L68 – Lower Respiratory Tract Infections I Flashcards by Max Kam

What is the name of the inflammation in subglottis area?

Traceholaryngobronchitis (CROUP)

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Age most affected by Traceholaryngobronchitis ?

Relatively common in children: 3 months to 3 years (peak incidence at 2 years of age)

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Aetiology of Traceholaryngobronchitis? (name of bacteria, viruses)

Mainly viruses
 Parainfluenza virus
 Influenza virus
 Respiratory syncytial virus (RSV)

Also Mycoplasma pneumoniae

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What are some specific symptoms of Traceholaryngobronchitis?

Fever
Laryngitis **
Inspiratory stridor **
(= high-pitched wheezing due to disrupted airflow in upper airway)
-Dyspnea (shortness of breath) / tachypnoea

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What symptom of Traceholaryngobronchitis that may not manifest?

respiratory distress

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What symptoms of Tracheolaryngobronchitis result in abnormal sound in breathing? (List the sounds)

**Rales (abnormal lung sounds: discontinuous clicking / rattling)

**Wheezing (in lower airway)

**Inspiratory stridor (= high-pitched, wheezing in Upper airway)

Distinctive cough

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Describe the distinctive cough in tracheolaryngobronchitis?

 Deep, brassy tone (seal’s bark)

 Hoarseness (due to swollen vocal cord)

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What is the method of aetiological diagnosis of tracheolaryngobronchitis?

swab&raquo_space; viral antigen detection, nucleic acid amplification

optional viral culture (not routine)

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What is the CXR appearance of tracheolaryngobronchitis?

tapering of tracheal width (narrows toward the top)&raquo_space; steeple sign**

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What are the treatment options for Tracheolaryngobronchitis?

Supportive care, e.g.:
 Oxygen, ventilatory support

 Nebulized bronchodilators (for wheezing in lower airway)

 Fluid replacement

no antibiotic due to usual viral aetiology

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What is the aetiology of Pertussis?

Aetiology:

Bordetella pertussis (= Gram-negative coccobacillus)

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What are the 2 steps in the pathogenesis of Pertussis?

Filamentous haemagglutinin (FHA) attaches to ciliated respiratory epithelium
Produce toxins to damage epithelium

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Name some toxins made by Bordetella pertussis?

**pertussis toxin,
**adenylate cyclase toxin,
tracheal cytotoxin

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What is the transmission of Pertussis?

Transmitted by respiratory droplets** (>5 μm, not airborne)

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What is the incubation period of pertussis?

incubation period: <1 week to >3 weeks

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Pertussis affects which age groups most?

Attack rate = highest in children

Also Common cause of chronic cough in adolescents, adults

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Pertussis outbreaks are community or nosocomial (hosptial)?

Both

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What are the 3 classical phases of Pertussis? CPC

Catarrhal
Paroxysmal
Convalescent

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Are the symptoms of pertussis the same in adults and children?

if adult have partial immunity

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What are the clinical presentations of Pertussis in Catarrhal phase?

Rhinorrhea (= runny nose)
Conjunctival injection / bleeding
Malaise
Low grade fever
Chronic dry cough

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What are the clinical presentations of Pertussis in Paroxysmal phase?

Short expiratory bursts followed by deep inspiratory gasp (whooping cough)

Terminates with vomiting

Cyanosis

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What are the clinical presentations of Pertussis in Convalescent phase?

recovering from illness: e.g. 100 days (百日咳)

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Method of definitive diagnosis of Pertussis?

Culture of nasopharyngeal aspirate / swab on Bordet-Gengou medium

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What is the limitation of Culture of nasopharyngeal aspirate / swab on Bordet-Gengou medium to diagnose pertussis?

Not sensitive: usually just positive in catarrhal phase of Pertussis

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Apart from Culture of nasopharyngeal aspirate, what are the 2 other methods of diagnosing pertussis?

PCR of nasopharyngeal specimens Serology

What are the shortcomings of using serology to diagnose pertussis?

 Not widely available  May not be useful in acute infections (need paired sera)

What is the treatment for pertussis?

Specific antibiotic: macrolides*** inhibit 50S (e.g. erythromycin, clarithromycin, azithromycin)

What are the different MoA in macrolides given to pertussis during catarrhal and paroxysmal phase?

- Give in catarrhal phase = ↓ duration of infection | - Give in paroxysmal phase: same duration, but ↓ infectivity (less serious complications)

List come complications of Pertussis?

- pneumonia - haemorrhage - pneumothorax - CNS abnormalities (convulsion, encephalopathy)

Method of preventing pertussis? **

vaccination

What are the 2 forms of vaccines for Pertussis?

