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Respiratory Block: Microbiology > Upper Respiratory Tract Infections > Flashcards

Upper Respiratory Tract Infections Flashcards

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1
Q

What are the most common organisms that colonize the URT mucous membranes?

A
  1. Viridans Streptococci
  2. Beta-haemolytic Streptococci
  3. Streptococcus Pneumoniae
  4. Moraxella Catarrhalis
  5. Anaerobic Bacteria
  6. Yeasts
  7. Viruses
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2
Q

Pathogenesis of URTIs: ENTRY

A
  1. Ingestion (uncommon)
  2. Inoculation
  3. Inhalation (most common)
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3
Q

Pathogenesis of URTIs: ADHERENCE

A
  1. Fimbriae
  2. Surface polysaccharides
  3. Capsular components
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4
Q

Pathogenesis of URTIs: Function of AGGRESSINS

A

Allow proliferation of organism by evasion of host defenses

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5
Q

Pathogenesis of URTIs: AGGRESSINS

A
  1. IgA Protease
  2. Capsule
  3. Various enzymes
  4. Surface proteins
  5. CHO
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6
Q

Pathogenesis of URTIs: TOXINS

A
  1. Endotoxins

2. Exotoxins

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7
Q

What is the most frequent nasopharyngeal infection?

A

The “common cold”

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8
Q

Common Cold: Causative agents

A
  1. Rhinovirus
  2. Coronavirus
  3. Parainfluenza Virus
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9
Q

Common Cold: clinical course

A

Usually mild, self-limiting, catarrhal syndrome

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10
Q

Common Cold: Transmission

A
  1. Direct contact with surfaces / secretions

2. Inhalation

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11
Q

Common Cold: complications

A

A small number may be complicated by bacterial infections

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12
Q

What is pharyngitis?

A

Inflammation of the pharynx, usually due to infection

- may occur without tonsillitis

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13
Q

What typical triad is seen in Acute Pharyngitis?

A
  1. Sore throat
  2. Fever
  3. Pharyngeal inflammation
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14
Q 
Pharyngitis: etiological agents 
Which class of agents is the most common cause?
A

Viruses!

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15
Q

Pharyngitis: etiological agents

Which specific viruses are causative agents?

A
  • EBV
  • adenovirus
  • enterovirus
  • Herpes Simplex
  • rhinovirus
  • coronavirus
  • CMV
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16
Q

Pharyngitis: etiological agents

What can primary EBV infection cause?

A

Infectious Mononucleosis Syndrome

- multi-system disorder, presentation may include fever, pharyngitis, and adenopathy

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17
Q

Pharyngitis: etiological agents

What is the most common bacterial cause?

A

S. Pyogenes (Group A most common)

S. Pyogenes group C and group G also seen

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18
Q

Pharyngitis: etiological agents

Less common causative agents

A
  1. Arcanobacterium Haemolyticum

2. Corynebacterium Diptheriae

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19
Q

Pharyngitis: etiological agents

Other causative agents

A
  1. Neisseria Gonorrhoeae
  2. Mycoplasma Pneumoniae
  3. Chlamydiphilia Pneumoniae
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20
Q

How can the common cold lead to bacterial infection?

A

Two methods:
1. Damage cilia
2. Cause up-regulation of different receptors
Both make it easier for bacteria to bind
= not to bad infection that suddenly gets worse (added bacterial superinfection)

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21
Q

What is the most common cause of pharyngitis in school aged children?

A

Group A Streptococcus Pyogenes

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22
Q

What two main complications are seen as a result of infection with Group A Streptococcus?

A
  1. Rheumatic Fever

2. Glomerulonephritis

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23
Q

What happens if EBV is treated incorrectly with Ampicillin?

A

It precipitates a rash

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24
Q

Pharyngitis Caused by Streptococcus Pyogenes:

Microbial classification

A

Gram positive cocci in chains

- Group A Beta-haemolytic streptococcus

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25
Q

Pharyngitis Caused by Streptococcus Pyogenes:

Clinical Features

A
  • fever
  • sore throat
  • enlarged regional lymph nodes
  • bright red pharynx; inflamed and oedematous pharyngeal mucosa
  • exudates may be present
  • can have tonsillitis with pus in the follicles
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26
Q

Pharyngitis Caused by Streptococcus Pyogenes: Diagnosis

A

Difficult to distinguish from viral causes.

  1. Gold Standard: throat swab for culture (not widely feasible in SA)
  2. RADTs: rapid antigen detection tests (not as sensitive and expensive)
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27
Q

Pharyngitis Caused by Streptococcus Pyogenes: Treatment

A

Penicillin (no resistance)

- Stat IM or 10 days oral

28
Q

Pharyngitis Caused by Streptococcus Pyogenes: Treatment in penicillin allergy

A

Macrolides (some resistance is however present)

29
Q

Complications of Streptococcal Pharyngitis: Broad categories

A
  1. Suppurative

2. Non-Suppurative

30
Q

Complications of Streptococcal Pharyngitis: Suppurative Complications

A
  1. Peritonsillar Cellulitis
  2. Peritonsillar Abscess
  3. Retropharyngeal Abscess
  4. Acute Sinusitis
  5. Acute Otitis Media
31
Q

Complications of Streptococcal Pharyngitis: What is a retropharyngeal abscess?

A

Collection of pus in tissues at the back of the throat.

= potentially life threatening airway obstruction and sepsis

32
Q

Complications of Streptococcal Pharyngitis: What is the clinical presentation of a retropharyngeal abscess?

A
  • dysphagia
  • stridor
  • odynophagia
33
Q

Complications of Streptococcal Pharyngitis: What is the treatment of a retropharyngeal abscess?

