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RHS- Micro > Respiratory Infections 4 > Flashcards

Respiratory Infections 4 Flashcards

1
Q

Bordetella pertussis : Biology

A

Gram –ve coccobacillus

• Fastidious, requires special media

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2
Q

What agar does Bordetella pertussis use

A

Regan Lowe, Bordet-Genou agar
• Charcoal blood agar + cephalosporin
• Samples acquired from ciliated nasal epithelium

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3
Q

How to prevent B. pertussis

A

Acellular Pertussis “aP” component of the DTaP/Tdap vaccine
• Pertussis Toxin (PT), Filamentous hemagglutinin (FHA), Pertactin
• Recommended for infants
• Tdap booster strongly recommended for pregnant woman to prevent
transmission from mom to neonate

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4
Q

B. pertussis: Pathogenesis part 1

A
  • Infectious aerosol droplets are inhaled
  • Filamentous Hemagglutinin (FHA), Pertactin, fimbriae facilitate tight binding to ciliated epithelium of nose, trachea, bronchi
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5
Q

B. pertussis: Pathogenesis part 2

A

Virulence Activation

Colonization impairs ciliary function
Bacteria secrete Tracheal Cytotoxin (direct damage) and Pertussis/Adenylyl Cyclase Toxin (alters GCPR signaling pathways)

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6
Q

B. pertussis: Pathogenesis part 3

A

Contribution of Host Immune response
• Cilia damage contributes to necrosis
• Leukocytes fail to migrate to infected tissue (leukocytosis)
• Excessive mucus production contribute to cough severity

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7
Q

Which toxin from b pertussis is an
• A-B type Exotoxin
• Inactivates α-subunit GCPR via ADP ribosylation
• Inhibits immune signaling and chemotaxis

A

Pertussis Toxin

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8
Q

What does Adenylyl Cyclase Toxin do

A

• Increases cAMP levels of respiratory epithelium
• Contributes to immune cell dysregulation and
increased mucus production

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9
Q

Whooping Cough aka Tracheobronchitis has three stages

A

Stage 1: catarrhal (1-2weeks)
Stage 2: paroxysmal (1-6weeks)
Stage 3: convalescence (2-3 weeks; susceptible to other respiratory infections)

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10
Q

Clinical Presentation:

Whooping Cough aka Tracheobronchitis stages

A 
Stage 1 Catarrhal
• Common cold/Rhino- pharyngitis
Stage 2 Paroxysmal
• Sore throat
• Intense coughing
episodes, followed by a “whoop”
• Productive clear sputum
• Vomiting
• Hypoxia/Cyanosis
• Lab Finding: Predominant lymphocytosis
Stage 3 Convalescence
• Residual cough
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11
Q

Which pathogen causes croup

A

Parainfluenza PIV

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12
Q

Paramyxoviridae Family Biology

A 
• Enveloped ss(-)RNA genome in helical nucleocapsid
• Includes: 
Parainfluenza Virus PIV
Respiratory Syncytia Virus RSV
Human Metapnemovirus (HMV)
Measles Virus
Mumps Virus
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13
Q

Paramyxoviridae pathogenic features

A

Attachment
PIV = HN (Hemagglutinin-Neuraminidase)
RSV, HMV = G-protein

Entry-Penetration
PIV, RSV, HMV = F protein

Genome Synthesis
PIV, RSV, HMV = L protein “Large” RNA- Dependent RNA Polymerase

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14
Q

Parainfluenza PIV Epidemiology

A
  • Very common respiratory pathogen esp. pediatric population
  • 4 Serotypes: PIV-1, PIV-2, PIV-3, PIV-4
  • Croup is most common in children < 5 years old
  • Adults can be asymptomatic carriers
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15
Q

Predisposing factors of PIV

A
  • Asthma
  • Vitamin A deficiency
  • Lack of breastfeeding
  • Environmental smoke or toxins
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16
Q

Transmission of PIV

A

Respiratory droplets or via directs person-to-person contact with infected secretions or fomites

17
Q

Type of PIV or HPIV seen In croup

A

Croup (Laryngeotracheobronchitis)

HPIV-1, HPIV-2, HPIV-3

18
Q

Most common cause of bronchiolitis

A

Respiratory Syncytia Virus RSV

- followed by rhinovirus

19
Q

Parainfluenza PIV Pathogenesis

A
  • HN on virion acts as VAP; binding to host receptor sialic acid on respiratory epithelial cells
  • Fusion F-protein has a hydrophobic fusion peptide which is exposed after VAP attaches.
  • F-protein inserts into host membrane, triggering fusion of virion and target cell lipid bilayer membranes.

