15.Microbial ecology

15.Microbial ecology

1. 1. symbiotic relationships btw microbes and hosts

   • symbyosis
     • Mutualism
     • Commensalism
     • Parasitism
   • Acquisition
     • during childbirth
     • first few months
       • From the moment we start contact with other people, we are being colonized by their microbiota
   • 2 types
     • Resident microbiota
       • thtoughout life
       • mostly commensal
       • all over mucose mb.
     • Transient microbiota
       • only for a while, cannot persist
         • competition
         • elimination
         • changes in body
   • normal microbiota-> opportunistic
     • causes
       • immune supression
       • changes in the normal microbiota
       • introduction of NM in unusual body parts

2. 2. Reservoirs of infectious diseases in humans

   • 3 types
     • animal
       • zoonoses
         • direct contact
         • eating animals
         • bloodsucking arthropodes
     • human carriers
       • asymptomatic but infective
       • some get sick, but some not
       • if healthy, defensive systems protect
     • nonliving
       • soil, water, food
       • contamination
         • feces/urine

3. 3. Movement of microbes into hosts: Infection

   • exposure to microbes
     • contamination
       • presence of microbes
     • infection
       • microbe establishes
   • Portals of entry
     • 4 major
       • skin
         • usually acts as a barrier
           • can enter through cuts
           • can make cuts by degrading
       • mucous mb
         • lines all cavities open to environment
         • provides good environment for pathogens
         • most common respiratory tract
         • if able to durvive acidic pH, throug GI
       • placenta
         • some pathogens can go through
         • some
           • protozoa
             • Toxoplasma gondil (Toxoplasmosis )
           • bacteria
             • Treponema pollidium (Syphilis)
             • Listeria monocytogens (Listeriosis)
           • DNA viruses
             • Cytomegavirus (asymptomatic)
             • Parvovirus B19 (Erythema infectiosum)
           • RNA viruses
             • HIV (AIDS)
             • Rubivirus (German measles)
       • parenteral route
         • not a true route

4. 4. Nature of infectious diseases

   • Virulence factors of IA
     • Pathogenecity
     • virulence
       • factors
         • Adhesion factors
           • adhesion: attachment to cell
           • required to establish colonies
           • attachment proteins (adhesins in bacteria)
         • biofilms
         • extracellular enzymes
           • by pathogen
           • dissolve chemicals in body and help w/ infection
           • avoid body's defense
         • toxins
           • chemicals that harm tissues
           • toxemia
           • 2 types
             • endotoxins
             • exotoxins
           • classification
             • place of damage
               • neurotoxins
               • enterotoxins
               • cytotoxins
             • • A-B toxins
               • mb interfering toxins
               • superantigens
         • antiphagocytic factors
           • bacterial capsule
             • chemicals not recognized as foreign
             • slippery, dificult to engulf
           • Antiphagocytic chemicals
             • prevent fusion of lysosome with p. v.
             • leukocidins
               • destroy phagocytic WBC
   • disease=morbidity
     • defense
       • innate (1st and 2nd line of defense)
       • adaptive
         • naturally
         • artificially acquired
     • stages: disease process
       • incubation period
       • prodromal period
       • Illness
       • Decline
       • Convalescence
     • manifestations
       • symptoms
       • signs
       • syndrome
       • asymptomatic

5. 6. Modes of infectious disease transmis

   • from reservoir to portal of entry
   • 3 groups
     • Contact transmission
     • vehicle transmission
     • vector transmission

6. 5.Portals of exit

   • many same as portals of entry
   • pathogens leave through
     • secretion
     • excretion

7. 7. Classification of infectious disease

8. 8. Epidiemology of infectious disease