Whole-cell killed vaccine: protection not lifelong Acellular pertussis (aP) vaccine

What virulent factors of Bordetella pertussis is contained in to acellular pertussis (aP) vaccine?

filamentous haemagglutinin, pertussis toxin

Which form of vaccine for Pertussis is used in Hong Kong, why?

Acellular pertussis (aP) vaccine Given in a quadrivalent vaccine against diphtheria, tetanus, pertussis and poliomyelitis

Describe pneumonia?

inflammation affecting lung parenchyma (terminal / respiratory bronchioles)

What are the routes of infection of pneumonia?

Direct inhalation of infectious particle Aspiration of secretion from mouth and nasopharynx (Rare) Haematogenous spread from another foci of infection in body

How does age affect the type of pathogen that causes pneumonia?

Elderly > usually bacteria (e.g. Staphylococcus aureus, Mycoplasma pneumoniae) Children > usually virus (e.g. RSV, parainfluenza)

Name some hospital acquired pneumonia pathogens?

Escherichia coli, Pseudomonas aeruginosa, MRSA

Name some Community acquired pneumonia pathogens?

Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, viruses (RSV, parainfluenza)

When taking pneumonia patient history, what are some inquiries to help differentiate the type of pathogen?

Age Underlying illness (e.g. immunocompromised?) Occupation and travel Animal contact

Pulse-temperature deficit is a physical examination feature of pneumonia. Explain what it is.

When temperature elevations are not accompanied by a physiologic increase in the pulse

What extracts/fluids are used for culture for pneumonia?

respiratory tract specimens, blood, pleural fluid

What is the CXR result of pneumonia?

Cystic cavities Diffuse, white lungs with lots of consolidation

How does the characteristics of sputum give clue about the pathogen causing pneumonia? Give 2 examples

‘Rusty’ sputum (dark red due to pulmonary hemorrhage) = Streptococcus pneumoniae ‘Currant-jelly’ sputum (thick, mucoid) = Klebsiella pneumoniae

From pneumonia patient: After gram satin of sputum, what cells are expected to be very abundant?

- Predominant flora - lot of leukocytes - Epithelial cells

What mediums are used to culture pneumonia pathogens?

blood agar, chocolate agar, selective media

When is Nucleic acid amplification tests used in diagnosis of pneumonia?

upon suspicion of:  Viruses  ‘Atypical’ bacterial pathogens, e.g. Mycoplasma pneumoniae

What are some atypical bacterial pathogens that require PCR to diagnose pnuemonia?

Mycoplasma pneumoniae, Chlamydia / Chlamydophila, Legionella

Name the 3 viral investigations on respiratory specimens?

 Antigen detection (e.g. direct immunofluorescent staining)  Viral culture  Nucleic acid amplification tests (e.g. PCR)

Which invasive method of collecting respiratory tract specimen gives better sample of lower resp. tract?

Fibreoptic Bronchoscopy + brochoalveolar lavage/ bronchial aspirate

When is Nasopharyngeal aspirate used?

mainly for respiratory viruses

What are the 4 types of respiratory tract aspirations to collect samples? PENT

Pleural aspiration Endotracheal aspiration Nasopharyngeal aspirate Transtracheal aspiration

Urine antigen detection test is used for which pathogens in pneumonia?

Streptococcus pneumoniae, Legionella pneumophila serogroup 1

What is the empirical therapy for pneumonia?

1 beta lactam antibiotic (e.g. penicillins / cephalosporins) ± 1 macrolide (e.g. erythromycin, clarithromycin, azithromycin) or tetracycline

Difference in treatment of mild and severe pneumonia?

Mild = outpatient discharge with oral antibiotics Severe = Inpatient with IV antibiotics, then oral

