49. Upper Respiratory Tract Infections Flashcards
What comprises the URT?
What are some common and important URT infections?
List some common viral respiratory pathogens.
Nose, paranasal sinuses, middle ear, nasopharynx, oropharynx, laryngopharynx, tonsils and adenoids. NB: whole URT colonised by dynamic variety of normal flora.
Common: Colds, pharyngitis (sore throat), laryngitis, tonsilitis, sinusitis, otitis media (middle ear infection) *MOST CAUSED BY VIRUSES and self limiting*
Important: group A strep infection (severe sore throat, quinsy, rheumatic fever, glomerulonephritis), epiglottis - Haemophilus influezae type B -> asphyxiation!
Adenovirus, parainfluenza virus, respiratory syncytial virus, rhinovirus
What are some general characteristics of URTIs?
What are some symptoms of URTIs?
What are colds?
Why is it hard to make a cold vaccine?
Severity varies (more severe at age extremities), morbidity direct/indirect, slow detection of viral pathogens by PCR/culture/serology, rapid diagnostic tests for influenza and RSV
Onset 1-3d, duration 7-10d, acute pharyngitis may be caused by strep A bacteria = sore throat is 1st symptom.
Usually caused by many strains of rhinoviruses (50% of colds, over 100 serotypes!) and sometimes coronaviruses/other. Main feature = watery to mucoid/purulent nasal discharge - coryza. Often preced by a sore throat, sometimes with fever. Can cause otitis media in kids/sinusitis in adults.
So many different serotypes
What is pharyngitis?
How is it diagnosed?
How is it treated?
What are the complications?
How is it prevented?
Caused by group A strep, sore throat, fever, +/- tonsiliar exudate, tender cervical nodes, may lead to quinsy and occasionally scarlet fever.
Bacterial culture of throat swab (e.g. G+ cocci in chains), serology (ASOT, anti-DNase B)
Antibiotics (all penicillin sensitive and most erythromycin sensitive)
Rheumatic fever -> damage to heart valves etc., glomerulonephritis
Isolate hospiral cases, ensure sufficient treatment, consider carrier recognition
What causes otitis media?
How is it treated?
Viruses, Bacteria: Streptococcus pneumoniae/pyrogenes, Haemophilus influenza, S. aures, Mycoplasma pneumonae, Chlamydia pneumonniae, Moxella catarrhalis
Childen: treatment generally symptomatic, antibiotics not given initially. Less common in adults, not normally given antibiotics.
What causes sinusitis?
How is it treated?
Viral (as for other URTIs), Bacterial: overgrowth of ‘normal’ flora incl Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis
Not always necessary. Consider co-amoxiclav, clarithromycin
What are the clinical features of epiglottitis?
What might CT/ lateral X-ray show?
Is it a medical emergency? Why?
Rapid onset fever, sore throat, dysphagia, may lead to respiratory obstruction. Almost always due to bacteria.
Swelling of soft tissues of neck.
Yes - can swell and obstruct trachea. Need airway intubation/tracheostomy, antibiotics (cefotaxime, ceftriaxone), prophylaxis for unimmunised household contacts. V. rare now. Normally caused by Haemophilus influenzae.
What is whooping cough caused by?
What happens in the disease and what are the signs/symptoms?
How is it diagnosed?
What is the treatment?
How can it be prevented?
Caused by Bordetella pertussis, toxin mediated disease
Week 1: catarrhal phase = cough increases, 2 weeks: worse cough, whoop (vigerous inspiration through glottis at end of paroxysm), vomit, subconjunctival, cerebral and nasal hemorrhages.
Pernasal swab, innoculated immediately, special medium, slow growing (5 days), direct immunofluorescence.
Erythromycin in catarrhal stage = decrease transmission
Acellular vaccines contains various virulence factors (filamentous hemagglutinin, agglutinogens, outer membrane protein) and inactive form of pertussis toxin. WENT AWAY BUT NOW COMING BACK ABIT B/C SOME WERE NOT IMMUNISED.
