Ceftriaxone, because of CSF penetration, watch out c.dif

53
Q

Ideal features of an antibiotic?

A 
Selective toxicity
Few adverse effects
Reach site of infection
Oral/IV formulation
Long half life - infrequent dosing
No interference with other drug
54
Q

Amoxicillin main use

A

Gram positive, some gram neg.

55
Q

Flucloxacillin,

A

Staph

Strep

56
Q

Pseudomonas infection what antibiotic?

A

Tazacin

Pipperacillin and tazobactam

57
Q

Does co-amoxiclav work on anaerobes?

A

Yup

58
Q

Cephalosporins such as ceftriaxone do not work on anaerobes. True or false?

A

True

59
Q

You have a pt who is allergic to penicillin. Last time she took penicillin she threw up and didn’t feel too well. You now suspect she has an infection and are thinking of prescribing meropenem, which is a carbapenem. Is it safe?

A

Yes, unless she had anaphylaxis

60
Q

Facts about vancomycin, go.

A

1) G positive only
2) most staph
3) some enterococci resistant (VRE)
4) not absorbed, hence iv only - but oral for c dif
5) resistance in staph rare
6) TDM required (narrow therapeutic window)

61
Q

A patient comes in with a red, swollen leg that is tender and throbbing.

He most probably has cellulitis, so you start treatment with AB.

The blood culture however, comes back negative.

Is it possible to have an infection without a possitive blood culture?

A

Yes

Not all infections travel to blood

Some, such as this one, may be localised so a negative blood culture does not rule out cellulitis

Carry on AB and see how he does

62
Q

Pt sick after being admitted to hospital.

What is the criteria for healthcare infections?

A

Infections arising as consequence of providing healthcare

In hospital pts:

  • Neither present nor incubating at time of admission
  • Onset at least 48 hours post-admission

Also includes infections in hospital visitors and healthcare workers

63
Q

Give some examples of healthcare acquired infections

A

Blood borne viruses e.g. Hep. B, C, HIV

Norovirus

MRSA

Cdif

Pseudomonas aeruginosa

TB

64
Q

4 Ps of Infection Control

A

Patient

Pathogen

Practise

Place

65
Q

Have you I-fives your patient today?

A

Identify (Abroad, bbinfections, colonised, diarrhoea/vomiting, expectorating, funny looking rash)

Isolate
Investigate
Inform
Initiate

ESA3 (7 decks)

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