Lecture 8 - Intervention and Prevention

Question 1

What are the three types of vaccine?

Answer 1

• The pathogen killed
• Live attenuated strain (disabled)
• Antigenic components of pathogen

Question 2

What is the disadvantage of using the killed pathogen?

Answer 2

Killing can change antigenic structure of proteins

Question 3

How can you make a live attenuated strain?

Answer 3

Use a mutant that cannot survive long with out a certain product you give it while it is in the lab

Question 4

What kind of proteins are used as vaccines?

Answer 4

• Only ones that are expressed during host infection cycle
• Must be antigenic
• Immune system has to see them (outer membrane proteins are good for this)
• Inactivated toxins (toxoids)

Question 5

What carbohydrates can be used as vaccines?

Answer 5

• O-antigen (LPS) on gr- bacteria

- capsule

Question 6

What structure does the LPS take? (from membrane)

Answer 6

Lipid A tail
Core
O antigen repeat

Question 7

What does the O antigen repeat consist of?

Answer 7

Sugars - galactose, mannose, aboquose

Repeated 20-50 times

Question 8

How can you assess drugs?

Answer 8

Live imaging by adding lux gene into bacteria and use Xenogen machine to detect light

Question 9

Whats the problem with using carbohydrates as vaccine?

Answer 9

They are normally not very antigenic and must find a way to couple it to a protein

Question 10

How many serogroups does Neisseria meningitidis have and what is the different between them?

Answer 10

five

carbohydrate identity

Question 11

What is the vaccine for four of the serogroups of Neisseria m?

Answer 11

Capsular polysaccharide

Question 12

Why is the vaccine for serogroup B of Neisseria different to the rest?

Answer 12

It’s capsule has polysialic acid which is like human cells.

This is poorly immunogenic and risks autoimmunity

Question 13

What is the vaccine for Serogroup B of Neisseria what is it made from?

Answer 13

4CMenB
1 adhesin
H binding protein
Heparin binding protein
2 additional antigens

Question 14

What is reverse vaccinology?

Answer 14

Start with the pathogen and use genomics to look for cell surface markers (signal sequence - hydrophobic stretch) and see what the immune response may recognise

Question 15

What steps are involved in reverse vaccinology (particularly 4CMenB)

Answer 15

• 2000 proteins identified to be surface
• purified protein tested for potential to induce bactericidal antibodies
• purified protein used to immunise mice
• antibody response analysed by ELISA
• prioritised based on ability to induce protection against a diverse collection of strains (5)

Question 16

What is an example of vaccination that has not gone to market and why could it be?

Answer 16

FimH vaccine

FimH has a lot of antigenic variation so may not be effective

Question 17

How has M. tubercolosis’ antibiotic resistance changed?

Answer 17

From 2000 to 2011 it’s resitance to any first line drug increased by 84%
Multidrug resitance increased by 189% since 2000.

Question 18

What are the 3 main targets of current antibiotics?

Answer 18

Cell wall synthesis
Ribosome
DNA gyrase/topoisomerase

Question 19

What is DNA gyrase?

Answer 19

Helps in DNA supercoiling where the helicase separates it

Question 20

Which antibiotics target the ribosome and what part of it?

Answer 20

Chloramphenicol - 50S

Tetracycline - 30S

Question 21

What do beta lactams inhibit and what are two examples of them?

Answer 21

Inhibit transpeptidation

Ampicillin and pennicillin

Question 22

What do glycopeptides inhibit and what is an example of one?

Answer 22

Inhibit transglycosylation

Vancomycin

Question 23

How do glycopeptides work?

Answer 23

bind to cell wall subunit and prevent incorporation into peptidoglycan

Question 24

How do beta-lactams work?

Answer 24

inhibit enzymes (PBPs) required for cross linking of chains which is the last step of cell wall synthesis

Question 25

What are metabolite analogs and give 2 examples,

Answer 25

Antibiotics that inhibit synthesis of nucleic acid precursors Sulfonamides Trimethoprim

Question 26

How do sulfonamides work?

Answer 26

Competitive inhibitor with PABA for enzyme to make folic acid Humans must take up folic acid so is not toxic

Question 27

How does trimethoprim work?

Answer 27

It is a structural analog of folic acid so inhibits enzyme. | Has a higher affinity for bacterial enzyme than human so not toxic

Question 28

How do you test bacteria for resistance to concentrations of antibiotic?

Answer 28

An E-test strip has dilutions of drugs down it | MIC (minimum inhibitory concentration) is measured on lowest concentration of no growth

Question 29

What are the 4 mechanisms of antibiotic resistance?

Answer 29

Modifying antibiotic target Limiting antibiotic in cell (reduced penetration or increased efflux) enzymatic inactivation Bypass pathway (another way to make product)

Question 30

How have bacteria generated resistance to beta-lactams? (2 ways)

Answer 30

``` Produce beta-lactamase to degrade Alter PBP (pencillin binding protein) so beta-lactam can not interact with it ```

Question 31

How have bacteria generated resistance to Vancomycin?

Answer 31

``` Altered target (peptidoglycan) D-ala-A-ala changed to D-ala-D-lactate ```

Question 32

What are two ways a strain acquires resistance? (genetic)

Answer 32

Horizontal gene transfer | Mutations

Question 33

What is a mechanism for multidrug resistance?

Answer 33

An efflux pump upregulated

Question 34

Why did Brockhurst (2012) use genomics to look at multidrug resistance in Salmonella?

Answer 34

In Africa many strains of S. gastroenteritis were starting to look like invasive S. typhi

Question 35

What did Brockhurst (2012) show had happened to confer multidrug resistance in this strain of Salmonella?

Answer 35

Transposon lead to clonal replacement and expansion of pSLT virulence plasmid. Gene deletion from gastroenteritis and acquisition of chloramphenicol resistance.

Question 36

What is a feature of persisters?

Answer 36

Large heterogeneity (lots of different ways to become resistant)

Question 37

What disease can be caused by antibiotics and how?

Answer 37

Clostridium difficile causing diarrhoea. | Antibiotics kill off healthy microbiome so C. difficile grows and produces toxin

Question 38

What some other ideas for stopping disease?

Answer 38

Affect virulence process - block or inactivate toxins | Block development of pathogenic phenotype (eg quorum sensing)

Question 39

What did Hentzner and Giskov find in 2003?

Answer 39

Furanone treated P. aeruginosa biofilms are less tolerant to tobramycin. However in 2013 found 3/8 strains not affected

Question 40

What are the stages of clinical trials?

Answer 40

Lab studies Human safety - 10s of people Expanded safety - 100s Efficacy and safety - 1000s