L60 – Upper Respiratory Tract Infections Flashcards Preview

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Flashcards in L60 – Upper Respiratory Tract Infections Deck (89):
1

Locations of upper respiratory tract infections?

Above larynx, tracheobronchial tube

Mainly in nasopharynx and larynx

 Includes structures connected to nasopharynx: perinasal sinus,
middle ear, eye

2

What are some underlying conditions/ diseases that can lead to/ exacerbate URT infection?

 Systemic diseases
 Respiratory diseases
 Drugs

3

How does age relate to the type of URTI?

young: viral
elderly: bacteria

4

How does time of year relate to URTI?

seasonality pattern:

e.g. influenza – 1 peak in summer, winter

5

What are some innate defense mechanisms in the Nasopharynx?

- Nasal hairs
- Turbinates (bone in nose covered by moucosa)
- Mucociliary apparatus
- Secretory immunoglobulin A (sIgA) secretion

6

What are some innate defense mechanisms in the Oropharynx?

 Saliva
 Sloughing of epithelial cells (layer of skin comes off)
 pH
 Bacterial interference
 Complement production

7

What are some innate defense mechanisms in the Trachea and bronchi?

 Cough, epiglottic reflexes
 Sharp-angled branching of airways
 Mucociliary apparatus
 Ig production (IgG, IgM, IgA)

8

How does sharp-angled branching of airways protect the respiratory tract from infections?

 ↑ surface area for gas exchange

 Particles >5μm knock on bifurcation = trapped in mucous and phagocytosed

 Particles <5μm: not filtered and can reach most distal terminal

9

What are some innate defense mechanisms in the Terminal airways and alveoli?

 Alveolar lining fluid
 Alveolar macrophages
 Neutrophils
 Cell-mediated immunity

10

What is the general assessment for URTI?

- Age
- Time of year
- Site of infection
- Clinical syndrome
- Underlying immune impairment/ diseases if any

11

Are antibiotics used to treat MOST cases of pharyngitis?

Viral
Dont use antibiotics

12

What is the incubation period of Group A streptococcal pharyngitis? What is the usual time before subside?

2-4 days

Usually subside in ~1 week

13

What is the transmission of Group A streptococcal pharyngitis? Is it always symptomatic?

Direct person-to-person contact

 Facilitated by over-crowding
 Can have asymptomatic carriage

14

How are the acute onset symptoms for Group A strep. pharyngitis?

Sore throat
Malaise
Fever
Headache

15

What are the manifestations of Group A strep. pharyngitis on lymphoid organs and tonsils?

 Redness, lymphoid hyperplasia of posterior pharynx

 Hyperaemic tonsils + greyish white exudate

 Tender lymph nodes (sensitive to pain)

16

What is the treatment of choice for Group A Strep. Pharyngitis?

Penicillin

17

Compare between viral and Streptococcal pharyngitis:
Onset?

Strep = Abrupt
Viral = Gradual

18

Compare between viral and Streptococcal pharyngitis: Throat pain?

Strep= Painful
Viral= Uncomfortable

19

Compare between viral and Streptococcal pharyngitis: Cervical nodes?

Strep= Enlarged, tender
Viral= Not enlarged

20

Compare between viral and Streptococcal pharyngitis: Eyes and nose?

Strep= not affected
Viral= watery eyes + runny nose

21

Compare between viral and Streptococcal pharyngitis: Throat and tonsils?

Strep= Red, swollen, exudates
Viral= Red, vesicles, ulcers

22

What is the most definitive way to differentiate between viral and streptococcal pharyngitis?

1) Gold standard = throat swab >> bacteriological culture

2) Antigen detection tests for Strep. A antigen (e.g. put swab in commercial kit)

If culture and antigen detection for bacteria returns negative, then the infection must be viral

23

What are the 2 types of Streptococcal pharyngitis complications?

Suppurative (pus) and Non-suppurative (no pus)

24

Name some suppurative complications of Strep. A pharyngitis?

- Local abscess
- Pneumonia
- Bacteraemia with metastatic foci of infection
- Intracranial infections

25

What types of Local abscesses can form in suppurative complications of Strep. A pharyngitis?

abscesses:

retropharyngeal, parapharyngeal,
peritonsillar

>> all cause swollen sneck and obstruct airway

26

What types of intracranial infection can form in suppurative complications of Strep. A pharyngitis?

Acute otitis media in middle ear

Acute sinusitis in nose

27

What are the 2 Non- suppurative/ immunological complications of Strep. A pharyngitis?

Acute rheumatic fever

Post-streptococcal glomerulonephritis (PSGN)

(+ arthritis)

28

What criteria is used to diagnose Acute rheumatic fever?

Jones criteria

29

Recurrent attacks of acute rheumatic fever can lead to what?

Recurrent valvular damage > Chronic rheumatic heart disease > infective endocarditis

30

How does Strep. A bacteria cause acute rheumatic fever and evade host defense?

result of molecular mimicry:

heartreactive antibodies (HRA) cross-reacts with:

a) antigens on heart tissues
b) group A streptococcal antigens

>> body attack own tissue
similar mechanism in PSGN

31

What drugs are used as prophylaxis for recurrent attacks of acute rheumatic fever?

