Phage therapy and virulence Flashcards
Phages 6 facts
- Bacterial viruses
- Dominant life form on earth
- Different forms : Small dots (bacteriophage particles) , Medium dots (Prokaryotic cells) , Two large objects (Protists/ Diatom cells)
- Use different receptors ( endotoxin LPS, outer membrane proteins, Flagella, Pili)
- Very specific, terwijl antibiocitcs kill a lot around
- Are ubiquitous (are everywere in bacteria)
Infection cycle
5 steps
- Virus binds host specific
- Brings its genomic materical in host cell (RNA or DNA)
- Reprogramming host cell: Change host cell
- Host cell will make virus proteins
- Lysis and escape bacteria»_space; Phage particles relates and can infect new cell
Plaque
2 facts
Colony of phages
They are homogeneous and tell something over the type.
2 types of multiplication in host
- Lytic : Genomic introduced by phage > Lysis bacteria
- Used for phage therapy
- 90% phages is lytic - Lysogenic cycle : Phage integrates in bacterial genome (specific enzyme) > Prophage can be silent and given to daughter cells, is’t verspreid over whole genome.
- Can spread virulence and resistance genes.
- This lysogenic cycle of integrating phages is an evolutionary advantage for bacteria.
«< If bacterial has stress than it releases and go to lytic cycle.
Phages and bacteria in everlasting battle.
3 Defence mechanisms of bacteria
Innate
- Restriction enzymes mechanism, Cleave DNA of phage)
- Receptor modification Attachment inhibition
Adaptive
- Cripsr-Cas :
- Holds viral DNA in it’s own DNA at CISPR.
Cocktails of phages needed
4 reasons
- Even when infection caused by single species
- Target all strains of species
- Variation in E.coli strains (you have to kill them all) «_space;Mostly 10-20 phages needed
- Avoiding resistance
- Different kind of phages to kill
Advantages Phages therapy
9 reasons
- Highly specific: Kill what you want to kill
- Replication at the site of infection
- Active in biofilms
- Safe but make sure endotoxin is removed
- Help antibiotics to kill better
- Evolution is possible (=cause they are living species) > Counteract resistance
- Easy to get high number of phages
- Just one phage has to reach infection to kill bacteria
- Small and get relative easely through tissue
Disadvantage of phage therapy 7 reasons
- Not applicable for intracellular pathogens
- Not functional against dormant bacteria
- Formulation difficult (Aren’t stable)
- Highly specific (advantage / disadvantage)
- Difficult to get patent: IP rights
- Difficult to get approval
- Virtually impossible to get big pharma interested
Dormant bacteria
Inactive bacteria, phages kill only growing bacteria
Reticulo endothelial system
Liver with kuppfer cell fish out everything that shouldn’t be in bloud. 1% survival after 60 minutes injection
Route through stomach
If given orally > Acids of stomach affect phages
Long circulation mutants of phages (improved phages)
- Inject large number of phages in mice
- Isolate phages after 7 hours
- Grow the phages on bacteria
- This 4 thimes»_space; Long circulating bacteria
Studies on phages
2 animal studies
2 human studies
- Animal experiments
(Mice with luciferase and p.aeruginosa, mice with phages less light, because growth stopped)
(Mice with lethal dose of E.coli , only mice with phages survived) - Clinical study
(Treated against P. aeruginose with 6 different phages 25% effect, not a big succes)
(Treat burn wounds, very difficult to treat with antibiotics, Difficulties: Showing stability of phage cocktail and Only patients with one single infection can be used)
Alternative for phages
To agricultural/ food / cleaning industry because rules are more relaxed.
Problems to reach tissue
- Routing throug stomach: formulation
- Reticulo-endothelial system
The surface charge of phages need to be neutral < Because important for fish out.
