RESP TRACT INFECTIONS

Question 1

How is the respiratory tract divided?

Answer 1

Anatomically, respiratory tract is divided into upper (organs outside
thorax -nose, pharynx and larynx) and lower respiratory tract (organ
within thorax -trachea, bronchi, bronchioles, alveolar duct and
alveoli).

Question 2

What’s the main function of the respiratory system?

Answer 2

Filter
Warm
Humidify AIR

Question 3

Main function of lower RTI

Answer 3

Provide gas exchange for O2 and CO2

Question 4

What are the natural antimicrobial defences of the tract?

Answer 4

Microbes constantly enter airways but many factors
prevent colonisation:
* Mucociliary system
* Nasal vibrissae
* Action of cilia
* Mucous glands and goblet cells
The movements of the cilia push anything in it such as
inhaled particles or microorganisms up and out into the
throat, which can either get swallowed or removed
through the mouth.

Bronchoconstriction
* Cough reflex
* Intact epithelial barrier
* Secreted factors such as:
 Secretory antibody IgA
 Surfactant proteins
* Alveolar macrophage system
* Local cell cell-mediated immunity

Question 5

What happens if you disrupt or overwhelm the defence systems?

Answer 5

Allows microbes to colonise RT

Question 6

What factors favour colonisation

Answer 6

Disruption of mucociliary clearance:
Disruption of intact epithelial barrier:
Increasing “inoculation” events:
Decreasing immune function:

Question 7

How does disruption of mucocilliary clearance colonise

Answer 7

airway obstruction (i.e. CF , chronic bronchitis)
* ciliary dysfunction (i.e. smoking)

Question 8

How does Disruption of intact epithelial barrier: colonise?

Answer 8

injury(e.g. pulmonary oedema , intubation) or infectioninfection(e.g. viral respiratory infection such as influenza)

Question 9

how does Increasing “inoculation” events: colonise?

Answer 9

altered consciousness
* debility
* dysphagia
* intubation
* bacteraemia§

Question 10

How does Decreasing immune function: colonise?

Answer 10

immune suppression (transplant, HIV HIV

Question 11

Where do URTI occur?

Answer 11

Upper respiratory tract infections occur in the upper respiratory system: nose, nasal
cavity, mouth, throat or pharynx, and larynx above the vocal folds.

Question 12

How severe is URTI?

Answer 12

The spectrum of severity ranges from self self-limiting viral infections that resolve without
medical consultation to life threatening systemic bacterial illness.E

Question 13

Examples of URTI?

Answer 13

Examples of upper respiratory tract infections include the common cold cold, pharyngitispharyngitis, epiglottitis , and laryngotracheitislaryngotracheitis.

Question 14

Common cold syndrome

Answer 14

An acute, self self-limiting syndrome comprising clear nasal discharge, accompanied by other
upper respiratory tract symptoms.

Question 15

What causes common cold?

Answer 15

Rhinoviruses with more than 100 serotypes are the most common pathogens, causing at
least 25% of colds in adults.
* Coronaviruses may be responsible for more than 10% of cases. Parainfluenza viruses,
adenoviruses and influenza viruses have all been linked to the common cold syndrome.
* Bacterial pathogens are less common than viral but can include Streptococcus pneumoniae,
Mycoplasma pneumoniae, Haemophilus influenzae.
* Bacterial sinusitis, bronchitis, or pneumonia may also occur secondarily after a viral
respiratory infection.

Question 16

Common cold symptoms

Answer 16

SymptomsSymptoms:
 Sneezing
 Nasal obstruction and discharge
 Sore throat
 Headache
 Mild cough
 Malaise
 Chilly sensation
 Fever.
 Secondary bacterial infection may lead to otitis media, sinusitis, bronchitis or pneumonia.
Maliase
Headache

Question 17

Pathogenesis of the common cold

Answer 17

Direct invasion of epithelial cells of the respiratory mucosa.
 An increase in both Immune cells infiltration and nasal secretions, suggesting that cytokines
and immune mechanisms may be responsible for some of the symptoms.