What causes diptheria, and what happens?
What stain can be used for it?
How do you detect toxin production?
How is it treated and prevented?
Corynebacterium diphtheriae (G+ rod), severe pharyngitis, see pseudomembrane covering posterior pharynx. Diptheria toxin stops protein synthesis by blocking transcription - toxin absorbed and die of heart attack b/c stops protein synthesis in heart.
Chinese characters Alberts stain
Eleck’s Test - only C. diphtheriae that have been infected with a particualar bacteriophage produce the toxin.
(Based on clinical diagnosis while awaiting microbiology) Isolate, anti-toxin, penicillin, monitor for respiratory obstruction. Prevented by immunization (childhood DTP). Also prophylaxis + erythromycin for contacts.
What does Epstein Barr Virus cause?
How is it diagnosed?
How is it managed?
Infectious mononucleosis (glandular fever), systemic disease, usually presents as sore throat. Exudates on tonsils and pharyngeal swelling. Enlargement of spleen and liver.
Clinical WWC, monospot test, IgM Abs against EBV
Rest, analgesia, hospital if respiratory obstruction -> may need steroids. If antibiotics needed for 20 bacterial respiratory infection DO NOT GIVE AMPICILLIN - this will cause rash.
What is this condition?
Pseudomembrane - diptheria
How is adenovirus spread, and what does it infect?
What syndromes can it cause?
Droplet, formites and ingestion. Infect mucous membranes of eye, respiratory and GI tract, occasionally urinary. Local lymph nodes often involved. Infections usually self-limiting.
Epidemic kerato-conjunctivitis (cornea infection), Pneumonia (if follows measles), Acute respiratory disease
What is RSV?
What can it cause?
What are paramyxoviruses?
What are the types?
Respiratory syncytial virus, single major pathogen in UK childhood infections. Causes fairly localised infection of respiratory tract.
Bronchiolitis, laryngotracheobronchitis, pneumnia, bronchitis.
Similar to influenza, spherical, spiky envelope, haemagglutinin and neuraminidase (cell attachment/release of new virion progeny proteins)
1-4. More severe LRTI associated with T1-3. Type 1 associated with LTB.
What is another name for croup, what is it caused by, and when does it manifest?
What are the signs/symptoms?
How is it diagnosed?
How is it treated?
Acute laryngotracheobronchitis, caused by viruses (RSV, parainfluenza 1-3), occurs 3m - 3yrs.
Hoarseness, cough ‘seal’s bark’, stridor
Nasopharyngeal aspirate for immunofluorescence/PCR -> ID virus type
Monitor for respiratory obstruction, humidify inspired air, consider ribavirin only for v. sick kids (antiretroviral)
How does influenza enter the body?
Describe the viral replication process.
What is an idea target for influenza antiviral intervention?
Where does influenza act in the body?
Enters through the nose and settles in the respiratory tract.
Binds to cell surface (via haemagglutinin), enters cell, viral genome released into cell nucleus for replication, viral proteins produced allowing assembley of progeny virus particles to be formed and released (via neuraminidase).
Surface: Active site of influenza neuraminidase always highly conserved as it’s essential for replication = target!
URTI by one of the influenza virus pathogens (Type A, B or C). Annual epidemic strains affect URT and sometimes track down and cause LRTI. Cells influenza binds to have sialic acid residues on surface.
What are the pandemic influenzas of the 20th century?
How is influenza prevented?
What animal spp harbour influenza A viri?
H1N1, H2N2, H3N2. Waves typically last 6 - 8w.
Flu vaccine against common strains, given to high risk people e.g. hospital staff, the very young/old, comorbidites. Can use neuraminidase inhibitors: zanamavir/oseltamavir to treat AND prevent.
Shorebirds, waterfowl, domestic birds, mammals e.g. pigs. All have their own flu. Worry that birds can pass to pigs -> to us (zoonosis!)
