Infection And Immunity

Question 1

What is an infection?

Answer 1

An invasion of host tissues by micro-organisms

Question 2

3 mechanisms pathogen cause disease

Answer 2

Microbe multiplication
Toxins
Host response

Question 3

4 environmental sources for pathogen transfer

Answer 3

Food, air, water, surfaces

Question 4

Microbiota?

Answer 4

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

Question 5

How is legionella transferred?

Answer 5

Water droplets

Question 6

Modes of horizontal pathogen transfer

Answer 6

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

Question 7

Vertical pathogen transfer

Answer 7

Mother to child, at or before birth

Question 8

What do pathogens do once in ?

Answer 8

Exposure, adherence, invasion, multiplication, disemmination

Question 9

Virulence factors

Answer 9

Exotoxins - superantigens, AB toxins, enzymes, cytolytic

Endotoxins - LPS

Question 10

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

Answer 10

Pathogen - virulence, inoculum size, Ab resistance

Pt - site of infection, co-morbidities

Question 11

E.g. UTI by commensal

Answer 11

E. coli

Question 12

E.g Community acquired pneumonia

Answer 12

Streptococcus pneumoniae

Question 13

Eukaryotes have 80s ribosome, what about prokaryotes?

Answer 13

70s

Question 14

E.g. Gram neg, diplococcus

Answer 14

N. meningitidis

Question 15

Grape like cluster of coccus?

Answer 15

Staph aureus

Question 16

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

Answer 16

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.

Question 17

Example of unicellular fungi

Answer 17

Candida albicans

Question 18

Example of multicellular fungi

Answer 18

Aspergillus, dermatophytes

Question 19

What is a protozoa?

Answer 19

A single celled eukaryotic parasite

Question 20

What mechanism of action - beta lactams?

Answer 20

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

Question 21

What mechanism of action - glycopeptides?

Answer 21

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

Question 22

Example of glycopeptide?

Answer 22

Vancomycin

Question 23

Example of beta-lactam?

Answer 23

Penicillin

Amoxicillin

Question 24

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

Answer 24

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

Question 25

Two antibiotics that affect bacterial protein synthesis?

Answer 25

Tetracycline and doxycycline - NOT FOR KIDS

Question 26

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

Answer 26

Aminoglycosides - gentamycin Potentially nephrotoxin TDM (therapeutic dose monitoring required)

Question 27

Erythromycin and clarithromycin are types of?

Answer 27

Macrolides, inhibitors of protein synthesis

Question 28

Ciprofloxacin works by inhibiting nucleic acid synthesis. How?

Answer 28

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

Question 29

Give one mechanism by which bacteria can be rsistant to penicillin

Answer 29

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

Question 30

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

Answer 30

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

Question 31

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

Answer 31

``` Full blood count - neutrophils, lymphocytes CRP LFTs, KFTs Imaging - xray, ultrasound, MRI Histopathology ```

Question 32

How would you check if a pt had a virus?

Answer 32

Virology Antigen detection Antibody detection Nucleic Acid detection - DNA/RNA

Question 33

Virus basic structure

Answer 33

Nucleic acid, protein coat +/- LPS/lipid capsule, spikes

Question 34

What is the baltimore classification of viruses?

Answer 34

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

Question 35

Example of dsDNA non-enveloped viruses

Answer 35

Adenovirus, | Human papilloma virus

Question 36

DsDNA enveloped virus

Answer 36

Herpes virus Hep B Molluscum contagiosum

Question 37

Example of RNA virus

Answer 37

Hep A, E Influenza Norovirus

Question 38

Bacteria basic structure

Answer 38

Circular DNA, Plasma membrane Cell wall Ribosome +/- envelope, pili, flagellum, plasmid

Question 39

2 example of gram positive bacilli

Answer 39

Listeria monocytogenes Bacillus anthracis Bacillus cereus

Question 40

Examples of gram neg bacilli

Answer 40

Salmonella typhi Escherichia coli Haemophilus influenzae

Question 41

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

Answer 41

Collagenase | Helps invasiveness

Question 42

What fungal infection is a hallmark of immunocompromised pts?

Answer 42

Pneumocystis jiroveci

Question 43

2 Examples of protozoa

Answer 43

Plasmodium falciparum | Trypanosoma cruzi

Question 44

An example of a fluke (helminth)

Answer 44

Schistosoma mansoni

Question 45

3 Mechanisms of resistance to antibiotics

Answer 45

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)

Question 46

3 methods of horizontal gene transfer between bacteria

Answer 46

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

Question 47

How to test for antibiotic sensitivity?

Answer 47

Disc sensitivity testing | May also want to measure min inhib concen

Question 48

5 betalactam examples in 5 seconds. Go!

Answer 48

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

Question 49

Example of cephalosporin

Answer 49

Ceftriaxone

Question 50

Example of carbapenem

Answer 50

Meropenem

Question 51

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

Answer 51

Streptococcus | Staph now resistant

Question 52

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

Answer 52

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

Question 53

Ideal features of an antibiotic?

Answer 53

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

Question 54

Amoxicillin main use

Answer 54

Gram positive, some gram neg.

Question 55

Flucloxacillin,

Answer 55

Staph | Strep

Question 56

Pseudomonas infection what antibiotic?

Answer 56

Tazacin Pipperacillin and tazobactam

Question 57

Does co-amoxiclav work on anaerobes?

Answer 57

Yup

Question 58

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

Answer 58

True

Question 59

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?

Answer 59

Yes, unless she had anaphylaxis

Question 60

Facts about vancomycin, go.

Answer 60

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)

Question 61

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?

Answer 61

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

Question 62

Pt sick after being admitted to hospital. | What is the criteria for healthcare infections?

Answer 62

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

Question 63

Give some examples of healthcare acquired infections

Answer 63

Blood borne viruses e.g. Hep. B, C, HIV Norovirus MRSA Cdif Pseudomonas aeruginosa TB

Question 64

4 Ps of Infection Control

Answer 64

Patient Pathogen Practise Place

Question 65

Have you I-fives your patient today?

Answer 65

Identify (Abroad, bbinfections, colonised, diarrhoea/vomiting, expectorating, funny looking rash) Isolate Investigate Inform Initiate