What are the classic symptoms of Acute community-acquired pneumonia?

``` Acute onset of fever, chills, pleuritic chest pain, cough, mucopurulent sputum ```

What bacteria causes post- epidemic / pandemic influenza secondary bacterial pneumonia?

Streptococcus pneumoniae Staphylococcus aureus (less common)

What is the most common bacteria causing Acute community-acquired pneumonia (CAP)?

Streptococcus pneumoniae Causes pneumococcal pneumonia

What are the 2 types of pneumococcal | vaccines?

1. Polysaccharide vaccine (23-valent) | 2. Conjugate vaccine (13-valent)

List the top 3 bacteria that cause Acute community-acquired pneumonia (CAP)?

Streptococcus pneumoniae Haemophilus influenzae Staphylococcus aureus

In patients with COPD, cystic fibrosis and broncheictasis, what is the bacteria most likely to cause pneumonia?

Pseudomonas aeruginosa

Why is Atypical pneumonia syndrome called "walking pneumonia"?

- Routine culture reveals no pathogen - Prolonged course of illness - Not appear very ill

Atypical pneumonia syndrome is unresponsive to which antibiotics? Thus require which antibiotics to treat?

Not responding to beta lactam antibiotics may need macrolides, tetracyclines

Atypical pneumonia syndrome is most commonly caused by which bacteria?

Mycoplasma pneumoniae | less common= Chylamydophila pneumoniae, Legionella pneumophila

Is Serology or urine antigen detection/ Nucleic acid amplification used for atypical pneumonia syndrome?

Urine antigen detection/ Nucleic acid amplification Serology takes too long

What age group is most affected by atypical pneumonia syndrome?

Can affect any age group | often more severe in the elderly

What bacteria causes Legionellosis?

Legionella pneumophila

Describe the O2 requirement, gram stain, spore and morphology of Legionella pneumophila.

aerobic, Gram negative, non-spore-forming bacilli

What is the reservoir of Legionella pneumophila?

natural, artificial fresh water environments

Route of transmission for Legionella pneumophila?

aerosol, aspiration

What are the 2 clinical diseases caused by Legionella pneumophila? PL

Pontiac fever** Legionnaires’ disease

Describe Pontiac fever?

acute, self-limiting, flu-like illness without pneumonia

What are some symptoms of Legionnaires disease?

pneumonia diarrhea, nausea, vomiting, abdominal pain

What is the best detection method of Legionella pneumophila?

Urine antigen detection

Which antibiotics are used for Legionella pneumophila?

 Macrolide (erythromycin, clarithromycin, azithromycin) Fluoroquinolone (ciprofloxacin, levofloxacin)

Which antibiotics are NOT used for Legionella pneumophila?

 Beta lactam (penicillin, cephalosporin) are generally not effective

Name 3 unique risk factors of hospital acquired pneumonia?

Altered mental status ventilator-associated pneumonia** Reduced gastric acidity

Aetiology of hospital acquired pneumonia?

- Aerobic Gram negative bacteria - Non-fermenters bacteria - multi-resistant bacteria

Give examples of Aerobic Gram negative bacteria that causes hospital acquired pneumonia?

Enterobacteriacae (ferment glucose), e.g. Escherichia coli, Klebsiella pneumoniae

Give examples of Non-fermenters bacteria that causes hospital acquired pneumonia?

Pseudomonas aeruginosa, Acinetobacter baumannii

Give examples of multi-resistant bacteria that causes hospital acquired pneumonia?

methicillin-resistant Staphylococcus aureus (MRSA)

What conditions predisposes to aspiration pneumonia?

when consciousness is altered, IMPAIRED gag and swallowing reflexes e.g. alcoholism, cerebrovascular disorders, convulsion

What are the 3 important pathological mechanisms for aspiration pneumonia? Which of these mechanisms are acute? BronBacChem

1. Chemical pneumonitis 2. Bronchial obstruction with particulate matter (e.g. food) 3. Bacterial aspiration pneumonia 1 and 2 are acute, 3 takes time

What are some clinical representations of aspiration pneumonia?

fever, weight loss, productive cough, putrid sputum (rotting smell)

What is the predominant pathogen causing aspiration pneumonia?

Predominantly the oral flora: anaerobes, (community-acquired) Strep. Other bacteria: gram negative bacilli, staph. aureus

Treatment for aspiration pneumonia?

broad spectrum coverage against aerobic and anaerobic organisms

What are 3 causes of empyema thoracis?

Complication of: 1) Pneumonia 2) Intrathoracic surgery or trauma 3) Subdiaphragmatic sepsis

Pathogens that cause empyema thoracis?

After pneumonia: Staphylococcus aureus, Streptococcus pneumoniae After surgery/ trauma: Anaerobes Aerobic Gram negative bacilli (i.e. Staphylococcus aureus)

Treatment for empyema thoracis?

Prolonged antibiotics Adequate drainage of abscess Decortication (surgical removal of fibrous tissue)

Poor dental hygiene with periodental disease can predispose to what condition?

Lung abscess

Name some predisposing factors of lung abscess apart from poor dental hygiene?

- Aspiration of mixed oral flora - IE, bacteraemia - Bronchiectasis - Bronchial obstruction - Cavitating pulmonary infection

L68 – Lower Respiratory Tract Infections I Flashcards

(90 cards)