Question 18

Diagnosis of common cold

Answer 18

Usually based on symptoms.
 Although it is possible to isolate the viruses for definitive diagnosis, that is rarely warranted.

PCR?

Question 19

In depth pathogenesis of common cold

Answer 19

Infection
Virus Absorbed
Virus Replicates
Clear fluid produced from lamina proper
Cell damage
Infection spreads
Host defences activates WBC
Recovery with interferon and antibody production

Question 20

What is sinusitis?

Answer 20

Inflammation of the nose and the paranasal sinuses.
* Sinusitis often results from infections of other sites of the respiratory tract since the
paranasal sinuses are continuous to, and communicate with, the upper respiratory tract.

Question 21

Symptoms of Sinusitis

Answer 21

Characterised by two or more symptoms, one of which should be either nasal
blockage/obstruction/congestion or nasal discharge (anterior/posterior nasal drip).
* Allergic rhinitis may also be antecedent to the development of sinusitis.
* Infection of the maxillary sinuses may follow dental extractions or infection.

Question 22

Viruses of Sinusitis

Answer 22

Streptococcus pneumoniae pneumoniae, Haemophilus influenzae influenzae, Staphylococcus aureus aureus, Streptococcus
pyogenes.

Question 23

Symptoms of Sinusitis

Answer 23

 Facial pain/pressure
 Reduction or loss of smell
 Malaise
 Low grade fever may also occur

Question 24

Pathogenesis of Sinusitis

Answer 24

Pathogens impair the ciliary activity of the
epithelial lining of the sinuses.
 Obstruction of the paranasal sinusal ostia which
impedes drainage.
 Bacterial multiplication in the sinus cavities.

Question 25

Diagnosis of Sinusitis

Answer 25

The diagnosis is made from clinical findings.
 Bacterial culture of the nasal discharge can be taken but is not very helpful as the recovered
organisms are generally contaminated by the resident flora from the nasal passage.
In chronic sinusitis, a careful dental examination, with sinus x
x-rays may be required. An antral
puncture to obtain sinusal specimens for bacterial culture is needed to establish a specific
microbiologic diagnosis.

Question 26

Treatment of Sinusitis

Answer 26

Antimicrobial therapy, a beta beta-lactamase resistant antibiotic such as amoxicillinamoxicillin-clavulanateclavulanate or cephalosporin may be used.

Question 27

What is acute otitis media?

Answer 27

Acute inflammation of the middle ear caused by infection.

Question 28

Characteristics of acute otitis media?

Answer 28

Otitis media indicates inflammation of the middle ear.
* Risk Factors: 3 3-7 years old, chronic sinusitis, chest disease…etc
* About 50% are caused by respiratory viruses.
* Bacterial: S. Pneumonia (40%) H. Influenza (30%), Moraxella Catarrhalis (

Question 29

Symptoms of Acute otitis media?

Answer 29

Ear pain
* Headache
* Neck pain with fluid drainage from the ear
* Fever
* Irritability
* Lack of balance
Hearing loss

Question 30

Pathogenesis of Acute Otitis Media

Answer 30

Commonly follows an upper respiratory
infection extending from the nasopharynx to
the middle ear.
 The presence of purulent exudate in the middle
ear may lead to meninges.

Question 31

What is the treatment of otitis media?

Answer 31

Choice for first first-line therapy is amoxicillin amoxicillin-clavulanate. In most adults, the dose is
amoxicillin 875 mg with clavulanate 125 mg.

Question 32

What is pharyngitis?

Answer 32

Pharyngitis is an inflammation of the pharynx.
* The aetiology can be bacterial, viral and fungal infections as well as non-infectious
aetiologies such as smoking.
* Most cases of acute pharyngitis are caused by viruses.
* Many of the viruses associated with the common cold syndrome may also result in
pharyngitis and include rhinoviruses, coronaviruses, enteroviruses, adenoviruses, influenza.
* Group A beta-haemolytic streptococcus or Streptococcus pyogenes is the most important
bacterial agent associated with acute pharyngitis

Question 33

What is the pathogenesis of pharyngitis?

