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What is the infection?

  • A 12 month-old male child, Darren, is off form for 24-36 hours and is noticed by his parents to be hot and irritable. The illness fails to settle with paracetamol and he is brought to his GP for assessment.
  • Examination reveals a bulging, opaque eardrum.

Burden of RTI

  • Up to 1⁄2 of all symptomatic illness
  • Significant morbidity and direct health care costs
  • Occasionally leads to fatal illness

The defense mechanisms of the respiratory tract

NB: In the lower RT, it is almost completely sterile (due to defence mechanisms - mucociliary mechanism and alveolar macrophages). However in the URTI, the mucosa is colonised by normal flora

Common Residents (>50% of normal people)

  • Streptococcus spp.
  • Corynebacterium spp.
  • Neisseria spp.
  • Anaerobic cocci
  • Haemophilus influenzae *
  • Staphylococcus aureus *
  • Candida albicans

The Common Cold

  • Infection of the Nasopharynx (specifically the nose-epithelial cell layer)
  • ~ 8 episodes per year
  • Diagnosis by clinical appearance
  • Acute rhinorrhea
  • Sneezing
  • sore throat
  • Cough
  • Malaise
  • headache
  • Fever may be present
  • Aetiological agents
    • Rhinoviruses (>100 serotypes)
    • Coronaviruses
    • Parainfluenza viruses
    • Respiratory syncytial virus
    • Unknown causative organisms
  • Treatment is symptomatic
    • No vaccines yet for common cold
  • Complications:
    • Otitis media
    • Bacterial pharyngitis
    • Pneumonia

Influenza

  • Influenza virus, 3 types:
    • A:
      • Further subtyped eg H5N1
      • Epidemic and pandemic
      • Moderate to severe
    • B:
      • Epidemics
      • Moderate
    • C: mild
  • Complications
    • Secondary bacterial infection
    • Pneumonia is the most common

Pharyngitis and tonsillitis

  • What are they?
    • Inflammation of the pharynx (pharyngeal tonsillitis)
    • Inflammation of the tonsils
    • Often coexist
  • Essentials of diagnosis
    • Sore throat
    • Pain when swallowing
    • Fever
    • Enlarged lymph nodes
    • Runny nose and postnasal drip
    • Headache
    • In rare cases, difficulty breathing
    • Pharyngeal erythema with or without exudate (exudate with pus --> bacterial)
  • Aetiology
    • Viruses (80%)
    • S. pyogenes (10%-20%)
    • Epstein-Barr virus (<5%) (not common in young children, differential Dx in older children)
      • infectious mononucleosis or Glandular Fever
  • Laboratory diagnosis
    • Microscopy of throat swab uninformative (commensal organisms always present)
    • Rapid strep antigen test → detects GAS antigen
    • Throat culture → “gold standard”
      • >95% sensitivity
    • Serologic test for EBV (older children)
  • Streptococcus pyogenes
    • GP cocci
    • Most acute bacterial pharyngitis
    • Direct/Suppurative complications (localised)
      • Peritonsillar abscess formation
      • Otitis media, Sinusitis
    • Indirect or Non-suppurative complications (due to antibody formation)
      • Rheumatic Fever
      • Acute glomerulonephritis

Important to use antibiotics in people who have had rheumatic fever to prevent a second episode of rheumatic fever

  • When to treat
    • Severe tonsillitis with clinical features suggestive of bacterial aetiology (acute onset, anorexia, fever)
    • Patients in population groups with high incidence of acute RF eg Central and Northern Aust. aboriginal communities

Otitis media

If the mucociliary epithelium in the Eustachian tube is undamaged, then infectious material is drained away from the ear down to the nasal cavity. If damaged, infection can occur in the middle ear.

