Streptococcus pneumoniae Flashcards
What is the gram classification of S. pneumoniae?
Gram-positive coccus
What’s usually the microscopic appearence of S. pneumoniae?
Lancet-shaped diplococcus
Is S. pneumoniae catalase-positive or negative?
Catalase-negative
How does S. pneumoniae generate H2O2?
Via flavoenzyme system
S. pneumoniae grows better in the presence of…
Catalase sources
Which toxin does S. pneumoniae produce that causes α-hemolysis (partial hemolysis)?
Pneumolysin
What is the effect of pneumolysin on hemoglobin?
It breaks down hemoglobin
Which laboratory tests are used to identify S. pneumoniae?
- α-hemolysis on blood agar (positive)
- Susceptibility to optochin (susceptible)
- Solubility in bile salts (soluble)
What is the significance of optochin susceptibility in S. pneumoniae?
Most strains are optochin suceptible
What diseases can S. pneumoniae cause?
- COPD exacerbation
- Pneumonia
- Meningitis
- Sinusitis
What are the definitive identification methods for S. pneumoniae?
- Bile solubility test
- Commercial DNA probes for rRNA genes
What are the main components of S. pneumoniae’s cell wall?
Peptidoglycan and teichoic acid
This polyssacharide is found in all pneumococci.
C-polyssacharide
Which acute-phase reactant reacts with C-polysaccharide during inflammation?
CRP
This group of proteins Help S. pneumoniae attach to mucosal surfaces.
Choline-binding proteins.
What are the choline-binding proteins (CBPs) in S. pneumoniae?
- Pneumococcal surface proteins A and C (PspA, PspC)
- Surface adhesins (CbpA, CbpC)
T/F. PspC and CbpA are the same protein.
True
Lol
This CBP inhibits C3b, preventing opsonization.
PspA
This CBP binds H factor, blocking complement-mediated killing.
PspC (CbpA)
What is the role of CbpC in S. pneumoniae?
Involved in DNA uptake (assists)
What antibody can S. pneumoniae cleave using a protease?
IgA
What structure is present in nearly all clinical isolates of S. pneumoniae?
Polyssacharide capsule
T/F. Encapsulated pneumococci are more virulent.
True
Where does capsule synthesis occur in S. pneumoniae?
In the cytoplasm
How do pneumococci acquire new genetic material?
Via transformation
What protein allows DNA uptake in S. pneumoniae?
Competence-sensing protein
What is the range of disease caused by S. pneumoniae?
- Asymptomatic colonization
- Mucosal disease (otitis media, sinusitis, pneumonia)
- Invasive infections
What is the most common clinical manifestation of S. pneumoniae?
Otitis media
Which pneumococcal disease has the greatest impact on morbidity and mortality?
Pneumococcal pneumonia
Why are infants <6 months relatively spared from pneumococcal disease?
- Maternal transfer of IgG (placenta)
- Mucosal IgA (breast milk)
When does the risk of pneumococcal disease increase in infants?
After 6 months, as passive immunity declines
Which conditions increase hospitalization risk for pneumococcal pneumonia in older adults?
Diabetes and organ dysfunction
How is S. pneumoniae spread?
Close contact
Which environments pose a high risk for pneumococcal transmission among toddlers?
Daycare centers
When does pneumococcal disease peak?
Winter
What environmental factors may facilitate pneumococcal disease transmission?
Colder temperatures and low humidity
What are the methods used to detect pneumococcal colonization?
- Culture
- High-throughput sequencing
- PCR
Which demographic and environmental factors increase the risk of pneumococcal colonization?
- Living in resource-limited countries
- Presence of siblings at home
- Crowded living conditions
- Lower socioeconomic status
What exposure-related factors contribute to pneumococcal colonization?
- Smoke exposure
- Antibiotic use
- Respiratory viral infections
What are the key bacterial factors that facilitate pneumococcal adherence?
- Neuraminidase A and B
- PspA
What is the function of neuraminidase A and B?
Expose N-acetylglucosamine receptors on epithelial cells
How does pneumococcal PspA contribute to adherence?
It binds to exposed N-acetylglucosamine receptors on epithelial cells
Which immune components are crucial for defense against S. pneumoniae?
Antibodies, complement, and phagocytes (especially neutrophils)
Which complement deficiency is most strongly associated with recurrent pneumococcal infections?
C3 defficiency
How does mannose-binding protein (MBP) deficiency affect pneumococcal susceptibility?
Increases risk of bacteremia
What factors increase pneumococcal susceptibility in older adults?
- Weakening of gag/cough reflexes
- Malnutrition
- Organ dysfunction
Which sites are affected by direct spread from the nasopharynx?
Middle ear, sinuses, trachea, bronchi, and lungs
How is otitis media diagnosed?
Based on visualization of the tympanic membrane
T/F. S. pneumoniae is the most prevalent oathogen in otitis media in adults.
True
Obstruction of sinus orifices due to viralinfection, pollutants, or allergens, leads to fluid accumulation in paranasal sinus cavities and can cause…
Sinusitis
What often triggers lower respiratory infections?
Aspiration of oropharyngeal bacteria
T/F. S. pneumonia doesn’t cause a severe pneumonia.
False; its the most virulent bacterial cause
What causes consolidation to appear on radiographs in pneumococcal pneumonia?
Filling of alveoli with microorganisms and exudate
What are the most common symptoms of pneumococcal pneumonia?
- Cough
- Fatigue
- Shortness of breath
- Dyspnea
- Fever
- Chills
- Sweats
- Purulent sputum
- Pleuritic chest pain
What’s the current treatment for pneumococcal otitis media if the bacteria is not resistant?
Amoxicilin-clavulanate
If S. pneumoniae is penicillin-resistant, what´s the best treatment?
Cephalosporins
First line therapy for pneumococcal sinusitis.
Amoxicillin ± clavulanate
Which antibiotics are effective for pneumonia caused by S. pneumoniae?
- Penicillins ± β-lactamase inhibitors
- Macrolides
- Doxycycline
- Quinolones (not in children)
Microscopic test used to detect the capsule of encapsulated bacteria, most commonly Streptococcus pneumoniae.
Quellung reaction
What’s S. pneumoniae’s vaccine directed to?
The capsule