Answer 33

As with common cold, viral pathogens in pharyngitis appear to
invade the mucosal cells of the nasopharynx and oral cavity,
resulting in oedema of the mucous membranes.

Question 34

What is the symptoms of pharyngitis

Answer 34

There are no clinical features that reliably distinguish viral and bacterial
causes:
 Red, sore, or “scratchy” throat.
 Vesicles or ulcers may also be seen on the pharyngeal walls.

Question 35

What is the treatment of pharyngitis?

Answer 35

For viral pharyngitis: symptomatic treatment only.
 Bacterial pathogens require antimicrobial therapy.
 Penicillin, or erythromycin for penicillin penicillin-allergic patients.

Question 36

What is Epiglottitis and Group Laryngotracheitis

Answer 36

Acute inflammation of the epiglottis, larynx, trachea caused by
infection.
* Haemophilus influenzae type b is the most common cause of
epiglottitis.
* Epiglottitis is less common in adults. Some cases of epiglottitis in
adults may be of viral origin.
* Most cases of laryngotracheitis are due to viruses including:
parainfluenza, influenza, adenovirus…

Question 37

What is epiglottis?

Answer 37

Serious obstructive inflammatory process that occurs principally in children between 2-5 but can occur outside of this.

Obstruction is supraglottic as opposed to the subglottic obstruction of laryngitis

Question 38

Epiglottitis and Group Laryngotracheitis
Pathogenesis

Answer 38

A viral infection may precede infection with H. influenzae in episodes of epiglottitis.
However, viral laryngotracheitis commonly begins in the nasopharynx and eventually moves into
the larynx and trachea. Inflammation and oedema involve the epithelium, mucosa and
submucosa of the subglottis which can lead to airway obstruction.

Question 39

What is the symptoms of Epiglottitis and Group Laryngotracheitis

Answer 39

Epiglottitis begins with fever
* Sore throat
* Hoarseness
* Drooling
* Dysphagia and progresses to severe respiratory distress
* Noisy breathing
* Barking cough

Question 40

How do we diagnose?
Epiglottitis and Group Laryngotracheitis

Answer 40

Pharyngeal swabs may be used to isolate pathogens in patients with laryngotracheitis, Virus
isolation, antigen detection Elisa, or PCR on nasopharyngeal aspirates.
* Epiglottic swabs for culture should be taken under direct vision by specialists, because swabbing
can precipitate acute airway obstruction. Blood cultures should also be sent. Lateral radiographs
of the neck may show the enlarged epiglottis.
* ImmunofluorescentImmunofluorescent-antibody staining to detect virus in sputum, pharyngeal swabs, or nasal washings.

Question 41

What is the recommended treatment for Epiglottitis and Group Laryngotracheitis

Answer 41

Haemophilus influenzae type b conjugated vaccine is recommended for all pediatric patients.
* Intubation and ventilation may be necessary.
* Intravenous antibiotic therapy should be instituted immediately.
Epiglottitis and Group Laryngotracheitis

Question 42

What is Dipheria?

Answer 42

An acute upper respiratory tract or skin infection, caused by toxin toxin-producing strains of
Corynebacterium diphtheriae with central nervous system and cardiac complications.
* After the introduction of immunisation, diphtheria became rare in the developed world, but still
common in developing countries.
* The microorganism is transmitted by aerosol spread, but infected skin lesions can also act as
reservoirs for infection.
* Diphtheria can be treated, but in advanced stages, diphtheria can damage the heart, kidneys
and nervous system. Even with treatment diphtheria can be deadly, especially in children.

Question 43

What is the pathogenesis of diphtheria?

