Respiratory Infections 2 Flashcards
Most common cause of sinusitis and otitis media
Strep pneumoniae
Streptococcus pneumoniae: Biology
- Gram positive diplococcus
- (lanceolate/flame-shaped) cocci in pairs
- Polysaccharide capsule
- α-hemolytic on Blood Agar
Biochemical tests for streptococcus pneumoniae
- Optochin sensitive
- Bile soluble
- Positive Quellung reaction
- Detects capsule
How to prevent streptococcus pneumoniae
- Pneumococcal Polysaccharide Vaccine (PPSV23) – Inactivated Vaccine
• Pneumovax 23; - purified capsular antigens of 23 serotypes - Pneumococcal Conjugate Vaccine – Conjugate Vaccine
• Prevnar 13® - contains polysaccharide from 13 vaccine serotypes conjugated to a protein
Who should take PPSV23 vaccine
➢ Adults 65 years or older
➢ Age 2 through 64 years with medical conditions (asplenia)
➢ Adults 19 through 64 years who smoke cigarettes, COPD, CF
Who should take Pneumococcal Conjugate Vaccine
➢ Children younger than 2 and adults 65 years or older
Streptococcus pneumonia Pathogenesis part 1
- Initial infection
• S. pneumoniae colonizes epithelium of oropharynx and secrete IgA protease.
• S. pneumoniae can persist asymptomatically in heathy host as biofilm.
Strep pneumonia Pathogenesis part 2
- Virulence Activation
Primary viral infection triggers inflammation;
Immunological stress disrupts biofilm, inducing release of Pneumolysin (cytotoxin)
Strep pneumonia pathogenesis part 3
- 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
S pneumonia secretes IGA protease, what does it do
cleave mucosal IgA, contributing to persistent mucosal colonization.
S. Pneumoniae Pathogenesis: Biofilm. What’s the purpose of the biofilm
persistent colonization
Chronic biofilm is a risk factor for exacerbation in high-risk patients esp. COPD.
Properties of pneumolysin
Cytotoxic for respiratory epithelial and endothelial cells
Inhibits ciliated epithelial cell activity
Decreases PMN effectiveness & Causes inflammation
What role does t independent b1 cells of spleen play in regards to S. Pneumoniae Pathogenesis
T-Independent B1 cells of spleen play an important role to generate anti-Capsule IgM to activate complement for blood- stream infections
What is a major risk factor for bacteremia, sepsis and meningitis with encapsulated bacteria.
Asplenia
Clinical presentation of sinusitis
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
Clinical Presentation: Acute Otitis Media
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
Clinical Presentation: Chronic Otitis Media
- 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
Haemophilus influenzae: Biology
Gram-negative Coccobacilli/pleomorphic
• Facultative anaerobe
• Fastidious
Non-Typeable (NTHi): non encapsulated is associated with which diagnosis
Associated with sinusitis, otitis media, bronchopneumonia*
Typeable: Haemophilus influenzae Type b (Hib) has a capsule. Describe the capsule
Capsule composed of Polyribosyl-ribitol Phosphate PRP
How to prevent Haemophilus influenzae Type b (Hib)
Hib-PRP Conjugated Vaccine
Typeable: Haemophilus influenzae Type b (Hib) is associated with which diagnoses
epiglottis, sepsis, meningitis
What’s required for growth of Haemophilus influenzae and which agar does it grow on
Requires NAD & Hemin for growth
Chocolate agar
Haemophilus influenzae: Pathogenesis
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
