URTIs

Question 1

Rhinovirus
• Stucture
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 1

Stucture
Picornavirus family: Icsoahedral, NON-enveloped, positive-sense, single-stranded linear RNA virus

Transmission
Respiratory droplets or indirectly by transfer of droplets from fingers to nose or mouth

Replication Cycle
Not Mentioned

Disease Presentation
Typically you get sick 2-4 days later with URTI symptoms only, NO SYSTEMIC SYMPTOMS other than mild chills

Pathogenic Mechanism
Virus binds ICAM-1 allowing it to adhere to respiratory epithelial cells. Presence of virus causes bradykinin and PGs to be released leading to cold symptoms

Epidemiology
60% of URTIs typically causes disease in the Fall and Winter

Treatment
Supportive only

Key findings/Diagnosis
absence of systemic symptoms is important
Dx: Clinical

Question 2

Coronavirus
• Stucture
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 2

Stucture
Helical enveloped, single stranded positive sense linear RNA

Transmission
Not mentioned

Replication Cycle
Not mentioned

Disease Presentation
Only LRTIs are MERS and SARS. Unlike rhinovirus it has the potential to cause GI illness

Pathogenic Mechanism
not mentioned

Epidemiology
Account for 15-20% of all URTIs, WINTER outbreaks occur in 2-3 year cycles

Treatment
Mortality
Key findings/Diagnosis

Question 3

Bordetella pertussis
• Stucture
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 3

Stucture
Encapsulated, small Coccobacillary gram-negative Rod

Transmission
HIGHLY contageous and transmitted via airborne droplets

Replication Cycle
Not mentioned

Disease Presentation
3 important stages of infection:
1) Catarrhal: 2 weeks of mild URT symtoms
2) Paroxysmal: 2-3 months or severe - WHOOPING Cough in children, unlikely to be as severe in adults.
3) Convalescent: 1-2 weeks of reduction in cough

Pathogenic Mechanism
A-B toxin (pertussis toxin) - B part of the toxin gains entry to host cell and allows A portion to catalyze the ADP-ribosylation of inhibitory unit of the G protein complex this results in overactive Andenylate Cyclase and AMP-dependent protein kinase activity => IMPAIRS PHAGOCYTOSIS and REDUCES CILIARY ACTIVITY.
***This toxin also impairs chemokine receptors and blinds lymphocytes from lymph tissue and you get a LYMPHOCYTOSIS.

Epidemiology
People who haven’t been vaccinated

Treatment
Azithromycin with positive labs regardless of age or symptoms or with clinical dx. treat all pts. who have had less than 21 days of symptoms (treat after longer times if risk of contacting high risk person)

Vaccination: DTap (2,4,6, 15-18, 4-6mo., 11yrs) and tdap (19-64 yrs)

Mortality
Not Mentioned

Key findings/Diagnosis
keys: CBC with STRIKING LYMPHOCYTOSIS
Dx: Nasopharyngeal Swab (DFA or PCR) and Culture

Question 4

Corynebacterium diptheriae
• Stucture
• Transmission
• Replication Cycle
• Disease Presentation
• Pathogenic Mechanism
• Epidemiology
• Treatment
• Mortality
• Key findings/Diagnosis

Answer 4

Stucture
Gram positive bacillus, pleomorphic, club-shaped, Palisading, beaded appearance

Transmission
Not mentioned

Replication Cycle
Not mentioned

Disease Presentation
Gradual onset of sore throat, malaise, low-grade fever, BULL NECK (cervical lymphadenopathy), MYOCARDITIS, Neurologic Toxicities (especially with cranial nn.), Mechanical Obstruction

Pathogenic Mechanism
A-B toxin blocks protein synthesis by inactivating elongation factor 2 (EF-2) by ADP ribosylation, resulting in decreased protein synthesis. (note: pseudomonas has a similar exotoxin) - this toxin cause PSEUDOMEMBRANE formation

Epidemiology
Not mentioned

Treatment

• *Vaccinate**: DTaP, tdap
• *TREAT IMMEDIATELY**, don’t wait on Dx. ANTITOXIN + penicillin or erythromycin

Mortality
Not Mentioned

Key findings/Diagnosis
Pseudomembrane of necrotic tissue that bleeds with scraping

• *Dx:
  1. Throat swab and culture onLoeffler’s medium, tellurite plate, AND blood agar.**
  2. Isolate C. diptheriae and document toxin production
  3. Metachromatic granulesshould be visualize on throat swab withmethylene blue dye (reveals METACHROMATIC granules)

**Remember bacterial colonies turning tellurite black is diagnostic**