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