Answer 43

The microorganism colonises the pharynx, multiplies and produces a toxin.
* The toxin produced by pathogenic strains of C. diphtheriae inhibits protein synthesis.
* It acts locally to destroy epithelial cells and phagocytes, resulting in the formation of a prominent
exudate, sometimes termed a ‘false membrane’.
* Cervical lymph nodes become grossly enlarged (‘bull bull-neck’ appearance).
* The membrane and swelling can cause airway obstruction and death.
* The toxin also spreads via the lymphatics and blood, resulting in myocarditis and polyneuritis.

Question 44

What are the symptoms of Diphtheria?

Answer 44

Fever and pharyngitis with a false membrane that
may cause airway obstruction; enlarged cervical
lymph nodes; myocarditis with cardiac failure; and
polyneuritis.
* In skin infections, chronic ulcers with a membrane
form and toxicity is mild.

Question 45

How is Diphtheria characterised?

Answer 45

a |
Characteristic bull neck caused by enlarged lymph nodes. b | Thick pseudomembrane in the
posterior pharynx. The pseudomembrane is a layer of bacteria and debris from necrosis of the
surrounding tissues due to diphtheria toxin. c | Cutaneous lesion caused by Corynebacterium diphtheriae.

Question 46

How is diphtheria diagnosed?

Answer 46

Diphtheria is confirmed by isolation of Corynebacterium spp.
* Throat swabs, detection of toxins by ELISA and/or PCR.
* Demonstrating toxin is essential, because non non-toxin producing strains of C. diphtheriae do not cause diphtheria.

Question 47

How is Diphtheria treated>

Answer 47

Treatment should be commenced before laboratory confirmation and includes antitoxin and
antibiotics (penicillin or erythromycin).
* The main treatment is DAT, which contains antibodies obtained from the serum of horses that
have been immunized against DT .
* Diphtheria is a notifiable infection in the UK
* Diphtheria control is mainly based on immunization of the population through vaccination

Question 48

What are LTRI?

Answer 48

The ‘upper respiratory tract’ is separated from the ‘lower
respiratory tract’ at the level of the vocal cords. Lower respiratory
tract infections therefore include those affecting the trachea,
bronchi, bronchioles and lung parenchyma.
 These syndromes, especially pneumonia, can be severe or fatal.
 Although viruses, and fungi can all cause lower respiratory tract
infections, bacteria are the dominant pathogens; accounting for a
much higher percentage of lower than of upper respiratory tract
infections.

Question 49

what is bronchitis and bronchiolitis?

Answer 49

Bronchitis and bronchiolitis involve inflammation of the bronchial tree.
 Bronchitis is usually preceded by an upper respiratory tract infection.
 Chronic bronchitis with a persistent cough and sputum production is caused by a combination of
environmental factors, such as smoking, and bacterial infection H. influenzae influenzaeand S. pneumoniae pneumoniae.
 Bronchiolitis is a viral respiratory disease of infants and is caused primarily by respiratory
syncytial virus virus, parainfluenza viruses, influenza viruses.
 Bronchiolitis occurs mainly in children aged less than 2 years; it is particularly severe in infants
aged less than 6 months.

Question 50

How does bronchiolitis and bronchitis differ?

Answer 50

Bronchioles vs bronchi swelling!

Question 51

Pathogenesis of Bronchitis and bronchiolitis?

Answer 51

When the bronchial tree is infected, the mucosa becomes hyperaemic and oedematous and
produces bronchial secretions.
* The damage to the mucosa can range from simple loss of mucociliary function to actual
destruction of the respiratory epithelium.
* Exudate made up of necrotic material and respiratory secretions lead to airway obstruction.

Question 52

Symptoms of Bronchitis and Bronchiolitis?

Answer 52

Symptoms of an upper respiratory tract infection with a cough.
* Mucopurulent sputum may be present.
* Fever is common.
* Wheezing or an actual lack of breath sounds may be noted.

