Transcript upper resp tract infection pper Respiratory Tract Infection

Upper Respiratory
Tract Infections
 Upper
R.T infections account for more visits to
physicians than any other diagnosis.
 In USA pharyngitis alone accounts for 40 million
physician visits annually.
 Respiratory tract infections include: rhinitis,
sinusitis, otitis media, pharyngitis, epiglottitis,
bronchitis, bronchiolitis and pneumonia.
 Pneumonia is the leading cause of death in children
worldwide. It kills children below five years old
more than AIDS, malaria and tuberculosis
combined.
Defense Mechanisms of Respiratory System
 The
defense begins in the nose, through specialized hairs
(vibrissae) that filter large particles from inhaled air.
 Epiglottis: protects airways from aspiration.
 Cough reflex.
 Mucociliary escalator.
 Alveolar macrophages (scavengers).
 Antimicrobial compounds: lysozyme, lactoferrin,
complement and IgA.
Microbial Ports of Entry:
 Direct
inhalation.
 Aspiration of upper airway contents. Spreading
along the mucous membrane surface.
 Hematogenous dissemination.
 Rarely: direct penetration.
Common cold
o Common cold (rhinitis) is a viral infection.
o Infection of the upper respiratory tract (nose,
o
o
o
nasopharynx and throat).
Preschool children are at greatest risk of frequent
colds. Children have an average of 8 colds per year,
adults 3 per year.
Most people recover from common cold within a
week or two.
Over 100 viruses can cause common cold.
Etiologies of Common Cold
 Rhinoviruses 30 to 35%.
 Influenza and adenovirus-30%.
 Coronaviruses about 10%.
 human respiratory syncytial virus (RSV) &Parainfluenza.
 Miscellaneous viruses.
Symptoms of common cold:
Sore throat, runny nose, nasal congestion, sneezing,
conjunctivitis (sometimes), myalgia, fatigue.
Complications:
Secondary bacterial infection (otitis media and sinusitis).
Acute Otitis Media & Sinusitis
Causes of Otitis Media:
Streptococcus pneumoniae (The most common bacterial
cause), Haemophilus influenzae (The second common
cause), S. pyogenes and Moraxella catarrhalis.
Causes of Sinusitis:
 Community acquired bacterial sinusitis:
S. pneumoniae, H. influenzae, S. pyogenes.
 Nosocomial sinusitis: in critically ill, mechanically
ventilated patients: S. aureus, Pseudomonas aeruginosa,
Serratia marcescens.
 Fungal sinusitis.
Throat Infection
(Pharyngitis)
 The
most common cause of pharyngitis in school-aged
children is group A Streptococci (S.pyogenes).
 The next most common causes of pharyngitis are:
• In Oropharynx:
o EBV, adenoviruses and enteroviruses: Coxsackievirus
group A causes herpangina (small vesicles on the mucus
membrane of throat) and hand, foot and mouth disease.
o Non-group A streptococci.
o Chlamydophila pneumoniae.
o Gonococcus.
o Meningococcus.
o Corynebacterium diphtheriae.
• In Nasopharynx (common cold):
o Rhinoviruses,
o Coronaviruses,
o Influenza virus.
 Although no
clinical features are diagnostic for specific
etiologic cause of pharyngitis but:
 Fever, tonsillar exudates, and tender cervical
adenopathy are usually associated with group A
streptococci Infection.
 Conjunctivitis, cough, coryza, and diarrhea are
usually associated with other causes.
Herpangina
Hand, foot and
mouth disease
S. pyogenes infection (Group A Streptococci):

Clinical presentations:
o Tonsillitis, pharyngitis, follicular tonsillitis, scarlet fever
and septic shock*.
o Toxigenic highly virulent strains of bacteria are
associated with establishment of septic shock and
scarlet fever ;(due to production of streptolysin-O,
streptolysin-S and exotoxin, and exotoxin A).
 Scarlet fever*:
Pharyngitis, fever, characteristic skin rash in the chest &
extremities and bright red tongue with "strawberry"
appearance.
Scarlet fever rash: diffuse erythema that blanches with pressure, with numerous small papules (sandpaper)

