Lecture 12 Flashcards
(14 cards)
Emerging Bacterial Threats: Yersinia pestis (Plague)
Reservoir: Wild rodents are the primary carriers.
Forms of plague:
Pneumonic plague: Affects the lungs. Spread via droplets. Highly contagious and fatal if untreated.
Bubonic plague: Causes swollen lymph nodes (“buboes”). Spread by flea bites.
Septicemic plague: Bacteria in the bloodstream. Can develop from the other forms.
High fatality without rapid treatment
Emerging threats: Problems caused by biofilms:
Gum Disease: Dental plaque is a classic biofilm.
Medical devices:
Catheters (urinary or intravenous) – biofilms can block flow and cause infections.
Implants (e.g., joints, heart valves) – require surgical removal if infected.
Bacteriophage (Phage)
Viruses that infect and kill bacteria.
Extremely common – the most abundant lifeform on Earth.
Present in soil, water, animals’ intestines, etc.
Phage structure
Capsid (protein shell): encloses genetic material (DNA/RNA).
Genome can be: ssDNA, dsDNA, ssRNA, or dsRNA; circular or linear.
Collar and Core: structures supporting DNA injection.
Helical Sheath: contracts to push phage DNA into bacteria.
Tail spikes: used to attach to host bacteria.
Variation in length, capsid size, and tail presence.
Alternative Therapy: Phage Therapy
Phage therapy uses lytic bacteriophages to treat bacterial infections.
Especially useful when antibiotics fail (e.g., resistant infections).
Phage Sourcing & Isolation
Local environments with lots of bacteria (e.g. sewage)
Isolation Process:
Grow target bacteria in lab.
Introduce environmental sample.
Lytic phage infect and kill bacteria.
Filter to remove bacteria – retain pure phage solution.
Phage Therapy: Advantages over Antibiotics
Highly effective against target bacteria.
Co-evolve with bacteria – new phage can emerge to counteract resistance.
Self-limiting: phage stop multiplying once the infection is gone.
Can penetrate biofilms and deep tissues.
Environment-specific: Phages can be isolated from the same site as the infection.
Phage Therapy: Disadvantages and Challenges
Refrigeration required – not shelf-stable like some antibiotics.
Specialist training needed for doctors.
Difficult to treat polymicrobial infections (involving many bacterial types).
Solution: phage cocktails (mixtures).
Needs lab testing before use to ensure effectiveness:
Makes it unsuitable for acute/emergency infections.
High specificity:
Requires customized cocktails per region or patient.
Limited scope:
No lytic phage found for C. difficile (only temperate phage).
Delivery challenge: phages must reach infection site, which may differ from where antibiotics can reach.
Public perception: “viruses” can evoke fear and skepticism.
Phage Delivery Routes: Parenteral (non-oral)
Intramuscular (IM) Injection: Injection of phage directly into a muscle
Subcutaneous (SC) Injection: Injection of phage just under the skin, into the fatty tissue layer.
Intraperitoneal (IP) Injection: Injection of phage into the peritoneal cavity, the space within the abdomen that houses organs like intestines and liver.
Phage Delivery Routes: Oral
For gut infections, but must survive stomach acid.
Solution: microencapsulation.
Phage Delivery Routes: Local Application
Wound healing: hydrogel patches with phage (+ antibiotics).
Inhalation (nebulizer): lung infections.
Food Safety Uses of Phage
Raw meat: control Campylobacter.
Fresh produce: control Listeria.
Spoilage reduction.
Manuka Honey - Main components:
High sugar/osmolarity: draws water out of bacteria.
Hydrogen peroxide activity
Methylglyoxal (MGO): major antibacterial agent
Effective against ~80 bacterial species
Manuka Honey - targets and effects
Disrupts stress and membrane proteins in bacteria.
Decreases:
Quorum sensing: reduces coordination of bacterial behavior.
Siderophores: limits iron uptake.
Surface adhesion: prevents sticking to tissues.
Biofilms:
Inhibits formation
Disrupts existing biofilms
Reduces bacterial binding to human epithelial cells.