Question 53

What is the diagnosis process for Bronchitis and Bronchiolitis

Answer 53

Bacteriologic examination and culture of purulent respiratory secretions.
* Aspirations of nasopharyngeal secretions or swabs for viral culture in infants with bronchiolitis.
* Serologic tests demonstrating a rise in antibody titre to specific viruses.
* fluorescentfluorescent-antibody staining, ELISA and/or PCR.

Question 54

What is treatment for bronchitis and bronchiolitis?

Answer 54

Treat symptoms
* Antimicrobials usually not helpful.
* Corticosteroids, bronchodilators, or prophylactic antibiotics.

Question 55

What is pneumonia?

Answer 55

Pneumonia is common, with a significant morbidity and mortality
* This is an important infection worldwide. It is most common in the winter months
* >2 million cases in UK in 2018
* 2nd leading cause of hospitalization in UK
* Leading cause of death (~20,000 deaths) ~10% of patients with pneumonia die
* Pneumonia is an inflammation of the lung parenchyma
* Numerous factors, including environmental contaminants and autoimmune diseases, as
well as infection, may cause pneumonia
* Streptococcus pneumoniae is the most common agent of community community-acquired acute
bacterial pneumonia

Question 56

How does pneumonia enter?

Answer 56

Microbes constantly enter airways
but many factors prevent colonisation

Question 57

How does pneumonia colonise?

Answer 57

Disrupting or overwhelming these defense mechanisms can allow microbes to colonise the lungs resulting in pneumonia

Question 58

What different types of pneumonia are there?

Answer 58

Community-acquired pneumonia pneumonia.
* Hospital -acquired pneumonia ; HAP is a pneumonia presenting two or more days after
admission to hospital. One of the most common nosocomial infections
* Pneumonia in immuno immuno-compromised individuals individuals;
* Aspiration pneumonia ; Patients may aspirate oropharyngeal or gastric contents into their
upper and lower airways. The initial insult is a chemical pneumonitis, but infection may
develop later

Question 59

What are the symptoms of pneumonia?

Answer 59

Malaise
 Fever
 Shortness of breath
 Productive cough
 Pleuritic chest pain
 Tachypnoea
 Tachycardia
 Focal chest signs e.g. crackles, cyanosis, hypoxia and confusion.
 Severe cases lead to bloodstream infection and severe sepsis with circulatory collapse and
multiorgan failure.

Question 60

What is the pathogenesis of pneumonia?

Answer 60

Infectious agents gain access to the lower respiratory tract by the inhalation of aerosolised
material or by aspiration of upper airway flora.
* Pneumonia occurs when lung defence mechanisms are overwhelmed.

Question 61

What is CAP pathogenesis

Answer 61

1. arrival of pathogens in alveolar space
2. Uncontrolled multiplication of pathogens
3. local production of cytokines primarily by alveolar macrophages
4. Recruitment of neutrophils into the alveolar space and introduction of cytokines into systemic circulation

Question 62

How do we diagnose pneumonia?

Answer 62

Sputum specimens for culture and microscopy (Gram stain) – only occasionally useful, not
routinely recommended.
* Blood cultures (positive in 15% of cases cases).
* Urine antigen detection for pneumococcal infectioninfection.
* Polymerase chain reaction (PCR) now commonly replacing serology for viruses, Mycoplasma,
Chlamydophila and Coxiella infectionsinfections.
* Serology (viruses and Mycoplasma, Chlamydia, Coxiella and Legionella species species).
* Bronchoalveolar lavage (BAL) specimens obtained by bronchoscopy for microscopy, culture and
direct immunofluorescence tests .
* Chest radiograph: lobar, patchy or diffuse shadowing . Radiological changes often lag behind
clinical course and are not predictive of the microbiological cause.

Question 63

How do we treat pneumonia?

Answer 63

Once a diagnosis is made, t herapy is directed at the specific organism responsible.
* Management of gas exchange and fluid balance are important.
* The pneumococcal vaccine should be given to patients at high risk .
* In AIDS patients, trimethoprim/sulfamethoxazole, aerosolized pentamidine or other
antimicrobials can be given for prophylaxis.