IM benzathine penicillin,
oral penicillin V,
erythromycin,
sulphonamides

32

What drugs are used as prophylaxis for infective endocarditis?

 Oral amoxicillin (high dose)
 IV ampicillin + gentamicin

33

What is the gram stain, hemolysis and morphology of Strep. pyogenes?

gram-positive, beta-hemolytic, in chains

34

What is the gram stain, sprouting, motility and morphology of Corynebacterium diphtheriae?

Gram-positive bacillus,
non-sporulating, non-motile,
unencapsulate

35

What does Corynebacterium diphtheriae cause?

Diphtheria

36

What is the primary prophylaxis of Diphtheria?

vaccination with diphtheria toxoid
Good childhood immunization coverage

37

What are the 2 types of Diphtheria?

Cutaneous diphtheria
Oropharynx diphtheria

38

What are the unique, differentiating histological factors of Corynebacterium diphtheriae ?

1. ‘Chinese character’ palisades
2. Metachromatic granules

39

What are the 2 cultures of Corynebacterium diphtherniae? Which one is selective and which one isnt?

 Loeffler medium (non-selective)
 Potassium tellurite medium/ Hoyle's medium (selective)

40

What is the positive result for Corynebacterium diphtherniae in Hoyle's/ Potassium tellurite medium?

Potassium tellurite medium

>> gun-metal black / dark grey colonies

41

What are the transmission routes for Corynebacterium diphtheriae? Is it always symptomatic?

Droplet transmission:
 Direct contact with respiratory secretions
 Asymptomatic carrier state exists

42

Diphtheria is a endotoxin or exotoxin mediated disease? What does the bacteriophage carry?

Exotoxin

Bacteriophage carries tox gene

43

What is the action of C. diphtheriae exotoxins?

Diphtheria exotoxin inactivates elongation factor 2 (EF2)

inhibits protein synthesis > cause respiratory disease, systemic effect, cutaneous diphtheria

44

What respiratory disease is caused by C. diphtheriae?

sore throat >> inflamed, necrotic epithelium

form pseudomembrane (‘white throat’) and obstruct airway)

45

What systemic effects are caused by C. diphtheriae?

fever, myocardial depression, neuropathy

46

What is the manifestation of cutaneous diphtheria? Which social groups are most affected?

 Typically manifests as chronic non-healing skin ulcers

 Especially among the underprivileged

47

What are the treatment options for diphtheria?

 Diphtheria antitoxin
 Penicillin, erythromycin
 Supportive care

48

Describe acute epiglottitis?

rapidly progressive cellulitis of epiglottis, adjacent structures

49

What is the classical and alternative cause of acute epiglottitis?

Classical = Haemophilus influenzae type b

Alternative:
 Beta-haemolytic streptococci (S. pneumoniae, S. pyogenes)
 Staphylococcus aureus
 Klebsiella pneumoniae

50

How does age relate to the cause of acute epiglottitis?

Bhildren (2-4 yrs old) most commonly affected

Classical cause of Haemophilus influenzae type b affects CHILDREN

Alternative causes (e.g. Strep. aureus) affect ADULTS

51

What are some causes of non-infectious epiglottitis?

trauma, irradiation, caustic ingestion, inhalational injury

52

What are the rapid onset symptoms of acute epiglottitis?

 Fever
 Irritability
 Dysphonia = cannot speak
 Dysphagia = drooling of saliva
 Sore throat
 Respiratory distress

53

Why is acute epiglottitis a medical emergency?

Swelling can suddenly lead to complete airway obstruction > respiratory distress and death

* hence acute epiglottitis is a medical emergency *

54

What is the procedure that follows clinical suspicion of acute epiglottitis? What precaution is taken?

Examine epiglottis only when immediate intubation is possible

may cause laryngeal spasm and airway obstruction >> may need to perform tracheostomy

55

What clinical confirmatory tests can be done to confirm acute epiglottitis?

 Laryngoscopy: cherry-red epiglottis
 Lateral neck X ray: thumb sign, narrowing of pharynx

56

What are the empirical antibiotics of choice for acute epiglottitis?

3rd generation cephalosporins
(e.g. ceftriaxone, cefotaxime)

57

What are the 4 paired paranasal air sinuses?

Frontal - lower forehead
Maxillary - cheekbones
Ethmoid cells - beside upper nose
Sphenoid - behind nose

58

What is the normal sterility and secretion drainage of the paranasal air sinuses?

 Normally sterile
 Secretion normally drains into osteomeatal complex

59

What are the common and alternatice predisposing factors/ antecedent conditions for acute sinusitis?

Most common = Upper respiratory tract viral infection

Other factors = allergy, dental root infection of maxillary sinusitis (rare)

60

Explain the pathogenesis of acute sinusitis?

swelling of inflamed mucosal lining in nasopharynx (e.g. URTI, allergy)

>> obstruct / impair normal sinus drainage into osteomeatal complex

>> abnormal buildup of fluid in sinus + bacteria infection

61

What are the 4 categories of sinusitis?