Infections by S. pyogenes can be complicated by:
• Peritonsillar abscess.
• Sinusitis.
• Otitis media.
• Rheumatic fever.
• Glomerulonephritis.
Peritonsillar abscess
Diagnosis of S. pyogenes:
 Clinical
specimens: throat swab, nasopharyngeal swab
and serum.
 Direct:
Culture on blood agar or chocolate agar: beta-hemolytic,
gram positive cocci in chains, capsulated and bacitracin
sensitive.
 Indirect: serology:
Anti streptolysin O titer (ASOT): significant titer is 200 IU
or more.
Beta hemolytic bacitracin sensitive colonies
B
Asymptomatic meningococcal pharyngitis
 Cause: Neisseria meningitides (gram –ve diplococci).
 Port of entry: inhalation of droplets from a carrier or a
patient in the early stage of disease.
 Primary infection:
Colonization of nasopharynx: asymptomatic
pharyngitis (carriers).
 Secondary: Meningococcemia , and meningitis.
 Diagnosis: CSF culture on chocolate agar with 10%
CO2.
Acute Epiglottitis: (Supraglottitis):
The most serious form of URTI.
 Most often in children 2 to 7 years of age.
 Most common cause in children is H. influenzae type b.
 Immunization of children (capsular Ag) reduced the
percentage of infection.
 Causes of epiglottitis in adults: Streptococcus pneumoniae,
Streptococcus pyogenes, H. influenzae.
 The infection results in rapid swelling of epiglottis and
cause these symptoms: fever, difficult breathing and
drooling of saliva.
 H. influenzae type b species can cross the mucosal barriers
causing meningitis, and septic arthritis.

Diagnosis of H. influenzae infections:
 In epiglottis infection:
Radiology and blood culture.
 In
•
•
Meningitis:
Clinical specimens: CSF, Blood.
Culture on chocolate agar at 10% CO2; because the
microbe is fastidious for factor X (hemin) and V.
(nicotinamide adenine dinucleotide).
Treatment of H. influenzae infection:
 Invasive infections: antibiotics e.g. third-generation
cephalosporin (ceftriaxone) should be started as soon
as appropriate specimens have been collected for
culture.
 Sinusitis, otitis media, and other upper RTI:
trimethoprim-sulfamethoxazole or amoxicillinclavulanate combination.
Croup: Infection of the Larynx (Laryngitis),
Trachea (Tracheitis) and bronchi (bronchitis):
 Almost all cases are caused by viruses esp.
Parainfluenza viruses 1-3. In rare cases:
Staphylococcus aureus.
 Children have smaller airways and nonexpendable
rings of trachea so edema is more likely to cause
narrowing of the lumen.
 Typically, mild upper R.T symptoms such as nasal
discharge and dry cough are present days before signs
of airway obstruction followed by sudden onset of
barking cough and difficult respiration.
 Treatment: It
is a self-limited infection resolve after 5 to
7 days. No specific antiviral drug. Corticosteroids and
inhaled aerosolized epinephrine can be used.
Laryngitis and Bronchitis:
 Laryngitis: in adults; the major clinical manifestation of
larynx infection is hoarseness.
 Acute tracheobronchitis:
Causes:
 Viruses: Rhinovirus, coronavirus, RSV, Influenzae virus.
 Bacteria: Chlamydophila pneumoniae, Mycoplasma
pneumoniae, and Bordetella pertussis (the causative
agent of whooping cough).
Whooping cough is a highly contagious fatal disease (outbreaks).
Pathogenesis and virulence of B. pertussis (Toxins):
 Pertussis toxin: inhibition of immune cells response.
 Adenylate cyclase toxin; increase cAMP production: affect
inflammation and increase edema.
 Tracheal cytotoxin: Nitric oxide production: kill tracheal
ciliated epithelial cells (paralyze the cilia and cause paroxysms
to remove the mucus).
Clinical presentation is characterized by two stages:
 Catarrhal stage:7-14 days; rhinorrhea, lacrimation, cough.
 Paroxysmal stage: (2 to 8 weeks): ten or more forceful coughs
followed by deep inspiration (whoop), cyanosis and vomiting.
A child with broken blood vessels in
eyes and bruising in face due to sever pertussis
 Immunization in
children (DTP) reduce Bordetella
pertussis infection*.
Diagnosis:
 Specimen: nasopharyngeal swab.
 The microbe can be isolated on charcoal cephalexin
blood agar as mercury drop colonies.
 Gram’s negative short, pleomorphic capsulated bacilli.