Respiratory System Infections

Question 1

Streptococcal Pharyngitis (Strep Throat)

Answer 1

Caused by: Streptococcus pyogenes
Signs & Symptoms: sore throat, difficult swallowing, fever
Pathogenesis: M protein - important adhesin (prevents opsonization)
C5a peptidase - destroys C5a
Streptolysins S and O - make holes in erythrocytes and leukocytes
streptococcal pyrogenic exotoxins - cause high fever
hyaluronic acid capsule - disguise
Spread by: respiratory droplets
Post-Streptococcal Sequelae: complications occuring after infection, rheumatic fever

Question 2

Diphtheria

Answer 2

Caused by: Corynebacterium diphtheriae (gram-positive, diphtheria toxin, gene carried by lysogenic bacteriophage)
Signs and Symptoms: sore throat, fever, fatigue, malaise, swelling neck, pseudomembrane, heart/kidney failure, paralysis
Pathogenesis: potent diphtheria endotoxin
Spread by: humans, air and inhalation or from fomites
Treatment: antiserum, antibiotics, DTap vaccine

Question 3

Pneumococcal Pneumonia

Answer 3

Caused by: Streptococcus pneumoniae (gram+ diplococcus, polysaccharide capsule needed for virulence)
Signs and Symptoms: runny nose, congestion, temp rise, cough, fever, chest pain, sputum, rapid breathing (shallow)
Pathogenesis: capsule blocks phagocytosis, may enter bloodstream
Epidemiology: 30% of healthy people have pneumococci in throat

Question 4

Pertussis (Whooping Cough)

Answer 4

Caused by: Bordetella pertussis (encapsulated G- rod)
Signs and Symptoms: Catarrhal stage-inflammation of mucus membranes
paroxysmal stage-sudden attacks of coughing
convalescent stage-not contagious, coughing stops
Pathogenesis: inhaled, colonize nasopharynx, trachea, bronchi and bronchioles
Release 3 toxins, Pertussin toxin (increased mucus, decreased phagocyte killing), Adenylate cyclase (lyses leukocytes), Tracheal cytotoxin (release of fever-inducing interleukin-1)
Spread by: air droplets

Question 5

Influenza

Answer 5

Caused by: 3 major virus types
type A - most serious, orthomyxovirus family, enveloped segments of ssRNA (8 segments), hemagglutinin antigen (HA) and neuraminidase antigen (NA)
type B - less extensive, less severe
type C - minor
Signs and Symptoms: headache, fever, sore throat, muscle pain
Pathogenesis: inhalation of droplets or transfer to eyes, nose from fomites
Epidemiology: antigenic drift leads to seasonal influenza, allows for mixture of 8 RNA fragments