Mechanisms of infectious diseases Flashcards
Commensal Flora
- Over 300 different species of bacteria live in the large intestine
- Bacteria and fungi live on our skin
- Mouth and pharynx contain many bacteria
- Vagina contains acid-producing bacteria
Compare and Contrast Mutualism and Parasitic
Mutualism:
Both the host and microorganism benefit
Parasitic:
- Only infecting organism benefits
- Typically host doesn’t die
- Infectious means host sustains injury
Terminology
1. Virulence Disease producing potential 2. Pathogen Very virulent microorganisms 3. Saprophyte Environmental organisms that feed off dead/decaying organic material Usually fungi Harmless to humans, but can be opportunisitic organisms if host immune system is compromised
Agent of Infection: Prions
- Abnormally shaped proteins that cause normal proteins to change their shape and thus become new prions
- Propagation is unclear so difficutly to treat
- Doesn’t reproduce, but uses existing protein
- Cause neurodegenerative diseases of CNS
e. g. Creutzfeldt jakob disease
Viruses
- Small, no organized cellular structure
- Incapable of replicating outside a living cell
- Protein coat surrounded by a nucleic acid core
- Some have lipoprotein envelope
- Inserts genome into host cells DNA, then uses cells energy
- Grouped by size, composition, how it replicates/transmits, resulting disease, etc.
Compare latent and oncogenic viruses
- Latent viruses
Enter cell insert genome, remain dormant until stimulated
- Varicella zoster, Epstein-Barr virus, herpes - Oncogenic viruses
- Can transform host cells to malignant cells during replication
Human papillomavirus (HPV)
Epstein-Barr, Hep B
Compare influenza, retrovirus, and enterovirus
- Influenza viruses
- H1N1, H3N2 - Retrovirus group
- Unique replication
- HIV/AIDS (unique replication) - Enterovirus
- Single stranded RNA virus
- Found in mucous, saliva, stool of infected person
- Poliomyelitis
Bacteria and it’s characteristics
- Small, simple structure
- Cytoplasm covered by rigid cell wall that is susceptible to anti-bacterials
- Can live independently, but uses organism’s nutrients
- Contains both RNA & DNA
- Flagella: propel bacteria
- Pili: filaments that help adherence
Bacteria shapes/types and definitions
- Streptococci: divide into chains
- Diplococci: divide into pairs
- Staphylococci: divide into clusters
- Biofilm = structured community of bacteria
- Spores = group waiting for favorable conditions to replicate
- Aerobic = requires oxygen
- Anaerobic = hates too much oxygen
- Facultatively anaerobic = can adapt to oxygen rich or poor environment
Types of bacteria con’t
Gram positive/Gram negative
- Stain red/blue
Acid-fast bacilli = don’t stain
Spirochets: helical, long bacteria
Mycoplasms
Smaller than normal bacteria
Resistant to some antibiotics
Organisms having both viral and bacterial characteristics
- Rickettsiaceae
- Carried by fleas, ticks, lice
- Need host nutrients & cell ATP byproducts
eg: rocky mountain spotted fever, typhoid fever - Chlamydiaceae
- STI
- Ocular infection in newborn
- Respiratory infections
Fungi
-Only a few cause serious disease
-Require temperature < body so usually on surface
-Often self-limiting
-Not susceptible to penicillin-like antibiotics
Yeasts: waxy/creamy texture
Molds: cottony/powdery colonies
Parasites & Transmission
Protozoa (unicellular animals) Transmission Host to host (sexual contact) Arthropod vector Contaminated food/water
Malaria, dysentery (both parasites)
Helminths (wormlike) parasite
-Roundworms, tapeworms, flukes
-Any body organ (or numerous)
e.g. intestinal parasites
Transmission:
-Ingestion of fertilized ova
-Penetration thru skin (arthropod vector)
Arthropod parasite
Ticks, mosquitoes, flies, mites, scabies, lice, fleas Transmission - clothing/bedding/combs/brushes Bubonic plague (fleas) Epidemic typhus (lice)