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Respiratory Infections 2 Flashcards

1
Q

Most common cause of sinusitis and otitis media

A

Strep pneumoniae

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2
Q

Streptococcus pneumoniae: Biology

A
  • Gram positive diplococcus
  • (lanceolate/flame-shaped) cocci in pairs
  • Polysaccharide capsule
  • α-hemolytic on Blood Agar
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3
Q

Biochemical tests for streptococcus pneumoniae

A
  • Optochin sensitive
  • Bile soluble
  • Positive Quellung reaction
    • Detects capsule
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4
Q

How to prevent streptococcus pneumoniae

A
  1. Pneumococcal Polysaccharide Vaccine (PPSV23) – Inactivated Vaccine
    • Pneumovax 23; - purified capsular antigens of 23 serotypes
  2. Pneumococcal Conjugate Vaccine – Conjugate Vaccine
    • Prevnar 13® - contains polysaccharide from 13 vaccine serotypes conjugated to a protein
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5
Q

Who should take PPSV23 vaccine

A

➢ Adults 65 years or older
➢ Age 2 through 64 years with medical conditions (asplenia)
➢ Adults 19 through 64 years who smoke cigarettes, COPD, CF

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6
Q

Who should take Pneumococcal Conjugate Vaccine

A

➢ Children younger than 2 and adults 65 years or older

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7
Q

Streptococcus pneumonia Pathogenesis part 1

A
  1. Initial infection
    • S. pneumoniae colonizes epithelium of oropharynx and secrete IgA protease.
    • S. pneumoniae can persist asymptomatically in heathy host as biofilm.
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8
Q

Strep pneumonia Pathogenesis part 2

A
  1. Virulence Activation
    Primary viral infection triggers inflammation;
    Immunological stress disrupts biofilm, inducing release of Pneumolysin (cytotoxin)
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9
Q

Strep pneumonia pathogenesis part 3

A
  1. Contribution of Host Immune response
    • Resident macrophages recognize GPC with TLR2, releasing TNFα and IL-8
    • Neutrophils are recruited*
    • Bacteria escape phagocytosis by capsule and can migrate
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10
Q

S pneumonia secretes IGA protease, what does it do

A

cleave mucosal IgA, contributing to persistent mucosal colonization.

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11
Q

S. Pneumoniae Pathogenesis: Biofilm. What’s the purpose of the biofilm

A

persistent colonization

Chronic biofilm is a risk factor for exacerbation in high-risk patients esp. COPD.

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12
Q

Properties of pneumolysin

A

Cytotoxic for respiratory epithelial and endothelial cells
Inhibits ciliated epithelial cell activity
Decreases PMN effectiveness & Causes inflammation

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13
Q

What role does t independent b1 cells of spleen play in regards to S. Pneumoniae Pathogenesis

A

T-Independent B1 cells of spleen play an important role to generate anti-Capsule IgM to activate complement for blood- stream infections

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14
Q

What is a major risk factor for bacteremia, sepsis and meningitis with encapsulated bacteria.

A

Asplenia

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15
Q

Clinical presentation of sinusitis

A

Viral UTRI < 7 days; thin clear discharge
Bacterial URTI > 7 days; thick yellow discharge

  • Fever
  • Nasal stuffiness and thick discharge
  • Bad breath or loss of smell
  • Fatigue
  • Headache
  • Pressure-like pain, pain behind the eyes, toothache, or tenderness of the face
  • Sore throat and postnasal drip
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16
Q

Clinical Presentation: Acute Otitis Media

A

Infection of middle ear

  • Fever
  • Neonates: Irritability, feeding difficulties
  • Ear pain, and/or ear tugging
  • Hearing loss, ear stuffiness
  • Immobility, inflammation, perforation and/or bulging of tympanic membrane
17
Q

Clinical Presentation: Chronic Otitis Media

A
  • Infection persists for more than 3 weeks
  • Ear pain
  • Hearing loss
  • Chronic draining in ear canal
  • Air/fluid accumulation
  • Perforation and/or bulging of tympanic membrane

