Upper respiratory tract infections                          Reading: pg. 201 – 216

• Normal flora (fig. 18.1, pg. 201)
• Anatomy of the respiratory tract (fig. 18.2, pg. 202)
• Types of respiratory infection (fig. 18.3, pg. 202)
• Respiratory invaders (fig. 18.4, pg. 203)
• Common cold (fig. 18.5, pg. 205, fig. 18.6, pg. 206)
• Pharyngitis and tonsillitis (fig. 18.7, pg. 207
  • CMV (fig. 18.11, pg. 208)
  • EBV (fig. 18.12, pg. 209)
  • Bacterial
• Parotitis
• Otitis and sinusitis
  • Acute otitis media
  • Otitis externa
  • Acute sinusitis
• Acute epiglottitis
• Oral cavity infections
• Laryngitis and tracheitis

Upper respiratory tract infections

Normal flora

n   Harmless

n   May cause problems when host resistance is low.

n   Defenses:

n   Mucociliary system

n   Saliva – flushing action

The upper and lower respiratory tracts form a continuum for infectious agents

n  coronaviruses, rhinoviruses

n  perfer nasopharynx

n  Parainfluenza viruses

n   Nasopharynx – cold

n   Larynx and trachea

n   Croup or laryngotracheitis - inflammation and narrowing of larynx and trachea (windpipe)

n   Bronchi and bronchioles

n   Bronchitis

n   Bronchiolitis

n   Pneumonia

Anatomy of the upper respiratory tract

Generalizations about upper and lower respiratory tract infections

n        Microbes

n        may be restricted to surface epithelium

n        spread to other parts of the body

Types of respiratory infection

•                 Two groups of respiratory invaders

Common cold

n   Common cause are viruses

n   50% of colds caused by coronaviruses and rhinoviruses; other viruses are coxsackie virus A and echovirus

n   Fig. 18.5 Viruses possess different attachment mechanisms that allow them to:

n   bind tightly to host cells

n   infect host cells

n   spread to neighboring cells

n   Cause damage to epithelial cells

n    fluid from the nose are filled with viruses – sneezing discharges viruses into air

n    Transmission – aerosol and contaminated hands

n    Diagnosis:

n    clinical appearance - Sneezing, scratchy throat, runny nose, headache, coughing

n    viruses rarely cultured – pandemic strains of influenza

n    Molecular techniques - detect and identify these strains

n    Treatment is symptomatic

n    Decongestants, analgesics, cough medicine

Pharyngitis and tonsillitis

n   Pharyngitis

n   sore throat, inflammation of pharynx

n   Tonsillitis

n   infection and inflammation of tonsils

n   70% of sore throats are caused by viruses

CMV

n  largest human herpesvirus

n  Multiply in pharynx

n  Spreads to lymphoid tissues

n  systematically in circulating cells

EBV

n   Species specific, humans are natural host

n   Herpesvirus with unique viral capsid antigen (VCA) – used for diagnostic tests

n   Transmitted by saliva – kissing (infectious mononucleosis)

n   Clinical features are immunologically mediated

n   Fig. 18.12

n    associated with several cancers:

n   Burkitt’s lymphoma – African children, malaria is cocarciogen

n   Other B lymphomas in immunodeficient patients

n   Nasopharyngeal carcinoma – Asia, nitrosamines are cocarcinogen, from preserved fish

n   evades host defenses by:

n   Producing fake IL-10 (an immunoregulatory cytokine)

n   Preventing apoptosis of infected cells

n   Integrating into genome of or episomal form in B cells

n   immunodeficiency leads to reactivation of virus

n   Treatment:

n   No vaccine

n   No antiviral agent, acyclovir seems effective in vitro

Bacteria responsible for pharyngitis

• S. pyogenes

n    Complications with Strep throat:

n   Peritonsillar abscess (quinsy)

n   Otitis media, sinusitis

n   Scarlet fever (S. pyogenes production of erythrogenic toxin)

n   Rheumatic fever

n   Rheumatic heart disease

n   Acute glomerulonephritis

n    Diagnosis

n    Use of antibodies specific for each virus

n    Bacteria – throat swab and bacterial culture

Parotitis

n    Mumps virus – ssRNA paramyxovirus

n   Spread: droplets, saliva, urine (close contact necessary)

n   Signs: painful, swollen parotid glands

n    Fig. 18.17: incubation 18-21 days

n    No treatment

n    Prevention: MMR vaccine

Otitis and sinusitis

n   Cause:

n   viruses (mumps virus, respiratory syncytial virus (RSV))

n   Bacteria

n   If untreated – may lead to:

n   Deafness

n   blockage of eustachian tube and opening of sinuses

Otitis and sinusitis

n    Acute otitis media (infection of inner ear)

n    causes: viruses, S. pneumoniae, H. influenzae

n    Common in infants and small children

n    Signs: dilated vessels, fluids in ear drum

n    Chronic ear infections à impaired hearing and learning difficulties

n    Otitis externa (infection of outer ear)

n    Causes: S. aureus, C. albicans and Gram – opportunistic pathogens (Proteus and P. aeruginosa)

n    Acute sinusitis (sinus infection)

n    Causes: same as infection of the inner ear

n    Signs: facial pain and tenderness

Acute epiglottitis

n   Infection, inflammation and edema of epiglottis

n   Cause: H. influenzae capsular type B

n   Usually an emergency situation – bacteremia

n   Difficulty breathing

n   Requires intubation to secure airway and immediate antibiotic treatment

n   Hib vaccine can reduce infections

Oral cavity infections

n    Oral candidiasis – thrush

n   Infection by C. albicans due loss of normal oral flora due to antibiotic treatment, impaired immunity, or vitamin C deficiency

n    Caries

n   S. mutans – break down sugars to form acids that destroys enamel à caries (cavities) à spread to pulp à root abscess

n    Periodontal disease:

n   Infection of crevice between teeth and gum by bacteria (Actinomycetes viscosus, Actinobacillus and Bacteroides spp)

n   Gum recedes leading to tooth lost

Laryngitis and tracheitis

n   Causes: parainfluenza virus, RSV, influenza virus or adenovirus

n   Signs: hoarseness, coughing (croup)