Viral replication leads to surface expression of F-protein, leading to fusion to new cells aka syncytium formation.

Viral replication, syncytia and host response trigger inflammation for lining larynx, trachea and bronchi.

20
Q

Clinical Presentation of Croup Laryngo-tracheo-bronchitis

A

Subglottic narrowing of trachea: steeple sign
Onset 3-7 days
Resolution 10 days

  • Preceded by non- specific URTI
  • Fever (<38°C)
  • Sore throat
  • Inspiratory stridor
  • Barking Cough
  • Hoarseness
  • Occasionally vomiting
21
Q

Leading cause of LRTIs in infants and young children

A

Respiratory Syncytia Virus RSV

22
Q

When does HPIV peak ?

A

Fall

23
Q

When does RSV peak

A

Winter

24
Q

RSV: Pathogenesis

A
  • G-protein mediate attachment; F-protein mediates fusion
  • Virions directly invade the respiratory epithelium, leading to syncytia formation, which is followed by immunologically-mediated cell injury.
  • Necrosis of the bronchi and bronchioles leads to the formation of “plugs” of mucus, fibrin, and necrotic material within smaller airways.
25
Q

Progression of RSV PATHOGENESIS leads to

A

Infection can progress to alveolar sacs (atypical interstitial pneumonia) or trigger Bacterial Secondary Super- infections

26
Q

What does this picture show

A

Section of Lung with Respiratory Syncytial Virus infection. H&E A &B: Necrosis, inflammation and syncytial giant cell formation (note the eosinophilic para-nuclear inclusions, arrows).

27
Q

Clinical Presentation:

Bronchiolitis – Interstitial Pneumonia

A
  • Preceded by non- specific URTI
  • Onset ~7 days
  • Fever (<38°C)
  • Respiratory distress (↑ RR, retractions, wheezing, crackles)
  • Atelectasis
  • Hypoxia, cyanosis
28
Q

What is seen on chest radiograph of Respiratory Syncytial Virus pneumonia and bronchiolitis.

A

Bilateral interstitial infiltrates, hyper-expansion of the lung, and right upper lobe atelectasis (arrow) are present.

29
Q

Human Metapneumovirus HMPV biology

A

Family: Paramyxoviridae
• Genetically, Epidemiologically similar to RSV
• Clinical Presentations are similar to RSV
• Non-specific febrile disease, Bronchitis, Bronchiolitis, Pneumonia

30
Q

Confirmatory differential diagnosis For RSV vs HMPV requires

A

RT-PCR

31
Q

Bronchitis prognosis

A

▪ Good outcome, usually self-limiting
▪ 90% Bronchitis is viral and does not require antibiotics
▪ Antibiotics for Whooping cough will shorten the course
▪ Complications include interstitial pneumonia (esp. infants) exacerbation of asthma and COPD, bronchiectasis, rib fracture

32
Q

Examples of LRTI (corresponds to pathogens in this set)

A
  • Laryngotracheitis
  • Bronchitis
  • Bronchiolitis
  • Pneumonia/Pneumonitis
33
Q

Examples of URTI

A
  • Rhinitis/Rhinosinusitis
  • Sinusitis
  • Otitis Media
  • Epiglottitis
  • Pharyngitis/Tonsillitis
34
Q

How to prevent bronchitis

A

▪ TDaP/Tdap vaccines, esp for infants and pregnant women
▪ Post-exposure prophylaxis can be used for contacts of person infected with B. pertussis
▪ Ribavirin antiviral recommended for severe RSV

RHS- Micro (8 decks)

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