  • Acute OM
    • Fever and pain
    • Effusion
  • OM with effusion
    • glue ear (fluid in middle ear)
    • Absence of fever or inflammation
  • Recurrent OM
    • >3 episodes in 6 months
  • Chronic OM
    • persistent infection, some patients don't even realise, not seeking treatment. In children, this has consequences in terms of learning and development
  • How common is AOM?
    • 83% child at least 1 episode by age of 3
    • Peak at 6 to 12 months
    • More common among Aboriginal, Torres Strait Islanders or from a non-English background
  • Why is AOM common in younger children?
    • The Eustachian tube is shorter, more horizontal, and straighter
    • Medial orifice is more open
    • Young children get more viral respiratory infections
    • Supine feeding
  • What is the infection?
    • A 12 month-old male child, Darren, is off form for 24-36 hours and is noticed by his parents to be hot and irritable. The illness fails to settle with paracetamol and he is brought to his GP for assessment.
    • Examination reveals a bulging, opaque eardrum.
  • Aetiology
    • 50% viral
    • Other 50% are bacterial, shown below
      • Streptococcus pnemoniae
        • Alpha Haemolytic
        • Sensitive to Optochin
        • Gram positive diplococci
      • Haemophilus influenzae
        • Culture on chocolate blood agar
        • Gram negative rod
        • Two types:
        1. Encapsulated
          • Serotypes a-f (Type B most virulent)
          • Nasopharyngeal carriage (5-10%);
        2. Non-encapsulated
          • Nasopharyngeal carriage (25-80%)
    • Microbiological investigation
      • Tympanocentesis culture
      • Routine culture not recommended (carries risks)
  • AOM treatment
    • Systemic signs (vomiting and fever)
      • Antibiotics
    • Otherwise:
      • Symptomatic treatment
      • Wait and see
        • < 2yr: 24 hrs
        • >2 yrs: 48 hrs
        • Re-evaluate and antibiotics
  • Sequelae (is a pathological condition resulting from a disease, injury, or other trauma)
    • Temporary hearing loss - not a problem
    • Permanent hearing loss
    • Problems with speech and language development

Sinusitis

  • Inflammation/Infection of one or more paranasal sinuses →
    • can be acute, chronic, or recurrent
  • Symptoms
    • Purulent rhinorrhea and nasal congestion
    • Fever and facial pain
  • Aetiology
    • Pathogens = Same as for AOM
      • S. pneumoniae
      • M. catarrhalis
      • Non-typable H. influenzae

Acute laryngitis

  • Inflammation of the larynx
    • History
      • sore throat
      • dysphonia (hoarseness) or loss of voice
      • Cough
      • possible low-grade fever
    • Physical Exam
      • cannot directly visualize larynx on standard PE
    • Associated symptoms of rhinitis, pharyngitis or cough
    • Mostly viral, occasionally bacterial

Acute laryngo-tracheo-bronchitis (Croup)

  • Fever
  • hoarseness of voice
  • No productive cough
  • Characteristic inspiratory stridor (not wheezing)
  • Mostly viral
    • Parainfluenza virus types 1 and 2
    • Influenza A or B
    • RSV

Diphtheria

  • What is it?
    • an acute bacterial disease
    • affects the tonsils, throat, nose and/or skin
  • Causative organisms:
    • Corynebacterium diphtheriae
  • Respiratory form (due to production of toxin)
    • Pharyngitis
    • Obstruction (inflamed air passage)
    • Toxic myocarditis
    • Congestive heart failure (toxin mediated myocarditis)
  • Transmitted by respiratory droplets
  • Vaccination prevents this

Acute epiglottitis

  • Often young children
  • Severe inflammation and oedema - can be an emergency in small children (no physical examination of the epiglottis unless you have intubation facilities, because you don't want suffocation to happen)
  • Haemophilus influenzae
  • Recent rapid decline in incidence (recent H. influenzae serotype B vaccination)

Whooping Cough (Pertussis)

Causes both URTI and LRTI

  • An acute bacterial infection of the respiratory tract
  • Vaccine preventable disease
  • Disease is most severe in young children
  • Characterised by one or more:
    • Paroxysms of coughing
    • Inspiratory whoop without other apparent cause (cough then gasp for air)
    • Post-tussive vomiting
    • Persistent cough lasting > 2 weeks
  • Pathogenesis and clinical features
    • Three stages of illness:
      • Catarrhal (coughing) 1 – 2 weeks
      • Paroxysmal 1 – 6 weeks
      • Convalescence (coughing with no organism) Can last for months
    • Disease is often milder in adolescents and adults
    • Older groups often transmit the organism to vulnerable children
  • Complications in infants and children
    • Pneumonia
    • Neurologic complications (hypoxia, and also toxin, cause this)
    • Bordatella pertussis
  • Causative Agent
    • Bordetella pertussis
      • GN bacteria
      • Small
      • Strictly aerobic
      • Cocobacillus
  • Diagnosis
    • Diagnosis difficult in catarrhal stage
    • Isolated in only 30-50% of cases
      • organism fragile and fastidious
      • nasopharyngeal swab or aspirate for children (only 50% sensitive)
      • 2-3 days culture required
      • Throat swab not suitable for culture (but good enough for PCR)
    • Alternative diagnostic method
      • Serology (IgA in blood)
      • PCR (throat swab)
  • Treatment
    • Early antibiotic treatment may be beneficial
    • Antibiotic therapy may limit spread of organisms (major benefit of antibiotic)
      • Also good for prophylaxis of exposed individuals
    • Drugs may aim at symptoms
      • anti-tussives
      • anti-spasmotics
      • Sedatives
    • Notifiable disease
    • Antibiotic prophylaxis
    • Check immunisation of children in the same household