OBJ - Intro to Pathogens

Question 1

Compare and contrast key features of the different categories of infectious agents that cause human disease: bacteria, viruses, fungi, viruses, and prions.

Answer 1

Bacteria
Unicellular prokaryotes - no organelles
Rods or cocci &
Gram + = blue with thick peptidoglycan cell wall
Antibiotics are very effective
Gran - = pink thin cell wall with outer membrane

Viruses
Smallest infectious particle - only nucleic acid
DNA OR RNA + proteins for replication
Can be enclosed in a protein coat and/or lipid membrane
TRUE parasite - needs a host cell

Fungi
Eukaryotic organisms with organelles (harder to target them without harming human cells)
Exist as yeast or mold or both (dimorphic)
Ex: yeast infections & thrust

Parasites
Complex eukaryotes
Cary greatly in size from unicellular to mulitcellular/10m long

Prions
Small proteinacious infectious particles
Mutant form of a host protein
Resistant to chemicals, heat & ionizing radiation
Ex: mad cow disease

Question 2

Outline the steps required for establishment of infectious diseases

Answer 2

Encounter Host defenses have to be breached at every step
Exogenously/endogenously
ntry
Remains on mucosa after inhalation/ingestion
Penetrates mucosal/skin barrier (ex: cut, bite, blood transfusion)

Spread
Initial inoculum size matters & is organism/site of entry dependent

Multiply
Must meet threshold to “win the war” and cause symptoms

Damage
Tissue destruction, toxins, immunopathology

Outcome

Question 3

Differentiate between exogenous versus endogenous causes of infectious diseases.

Answer 3

Exogenously acquired - acquired from an external source, newly introduced
Food, Water, Air, Objects (Noro), Insect bites, other humans, animals
Eyes, nose, mouth, respiratory tract, GI, genital tract, urinary tract

Endogenously acquired - from microbes present in/on the body as normal flora
Becomes out of balance (GI/vaginal)
Leaks out - trauma -> GI contents leak

Question 4

Relate the sites in the human body that are colonized by normal microbial flora

Answer 4

Skin
Respiratory tract - nose/throat
GI - mouth & large intestine
Genital tract - vagina

Question 5

Explain the critical role of normal human flora in health and disease states

Answer 5

Everyone has a fairly stable microbiome, but a lot of variation between individuals

@various body sites - very similar across humans but very different between body sites (vagina vs mouth)

Critical roles: Keeps out invaders, role in nutrition/metabolism, immune stimulation = moslty protective