A

Surgical drainage plus antibiotics required

34
Q

Complications of Streptococcal Pharyngitis: What are the non-Suppurative complications?

A
  1. Acute Rheumatic Fever

2. Acute Glomerulonephritis

35
Q

Complications of Streptococcal Pharyngitis: What other complication may be seen?

A

Scarlet Fever

36
Q

Diphtheria: causative agent

A

Caused by toxin producing strains of Corynebacterium Diphtheriae

37
Q

Diphtheria: what does the toxin do?

A

Causes necrosis of tissues

38
Q

Diphtheria: Most common clinical presentation

A

Most commonly presents as a Pseudomembranous Pharyngitis

  • associated with swelling of the tonsils, uvula, cervical lymph nodes, submandibular region and anterior neck
  • can cause respiratory obstruction
39
Q

Diphtheria: spread

A

Diphtheria toxin can reach the bloodstream

  • myocarditis
  • demyelinating peripheral neuritis
40
Q

Diphtheria: presentation of cutaneous diphtheria

A

Cutaneous diphtheria presents as chronic non-healing ulcers

Usually less severe, but can spread and cause diphtheria pharyngitis

41
Q

Diphtheria: spread

A

Via respiratory droplets or direct contact with infected skin lesions or respiratory secretions

42
Q

Diphtheria: how common is it in SA?

A

Uncommon in SA and other countries that have implemented effective immunization programs

43
Q

Diphtheria: management

A
  1. Inform lab of suspected Diphtheria (collect swabs)
  2. Notifiable condition
  3. Isolate Patient
  4. Diphtheria antitoxin to neutralize toxin (must start ASAP, even before diagnosis is confirmed)
  5. Penicillin for 14 days to eliminate organism from nasopharynx and prevent spread to others
44
Q

Diphtheria: Management of close contacts

A

Close contacts require:

  • chemoprophylaxis
  • booster vaccination
  • throat swab to establish carrier status
45
Q

What is epiglottitis?

A

Rapid onset of acute inflammation and intense oedema of the epiglottis

46
Q

Before immunization what is epiglottitis almost always caused by?

A

Haemophilus Influenzae Type B

47
Q

What is the classification of Haemophilus Influenzae?

A

Pleomorphic gram-negative bacilli

48
Q

Who is usually affected by epiglottitis?

A

Usually in children 2-4 years

49
Q

What has decreased the incidence of epiglottitis?

A

Incidence has decreased since the introduction of the Hib vaccine

50
Q

What are other rarer causes of epiglottitis?

A
  • other Haemophilus spp
  • Pneumococci
  • Streptococci
  • Staphylococci
51
Q

What is the clinical presentation of epiglottitis?

A

Fever, drooling (dysphagia), cervical lymphadenopathy, respiratory distress, can lead to obstruction stridor and death.

52
Q

What is an important consideration in the assessment / management of a patient with epiglottitis?

A

In oedematous “cherry red” epiglottitis, examination of the throat may provoke respiratory arrest.
- If touch epiglottis, need someone experienced with intubation to secure airway immediately (EMERGENCY!)

53
Q

How is epiglottitis treated?

A

Secure airway and ceftriaxone!
- do cultures: surface of epiglottis and blood (can actually just send blood, dangerous to touch epiglottis = respiratory arrest)

54
Q

What is sinusitis?

A

Inflammation of the mucosal lining of the paranasal sinuses.
- pathogens enter from the upper respiratory tract into the normally sterile sinuses

55
Q

What is the basic anatomy of the sinuses?

A

Sinuses are lined with ciliated columnar epithelium, and are all connected with the sinus ostia which drain into different regions in the nasal cavity.

56
Q

What are some factors which may predispose to the development of sinusitis?

A
  • impaired mucocilliary function: cystic fibrosis, viral infections, allergic rhinitis
  • obstruction of the sinus ostia
  • immune defects
  • trauma
57
Q

Which microbial agents are likely to cause sinusitis?

A
  • Streptococcus Pneumoniae
  • Haemophilus Influenzae
  • Moraxella Catarrhalis
  • GAS
  • S. Aureus
  • Anaerobes
  • Rhino-
  • Influenza-
  • Parainfluenza
  • Adenoviruses
58
Q

What are the most important causative agents of sinusitis?

A

Streptococcus Pneumonia, rhino-, influenza-, parainfluenza-, adenoviruses

59
Q

What are the clinical manifestations of sinusitis?

A

Sinus pain, tenderness, purulent nasal discharge, headache, fever
(can’t distinguish clinically between bacterial and viral causes)

60
Q

What is the classification of Streptococcus Pneumoniae?

A

Gram-positive diplococci

61
Q

What is the classification of S. Aureus?

A

Gram-positive cocci in clusters

62
Q

How is the diagnosis of sinusitis made?

A
  1. Clinical (most NB)
  2. Imaging
  3. Antral puncture may be indicated in severe, unresponsive or recurrent disease
63
Q

How is sinusitis managed?

A

Medically (symptomatic management)

  • watch and wait
  • analgesics, intranasal steroids, saline nasal irrigation
  • in some cases surgical management is indicated
64
Q

Watching and waiting in acute sinusitis: why is is acceptable and what antibiotics should be used empirically?

A

Organisms of acute infection are predictable:

- for empiric antibiotic treatment: amoxicillin or amoxicillin-clavulanate

65
Q

What is done for the management of chronic sinusitis?

A

Often polymicrobial - can include anaerobes, gram negative bacilli or fungi
- Treat acute attacks!

66
Q

Why is surgery used in the management of sinusitis?

A

To restore sinus drainage

Respiratory Block: Microbiology (7 decks)

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