Spread of pathogens within the host Flashcards
What are the different ways infection can spread?
–Pathogen from site of infection
•Via tissues -cell to cell
•Via cardiovascular system
–Arteries and Veins
•Via Lymphatic System
–Lymph ducts & Lymph nodes
–Two systems interconnected
Explain the two different ways pathogens can enter into the cardiovascular system?
–Direct
- Cut, Bite, Needle stick, Tooth extraction
- Intravenous needle use
–Indirect
- Lymph fluid -tissues
- via lymph ducts to venous system
What are the various sites in which pathogens can get access to the blood?
-intestinal tract: Salmonella spp
-Upper respiratory tract: Neisseria
meningitidis, Haemophilus
influenzae
-Lower respiratory tract: Strep. pneumoniae.
- Skin: wound
infection: S. aureus, Streptococci
-Urinary tract: E. coli, enterococci, Gonococci
Why is the lymphatic system useful to spread pathogens?
Once the pathogen enters into the lymphatic system it can use that system to spread to any part of the body.
What causes Rheumatic fever?
Strep viridansfrom tooth extract to Heart valves (endocarditis)
What is the cause of Meningitis?
Neisseria meningitidis
or Haemophilus
influenzae
from nasal/oropharynx to blood blood-brain barrier to meninges
What is the cause of Malaria?
Plasmodium falciparum or P. vivax from blood (bite) to liver.
What is the cause of Bubonic Plague?
Yersinia pestis which is spread through Rat flea bites into the blood
Secrets a gel like capsule that prevents phagocytosis
Lymph nodes swell (buboe) Giving it the name Bubonic Plague
Major organs like lungs causing pneumonic plague
Define Bacteraemia
Transient appearance of organism in blood
Define Septicaemia
Chronic high level growth in blood
Spreading in the blood: Explain Free
Exposed to host defence for example
Bacillus anthracis (Anthrax)
Leptospira sp (Wiel’s disease).
Spreading in the blood: Explain Intracellular
Protected from host defence
For example:
•Neisseria
gonorrhoeae, Mycobacterium tuberculosis,Listeria
monocytogenes
enter macrophages
•P. falciparumand P. vivaxin erythrocytes
What are the two different Herpes simplex virus’s spread through the Central nervous system? List some symptoms too
- Cold Sores -Herpes simplex virus (HSVI)
- Genital herpes -HSVII
–Skin fluid filled blisters
–Erupt
–Virus through tissues to peripheral nerves
–To CNS and Dorsal Root Ganglion
–Recurrent infection -stress.
–Virus returns to Skin by same route
What is the difference between Chicken Pox and Shingles?
They are both technically caused by the same virus, Varicella-Zoster virus.
For chicken pox it is named Varicella virus and for Shingles it is Zoster virus.
Chicken Pox is mostly seen in Children, however rarely in adults.
What causes Shingles in Adults?
Once a child has had Chicken pox the Pustules will heal VZV via the peripheral nerves dorsal root ganglion
The virus becomes latent until late adult life
VZV in adults moves along peripheral nerves to skin causing shingles
What is the cause Rabies?
Rhabdovirus
The virus enters the muscle tissue by infected saliva up to the peripheral nerves.
Along the main neural axons of CNS leading to the Brain
This then develops symptoms such as:
–Agitation
–Hydrophobia
Resulting in death due to fatal encephalitis / respiratory failure.
Protozoan: How does Naegleria fowleri effect the body?
This is a Aquatic amoeba which is found in natural springs, entering through body through the nose.
- Enters nose
- Spreads via olfactory nerve to olfactory centre in brain.
- Brain tissue damage and haemorrhage
•Acanthamoeba
castellani
contaminated tap water and/or saline washing contact lenses.
•Damaged cornea spread via optic nerve to brain.
Briefly explain Virion Assembly?
First the formation and assembly of capsid before the Association of viral genome with capid
briefly explain the two types of Release Assembly
One method is release by budding:
- Bud formation
- Bud growth
- Fusion of the bud membrane
- Speraration from the host
Another is from Cell lysis, the destruction of the cell to spread the virus around.