MRSA is the Most Common Cause
Effusion and suppuration seen

18
Q

Haemophilus influenzae: Biology

A

Gram-negative Coccobacilli/pleomorphic
• Facultative anaerobe
• Fastidious

19
Q

Non-Typeable (NTHi): non encapsulated is associated with which diagnosis

A

Associated with sinusitis, otitis media, bronchopneumonia*

20
Q

Typeable: Haemophilus influenzae Type b (Hib) has a capsule. Describe the capsule

A

Capsule composed of Polyribosyl-ribitol Phosphate PRP

21
Q

How to prevent Haemophilus influenzae Type b (Hib)

A

Hib-PRP Conjugated Vaccine

22
Q

Typeable: Haemophilus influenzae Type b (Hib) is associated with which diagnoses

A

epiglottis, sepsis, meningitis

23
Q

What’s required for growth of Haemophilus influenzae and which agar does it grow on

A

Requires NAD & Hemin for growth

Chocolate agar

24
Q

Haemophilus influenzae: Pathogenesis

A

Haemophilus influenzae, all types
• Pili : attachment, undergoes antigenic variation
• Non-pilus adhesins
E.g., P-2 Outer Membrane Protein OMP; attaches to sialic acid-containing mucin oligosaccharides.
• Biofilm: persistent colonization (with Moraxella esp. COPD)
• IgA proteases: persistent mucosal colonization
• LOS (Lipo-OligoSaccharide): Lacks O-antigen, has endotoxic Lipid A activity.
Haemophilus influenzae, Hib only
• Capsule: Anti-phagocytic, immune evasion, important for invasive infections

25
Q

Some GRam negative cocci and GN-coccobacilli have

LOS Lipo-Oligo-Saccharide (missing O-antigen). Who are they

A
  • Haemophilus
  • Moraxella
  • Bordetella
  • Neisseria
26
Q

Clinical Presentation of Epiglottitis (Encapsulated Hib only)

A 
• Fever
• Sore throat
• Dysphagia
• Stridor, restlessness
• Hoarseness
• Muffled voice “hot
potato voice”
• Tripod position (Neck Hyperextended, Trunk forward)
Enlarged epiglottis: “Thumb Sign”
27
Q

Moraxella catarrhalis: Biology

A
  • Gram negative diplococcus
  • Oxidase positive, strict aerobe, non motile
  • Colonizes URT, particularly children
  • Most isolates produce β- lactamases, resistant to penicillin
  • Associated with sinusitis, otitis media, bronchopneumonia*
28
Q

What agar does Moraxella catarrhalis grow on and how does it look ?

A

Blood & Chocolate agar

Solid colonies that can be pushed like “Hockey puck”

29
Q

What pathogenic factors does Moraxella catarrhalis use

A
  • Biofilm: Adherence to respiratory epithelium
  • LOS: Induction of Inflammation
  • As a co-pathogen with Haemophilus

Image shows : A biofilm recovered from the middle ear that contained NTHI (pseudo- colored green) and M. catarrhalis (pseudo-colored magenta).
Imaged by scanning electron microscopy.

30
Q

Strep pneumoniae resistance mechanism

A

Altered PBP

31
Q

Haemophilus influenzae Resistance Mechanism

A

β-lactamase

32
Q

Moraxella catarrhalis Resistance Mechanism

A

β-lactamase

33
Q

Staph aureus (MRSA) Resistance Mechanism

A

β-lactamase + Altered PBP

34
Q

Prognosis for bacterial urti

A

▪ Good Prognosis
▪ Often requires antibiotics to fully resolve
▪ Complete recovery can be 2-4 weeks, though antibiotic treatment is mostly successful
▪ Complications include tympanic perforation, chronic sinusitis/OM, deafness, abscess formation, pneumonia, exacerbation of COPD, pneumococcus = sepsis, meningitis

35
Q

Prevention of bacterial urti

A

▪ Pneumococcal, Hib vaccines, esp. infants, high risk ▪ Antibiotic resistance is becoming more common
▪ Avoid night-bottle feeding of infants

HR- RHS (3 decks)

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