1. Acute community acquired sinusitis
2. Chronic sinusitis
3. Nosocomial (hospital-acquired) sinusitis
4. Fungal sinusitis

62

In Acute community-acquired sinusitis, what are the common pathogens?

Bacteria (90%)
Respiratory virus (10%)

*sterile cultures in 25%*

63

Name the bacteria that causes Acute community-acquired sinusitis?

1. Streptococcus pneumoniae (~40%) (most common)

2. Haemophilus influenzae (~30%)

3. Moraxella catarrhalis (~20% in children)

64

Name the viruses that causes Acute community-acquired sinusitis?

-rhinovirus,
-parainfluenza virus,
-adenovirus,
-influenza virus

65

What are the clinical features of acute sinusitis? (persistent and severe symptoms after URTI)

Fever,
Facial Pain
Headache
Purulent nasal and postnasal discharges

66

What are the 3 categories of complications of acute sinusitis?

 Intra-orbitally
 Intracranially
 Peri- orbital (can affect eyes)

67

What are the Intracranial complications of acute sinusitis?

 Brain abscess, meningitis
 Osteomyelitis of frontal bone:
- in frontal bone or ethmoid sinus

68

Apart from clinical symptomatology, physical examination, what 2 other procedures are done for clinical diagnosis of acute sinusitis?

Imaging: sinus X-ray and CT scans

Culture: sinus puncture and aspiration of sinus in complicated cases
*not routinely needed*

69

Is normal culture of nasal discharge used for diagnosis of acute sinusitis?

Culture of nasal pus / sinus exudates: not reliable

70

What is seen in the X rays and CT scans for acute sinusitis?

 Sinus X rays: opaque = sinusitis


 CT scan:
Normally air-filled = black; Fluid-filled = white
*CT is sensitive in picking up lesions in sinus*

71

What is the empirical antibiotic treatment for acute sinusitis?

Empirical antibiotic coverage against:
Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis

72

What drugs are used for acute sinusitis?

ampicillin-sulbactam, amoxicillin-clavulanate, cefuroxime

**need to Consider local pattern of antibiotic resistance**

73

When is surgery used to treat acute sinusitis? (think of the types of sinusitis that needs surgery)

-Severe / chronic sinusitis

-suspected intra-orbital / intracranial involvement

> surgery is used to drain sinus

74

Acute otitis media affects what age group of the population most?

primarily a disease of childhood

(peak incidence: 6-24 months)

75

What are some anatomical features that predisposes acute otitis media?

Anatomical defects:

-cleft palate, cleft uvula
-physiological abnormalities of Eustachian tube

76

How does the structure of the Eustachian tube predispose acute otitis media? (Pathogenesis)

obstruct normal drainage of
Eustachian tube:

fluids, secretions accumulate in middle ear (cannot drain to nasopharynx)

> increase risk of infection

77

Apart from anatomical defects and physiological abnormalities, what are the 2 other predisposing factors for acute otitis media?

-preceding viral upper respiratory tract infection: potential bacterial pathogens colonize nasopharynx


-Congenital / acquired immunodeficiencies

78

Acute otitis media is usually preceded by what?

Viral URTI

37% of URTI leads to acute otitis media

79

What bacteria commonly causes acute otitis media? (same bacteria as acute sinusitis)

 Streptococcus pneumoniae (20–30%)

 Haemophilus influenzae (25–35%) (most common)

 Moraxella catarrhalis

80

What are some uncommon pathogens causing acute otitis media?

 Streptococcus pyogenes (2–4%)
 Staphylococcus aureus
 Viruses

81

What are some general and ear-related symptoms of acute otitis media?

General:
-Fever
-Lethargy
-Irritability

Ear:
- Ear pain
- Erythema of tympanic membrane (eardrum)
- Perforation > Ear drainage (e.g. pus)
- Hearing loss (e.g. unilateral)

82

How is erythema of trympanic membrane caused in acute otitis media?

Fluid accumulation in middle ear> pressure increases > erythemia of tympanic membrane > bulging with pus

83

What are some complications of acute otitis media?

intracranial spread to brain, mastoid complex

84

What is the empirical antibiotic coverage for acute otitis media?

Same as acute sinusitis:

-amoxicillin
-amoxicillin-clavulanate
-cefuroxime

85

What special consideration is given to neonates / immunosuppressed individuals with acute otitis media?

consider infection due to more resistant / unusual organisms

86

When is culture needed for acute otitis media? Is it normally needed?

Normally not needed

**Tympanocentesis > aspiration of the middle ear content

Only use if patient is critically ill, unresponsive to antibiotics, immunocompromised

87

Where is infection in otitis externa?

External auditory meatus

88

What are the pathogens that cause otitis externa?

 Staphylococcus aureus >> acute localized

 Pseudomonas aeruginosa >> malignant

89

What are the treatment options for otitis externa?

 Systemic antibiotics

 If necessary: surgical drainage of abscess,

debridement (remove damaged tissue)

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