1. Respiratory Route

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  1. parts of the respiratory tract
    • upper respiratory tract =
    • nasal cavity
    • pharynx
    • larynx

    • lower respiratory tract =
    • trachea
    • primary bronchi
    • lungs
  2. defenses of the respiratory tract
    • hairs in nose filter out large particles
    • coughing and sneezing expel particles
    • lyzozyme in saliva
    • mucociliary escalator
    • epithelial barrier
    • respiratory mucus secreted by goblet cells
    • phagocytic cells (macrophages)
    • local production of antibodies
    • endogenous organisms - LRT is normally sterile, URT contains bacteria
  3. mucociliary escalator
    goblet cells produce a layer of mucous over cilia that push particles up out of the respiratory tract
  4. impaired host defenses
    • smoking
    • inhaled pollutants or dust
    • impaired cough and gag reflexes
    • advanced age
  5. transmission
    • mostly through respiratory route
    • coughing and sneezing produce large number of droplets
    • droplet infection
    • close contact sometimes required
    • fomites often play a role
  6. means of exposure to infectious secretions
    • small-particle aerosols (droplet nuclei):
    • capable of distant spread close
    • contact not required
    • rapid outbreak of cases

    • large-particle droplet aerosols:
    • close contact necessary
    • spread may be slow and without clustering of cases and may go unrecognized

    • fomites with self inoculation:
    • direct contact with infectious secretions contaminating environmental surfaces required
    • transferred from hands to mucosa
    • spread among those with close and prolonged contact with infected individual and among those with poor hygiene
  7. the common cold etiology
    • rhinovirus (most common in children and adults)
    • coronavirus (most common in adults)
    • respiratory syncytial virus (most severe in infants)
    • parainfluenza
    • influenza
    • adenovirus
    • human metapneumovirus
    • human becavirus
    • occasionally bacteria
  8. rhinovirus
    • most common cause of cold
    • ssRNA virus
  9. rhinovirus transmission
    • aerosol
    • person to person
    • fomites
  10. rhinovirus communicability
    • viral shedding highest at beginning of symptoms
    • inapparent to apparent disease ratio 3:1
  11. rhinovirus pathogenesis
    • infect respiratory epithelial cells in nasal cavity
    • lytic infection destroys cells
    • infection and destruction of cells induces inflammation (causes symptoms)
    • does not proceed lower in the respiratory tract because they are temperature sensitive
    • immune response - from mucosal antibodies
  12. rhinovirus clinical
    • pain in nasal cavity, nasal congestion, runny nose, sneezing, sometimes cough
    • accompanied by muscle aches, fatigue, headache, loss of appetite
  13. rhinovirus diagnosis
    clinical, based on signs and symptoms
  14. rhinovirus treatment
    only palliative not curative - anti-inflammatories or antihistamines, zinc lozenges
  15. rhinovirus prevention
    • wash hands
    • avoid those who are sick
    • vaccine difficult because so many serotypes
  16. pharyngitis (sore throat) etiology
    most caused by viruses - slower onset, less severe, clinical diagnosis, palliative treatment, avoid close contact

    more severe caused by streptococcus pyogenes (strep throat)
  17. streptococcal pharyngitis etiology
    • streptococcus pyogenes - also A beta-hemolytic streptococcus
    • gram + cocci in chains
    • also causes skin and tissue infections
  18. streptococcal pharyngitis occurrence
    most common cause of bacterial pharyngitis in children, one of most common bacterial infections of childhood
  19. streptococcal pharyngitis transmission
    person to person via droplets, crowding favors spread
  20. streptococcal pharyngitis communicability
    asymptomatic carriage may facilitate spread of disease
  21. streptococcal pharyngitis pathogenesis
    • adherence with pili
    • M protein and carbohydrate resist initial opsonization and phagocytosis
    • toxins important - streptolysins, streptococcal pyrogenic exotoxins
    • immune response is effective - antibodies produced against M protein opsonize bacteria and enhance phagocytosis, neutralizing antibodies against toxins
  22. streptococcal pharyngitis clinical
    • acute onset
    • severe soreness of throat
    • infected area of throat usually fiery red
    • swollen lymph nodes
    • fever
    • can spread to middle ear and cause ear infections
  23. streptococcal pharyngitis complications
    • scarlet fever
    • acute rheumatic fever
    • rheumatic heart disease
    • glomerulonephritis (kidney inflammation)
  24. streptococcal pharyngitis diagnosis
    • gram stain
    • hemolysis - B-hemolytic
    • strep enzyme test
    • lab diagnosis - crucial for accuracy
  25. streptococcal pharyngitis treatment
    • beta-lactam antibiotics - penicillin
    • immune response is sufficient, but treatment is crucial- hastens recovery, alleviates sore throat, prevents sequelae
  26. streptococcal pharyngitis prevention
    • avoidance of close contact
    • hygiene
  27. infectious mononucleosis etiology
    • epstein barr virus
    • dsDNA virus in herpes family
  28. infectious mononucleosis occurrence
    • worldwide
    • in most of world children get infected at young age and rarely develop disease
    • in developed countries, infection is sometimes delayed, disease more likely
  29. infectious mononucleosis transmission
    respiratory route - virus in saliva, requires intimate contact
  30. infectious mononucleosis communicability
    virus can be shed for months after symptoms end
  31. infectious mononucleosis pathogenesis
    • primary infection (lytic) - virus replicates in epithelial cells of pharynx, enters B cells and spreads throughout body
    • persistent infection (lysogenic) - activates newly infected B cells to induce differentiation into memory cells, become latent
    • immune response - both humoral and cellular, neutralizing antibodies and cytotoxic T cells against infected B cells
  32. infectious mononucleosis clinical
    • sore throat, rash, lymphadenopathy, fever, extreme fatigue
    • also involve in cancers
    • may be involved in multiple sclerosis
  33. infectious mononucleosis diagnosis
    • clinical
    • blood work
    • serological tests
  34. infectious mononucleosis treatment
    • bed rest
    • palliative treatment for fever, pain
    • can use acyclovir steroids
  35. infectious mononucleosis prevention
    avoidance, but very difficult (subclinical carriers)
  36. dental carries (tooth decay) etiology
    • most important is streptococcus mutans
    • gram+ cocci
  37. dental carries (tooth decay) transmission
    • infants acquire organism soon after birth
    • everyone has it, transmission not relevant
  38. dental carries (tooth decay) pathogenesis
    • plaque theory:
    • bacteria form dextran from sucrose in saliva
    • dextran coats teeth making surface sticky and bacteria stick to this forming plaque
    • organisms become cemented to teeth at one spot
    • bacteria produce acid which eats hole in tooth enamel
    • immune response poor because no blood flow
  39. dental carries (tooth decay) diagnosis
    • clinical based on signs
    • x-rays
  40. dental carries (tooth decay) treatment
  41. dental carries (tooth decay) prevention
    3 factors: susceptible teeth, bacteria, sugar

    • prevention strategies:
    • reduce sugar intake
    • reduce bacteria and plaque by brushing, flossing, mouthwash
    • increasing hardness of tooth enamel through flouridation
Card Set
1. Respiratory Route
public health microbiology midterm 3 lecture 1
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