Antimicrobial alternatives

Question 1

What are the current antibacterial alternatives?

Answer 1

Bacteriocins 
Phage therapy 
RNA silencing 
Natural remedies 
Probiotics 
Photodynamic therapy

Question 2

Why are alternatives being developed?

Answer 2

Due to increase in antibiotic resistance. The Golden Age of antibiotic discovery led to the production of antibiotics we use till this day. However, strains from many pathogens show resistance to most of these therapies so new methods have to be discovered.

We are at a void of discovery

Question 3

What does PDT entail?

Answer 3

The use of wavelengths of light to activate photosensitizer molecules and produce ROS.

These are toxic to bacteria.

Question 4

How do ROS kill bacteria?

Answer 4

Interfere with many processes like :

cell membrane production
DNA replication

Question 5

What are the advantages of PDT?

Answer 5

Broadly specific - kills all bacteria whether antibiotic sensitive or not
Does not create selection pressure
Many targets means the development of resistance is negligible
Localised short term treatment due to short lifespan of ROS

Question 6

Which conditions does ROS treat in present day?

Answer 6

Many conditions in the oral cavity - caries and peridontitis
MRSA in rats

Question 7

What are bacteriocins?

Answer 7

They are antimicrobial peptides produced by bacteria to inhibit neighbouring bacteria.

Produced in the ribosome, these allow the bacteria to outcompete with others for nutrients.

Question 8

Uses of bacteriocins

Answer 8

Nisin E234 - food preservative

Biofilm eradication - clinical trial

Question 9

How do bacteriocins kill bacteria?

Answer 9

Form pores on their CSM - reduce the membrane potential and leads to leakage of cell contents
Endonuclease activity - degrade chromosomes
Cell wall - sequesters lipid II (important precursor for peptidoglycan) or destroys proteins in the cell wall/in cell

Question 10

How can we use bacteriocins therapeutically?

Answer 10

Genetic manipulation of the 11 genes on operons required for functionality can produce novel variants with extended activity and different specificities.

Question 11

What are probiotics?

Answer 11

Probiotics use bacteria from commensal populations in our body to confer health benefits.

Question 12

How can bacteria from commensal populations lead to pathogen death?

Answer 12

Outcompete pathogens for nutrients/ space
Synthesise bacteriocins
Prevent adhesion to host cells

Question 13

Mechanism of probiotic therapy

Answer 13

Foecal transplantation has been 90% effective

Question 14

What is phage therapy?

Answer 14

The use of bacteriophages to treat bacterial infections. Viruses invade bacteria and cause cell lysis.

Question 15

Advantages of phage therapy

Answer 15

Narrow spectrum of activity - only affects one bacterial species/strain
Resistance can occur naturally but the phage can co-evolve to re-infect the phage-resistant bacteria

Question 16

Is phage therpay used therapeutically?

Answer 16

In Soviet Union yes - cheaper than antibiotics, Intestiphage and Prophage used

In UK and US - clinical trials for Intralytix used to heal wounds. Used comercially in food preservation.

Question 17

Natural remedies combating bacterial infections

Answer 17

Honey - low pH, H202, high glucose
Metal nanoparticles - wound healing
Tea tree oil - skin infections, deodorant and shampoos

Question 18

What is RNAi?

Answer 18

RNA interferance is a natural mechanism by which cells silence the expression of certain genes.

Question 19

What is the process of RNAi?

Answer 19

Two important RNA molecules are synthesised in our cells

siRNA (small interfering RNA)
microRNA

These work by binding to complementary strands on mRNA being translated and causes them to be cleaved off, essentially silencing their genes.

Question 20

Where is siRNA and microRNA made?

Answer 20

siRNA - cleaved from bigger RNA molecules or injected experimentally

microRNA - in the nucleus

Question 21

How do siRNA and microRNA become activated?

Answer 21

siRNA and microRNA bind to proteins in the cytoplasm and are cleaved.

They then tranfer to other proteins called Argonauts and form the RNA Induced Silencing Complex.

These RISC complexes then bind to complementary strands on the translated mRNA and causes their gene silencing.

Question 22

Is microRNA or siRNA more specific?

Answer 22

siRNA binds to the full complementary chain and so is more specific. microRNA only binds via a complementary portion called SEED and so is more broadly specific.

Question 23

Future of RNA silencing therapy

Answer 23

Since we can observe that certain RNA molecules are directed to produce gene silencing, we could manipulate this feature and inject siRNA experimentally to silence the genes coding for resistance.

Question 24

Hurdles of RNA therapy

Answer 24

Concentration of the oligonucleoside needed is unknown - must be high enough to sequester all target mRNA
Mechanism of resistance and genetic basis not known - need to know genes involved
Need to develop nucleotide carriers to protect oligonucleotide

Question 25

Future of antibiotics

Answer 25

Lots of research and development
Cost is high however
Due to this and development of likely resistance, drug companies are not interested

Question 26

How to make antibiotic market more attractive

Answer 26

Incentivise it