URTI Flashcards
Describe rhinovirus
Icosahedral, non-enveloped positive sense single-stranded linear RNA virus
What family does Rhinovirus belong to?
Picornavirus
Rhinovirus is the most common cause of what?
common cold (more common in fall and winter)
T or F. Rhinovirus is acid labile
T. Destroyed by stomach acid
How is rhinovirus transmitted?
person-to-person via respiratory droplets or indirectly by respiratory droplets on hands
Pathogenesis of rhinovirus
virus binds to ICAM-1 on respiratory epithelial cells and elicits inflammation to cause vasodilation, mucous secretion, and stimulation of sneeze and cough reflexes
What is the incubation period of rhinovirus?
2-4 days (illness lasts about 1 week)
Treatment of rhinovirus?
Supportive only
Describe coronavirus
Helical, enveloped, + sense single-stranded linear RNA that accounts for 15-20% of URTIs
active in winter in a 2-3 yr cycle
T or F. Coronavirus does NOT cause LRTIs
T. except SARS and MERS
What else can coronavirus cause?
GI illness
Describe Bordetella pertussis
small coccobacillary, encapsulated gram negative rod
What disease does Bordetella pertussis cause?
Whooping Cough
What major toxin does Bordetella pertussis use?
A-B toxin
What does A-B toxin do?
stimulates adenylate cyclase by catalyzing the addition of ADP-ribosylation to the inhibitory subunit of the G protein complex, resulting in overactive cAMP- dependent protein kinase activity which impairs phagocytosis
How is Bordetella pertussis transmitted?
airborne droplets (very contagious)
What are the stages of Bordetella pertussis infection?
- catarrhal (2 wks of mild URT symptoms)
- paroxysmal (2-3 months of severe cough)
- Convalescent (1-2 wks of cough reducing)
How is Bordetella pertussis diagnosed?
- Nasopharyngeal swab (PCR)
- Culture
- CBC With LYMPHOCYTOSIS
Why is lymphocytosis seen Bordetella pertussis?
pertussis toxin inhibits signal transduction by chemokine receptors, resulting in failure of lymphocytes to enter lymphoid tissue such as spleen and lymph nodes
How is Bordetella pertussis treated?
-Azithro for all regardless of age or symptom presentation (if given very early it can shorter course duration but if given later the toxin has probably already damaged the respiratory mucosa BUT will reduce risk of complications such as PNA or respiratory failure)
Describe Corynebacterium diphtheriae
gram + pleomorphic bacillus, club shaped
Pathogenesis of Corynebacterium diphtheriae
A-B toxin blocks protein synthesis by inactivating elongation factor 2 (EF-2) by ADP ribosylation AND
can induce formation of a pseudomembrane
How does Diphtheria present?
gradual onset of:
- sore throat
- malaise/fatigue/fever
- cervical LAD (‘bull neck’)
- neuropathies
How does Diphtheria affect the heart?
myocarditis 7-14 days after onset of respiratory symptoms
What is a pseudomembrane?
membrane composed of necrotic fibrin, leukocytes, RBCs, epithelial cells, and organisms that adheres tightly to underlying tissue and bleeds with scraping
How is Diphtheria diagnosed?
- Throat swab culture of Loeffler’s medium, tellurite plate
- Methylene blue plate good for revealing metachromatic granules
What color tellurite plate is positive?
gray-black
How is Diphtheria treated?
Antitoxin administration AND either penicillin or erythromycin. Treat immediately!!
What are the most common causes of acute otitis media?
Strep pneumo, H. influenzae, or Moraxella catarrhalis
Treatment for acute otitis media?
Amoxicillin or
Augmentin for those who have had recent ABX or have a history of AOM unresponsive to amoxicillin (give if you see purulent conjunctivitis)
Treatment of acute sinusitis?
Augmentin (if they get better or get worse)
What is epiglottitis?
inflammation of the supraglottic region of the oropharynx with inflammation of the epiglottis, vallecula, and arytenoids
Major causes of epiglottis?
- H. influenza
- H. parainfluenzae
- GAS
- Strep pneum
Typical patient population for epiglottitis?
urban male in 40s
How does epiglottitis present? Treatment?
sore throat, dysphagia, muffled voice
treat with ceftriaxone because severe
prognosis good normally
What factors does H. flu require for growth?
V and X (grows on chocolate age)
Strep pneumo is becoming more resistant to penicillin. How?
altered penicillin binding proteins
Why is altered penicillin binding proteins the more likely cause of resistance in gram + and B-lactamases more likely in gram negatives?
Gram negatives can secrete the lactamases into the peri-nuclear space and it is more concentrated
Why is otitis media more common in children?
Eustachian tubes are shorter, narrower, and more horizontal than in adults.
Rhinovirus grows better at lower temperatures. There is evidence that rhinovirus can contribute to pneumonia.
Rhinovirus grows better at lower temperatures. There is evidence that rhinovirus can contribute to pneumonia.
What is a gram+, forming long branching filaments, anaerobics; associated with “sulfur granules”?
Actinomyces
What should be done if C. diphtheria is recovered from culture?
either Ab inoculation or antibody-based gel diffusion precipitin test is performed to document toxin production. or PCR for presence of toxin gene
Vaccine schedule for Dtap?
2,4,6; 15-18 months and kindergarten; booster at 11 and in between 19-64 yoa
An x-ray of epiglottis would show what?
thumb sign showing inflammation
