Respiratory Infections

Question 1

What is the function of the respiratory tract?

Answer 1

-perform respiration
-the exchange of oxygen and carbon dioxide
-deliver air from outside of the body to the alveoli where gas exchange occurs
-the components of the respiratory tract participate in defending itself against infection

Question 2

What comprises the upper respiratory tract?

Answer 2

1. nasal cavity
2. pharynx (nasopharynx, oropharynx, laryngopharynx)
3. larynx
4. trachea
5. left and right primary bronchi

Question 3

What comprises the lower respiratory tract?

Answer 3

1. right pleural cavity
2. bronchioles
3. mediastinum
4. left pleural cavity
5. pleural space
6. diaphragm

Question 4

What are some natural host defenses?

Answer 4

-nasal hairs
- convoluted
-mucus
-antibacterial substances: lysozyme IgA
-normal flora of upper tract
-cilia and mucus of trachea
-coughing, sneezing, swallowing

Question 5

What is the normal flora of the oropharynx?

Answer 5

-strep pneumo
-strep pyogenes
-nonhemolytic strep
-veillonella
-Bacteroides
-fusobacterium
-prevotella
-porphyromonas
-coag neg staph
-Neisseria
-micrococcus
-eikenella
-capnocytophaga
-candida
-H flu/ H paraflu
-peptostreptococcus
-actinomycetes

Question 6

Routes of transmission for pathogens

Answer 6

-colonization of potential pathogens in the upper respiratory tract
-aspiration of resp secretions
-droplet inhalation
-hematogenous spread into the pleural space
-alteration of normal flora

Question 7

Host risk factors

Answer 7

1. immune status of the host (previous exposure)
2. Age (infants, young children, and elderly are more likely to develop complications)
3. reduced clearance of secretions (immature anatomic development, transient reduction and function of mucociliary mechanism, obstruction by foreign body)
4. Infection-induced airway obstructions (inflammatory response due to infection)

Question 8

Seasonal and community trends

Answer 8

-certain respiratory tract pathogens have peak seasonal incidence (viral infections are more common in the winter)

-other respiratory tract pathogens occur year-round (mycoplasma pneumonia is responsible for 50% of cases of pneumonia in the summer)

-empiric antimicrobial therapy (when necessary it is important to have a working knowledge of the microorganisms likely to cause an infection)

Question 9

What are some virulence factors?

Answer 9

1. adherence
   * attachment of pathogen to host tissue (or organelles such as lipoteichoic acids, M proteins, and fimbriae)
2. Toxin elaboration
   * pathogens produce toxins that interfere with the normal activity of the host (coryne diptheriae toxin interferes with protein synthesis)
3. Evasion of host defenses
   *may express polysaccharide capsules preventing phagocytosis by host WBCs
   *intracellular pathogens are protected from the host immune system

Question 10

Upper respiratory infection

Answer 10

-involve infections in the nasal cavity and sinuses, nasopharynx, oropharynx and the larynx
-mostly viruses, but can be caused by bacteria

Question 11

What can cause pharyngitis in children and adults?

Answer 11

children: streptococcus pyogenes
adults: viruses

Question 12

What causes epiglottis?

Answer 12

H. influenzae type B
-streptococci
-staphylococci

Question 13

Rhinitis

Answer 13

-common cold
-inflammation of the nasal mucosa

viruses: Rhino, Corona, Adeno, Influenza/parainfluenza, RSV, Entero

Bacteria: (rarely) clamydophila pneumonia, mycoplasma pneumonia, strep pyogenes

Question 14

Laryngitis

Answer 14

-hoarseness
-lowering of the voice with exudate on the laryngeal mucosa
Viruses: rhino, adeno, influenza

Question 15

Laryngotracheobronchitis

Answer 15

-croup
-non-productive barking cough, resp distress, in young children usually
-caused by the parainfluenza virus