Streptococcus pneumoniae

Question 1

Classify S. pneumoniae:

Answer 1

Gram +
Strep = chains; Coccus = round
Non-typable (i.e. they lack Lancefield antigens)
Alpha-hemolytic 
Catalase negative
Inhibited by optochin and bile salts

Appear as “Lancet shaped diplococci”*

Question 2

What diseases does S. pneumoniae primarily cause?

Answer 2

1) Community-acquired pneumonia
2) Bacterial meningitis (except during epidemics, which Neisseria causes)
3) Otitis media in children and adults (H. influenza is second)
4) Acute purulent sinusitis (H. influenza is second)

Question 3

What other diseases can S. pneumonia cause, but isn’t the primary agent that causes it?

Answer 3

1) Sepsis (secondary from primary pneumonia/meningitis)
* *Can be primary cause in asplenic and/or immunocompromised pts

2) Endocarditis (very infrequent cause)

Question 4

There are 10 virulence factors (VF) of S. pneumoniae. Attempt to name them:

Answer 4

1) Polysaccharide capsule
2) Pneumolysin
3) Hyaluronidase
4) Neuraminidase
5) Pili
6) Lipoproteins
7) Peptidoglycan + Teichoic acid
8) Choline-binding proteins (CBPs)
9) Competence protein
10) Autolysic, LytA

Question 5

Which VF is the most important for S. pneumonia? It’s purpose?

Answer 5

Polysaccharide capsule.

Prevents phagocytosis

Question 6

What is a diagnostic test that uses the polysaccharide capsule to ID S. pneumonia?

Answer 6

Quellung reaction.

–anti-capsule antibodies bind to the bacteria, stabilizing the capsule (makes it appear to swell)

Question 7

This VF is a pore-forming toxin the binds to cholesterol in cell membranes, causing cell lysis:

Answer 7

Pneumolysin

**cell lysis attracts PMNs, T&B lymphocytes, and mediates TLR4 inflammation

Question 8

This VF is responsible for S. pneumonia being classified as alpha-hemolytic:

Answer 8

Pneumolysin

Question 9

This VF allows increased adhesion to epithelia cells:

Answer 9

Pili

Question 10

This VF allows increased spread into hyaluronic acid rich tissues:

Answer 10

Hyaluronidase

Question 11

This VF allows S. pneumonia to obtain DNA from its environment:

Answer 11

Competence protein

Question 12

This VF is a subtype of choline-binding proteins, important in cell wall remodeling during division and also for increased release of inflammatory contents from it’s own cell wall:

Answer 12

Autolysin, LytA

–if inactivated, S. pneumonia is much less virulent

Question 13

This VF can:

1) be hydrolytic, releasing inflammatory cell wall fragments
2) bind nasopharyngeal or lung epithelia
3) bing complement factor H

Which VF is this?

Answer 13

Choline-binding proteins (CBPs)

• -LytA is the hydrolytic enzyme
• -PsaA binds to nasopharyngeal/lung tissue
• -PspA and PspC bind complement factor H, preventing phagocytosis

Question 14

How is peptidoglycan + teichoic acid virulent?

Answer 14

They bind together, forming C-polysaccharide (CP)

–CP can bind to CRP, activating complement and increase inflammation

–CP can bind pathogen recognition receptors (PRR), causing cytokine release from macrophage

Question 15

This VF is a cell-surface molecule that assists in iron uptake:

Answer 15

Lipoproteins

Question 16

How is S. pneumonia transmitted?

Answer 16

Close contact in crowded areas

Question 17

Where on the body can you find S. pneumonia?

Who is more likely to carry it?

Answer 17

1) It has a niche in the human nasal cavity
2) 60% healthy kids, 30% healthy adults asymptomatically carry it.

–primary vector is children, then 65+ y/o adults

Question 18

When are you more likely to get a disease from S. pneumonia?

Answer 18

Midwinter

Question 19

What are the tell-tale signs of pneumonia from S. pneumoniae?

Answer 19

Signs/Symptoms: Cough, fatigue, fever, shaking chills, sweats, SOB, pleuritic chest pain, rust-colored sputum

Physical exam: Diminished respiratory excursion (i.e. light breathing, due to chest pain), increased RR, increased tactile fremitis, inspiratory crackles, infiltrates on CXR

Question 20

How do you diagnose pneumonia?

Answer 20

1) Sputum sample
- -sample should have little saliva, few epithelial cells
2) CXR

Question 21

How do you treat pneumonia? (Outpatient and Inpatient)

Answer 21

1) Outpatient: give them a macrolide and doxycycline, amoxicillin (+/- clavulonic acid), or quinolone
2) Inpatient: Macrolide + penicillin, ampicillin, or ceftriaxone

Question 22

As a general rule, you treat a person with pneumonia for 10-14 days. What is a possible complication from this?

Answer 22

1) Abx resistance

2) Clostridium difficile super-infection

Question 23

How does a person with S. pneumonia most commonly acquire meningitis as a disease?

Answer 23

Bacteremia from a pneumonia infection.

Question 24

Symptoms of meningitis?

Answer 24

HA, stiff neck, photophobia, seizures, coma, frontal bulge in infants above fontanel

Question 25

How do you diagnose meningitis?

Answer 25

Blood and CSF cultures

Question 26

Treatment for meningitis?

Answer 26

1) Vancomycin (#1 choice by doctors)

2) Ceftriaxone (if susceptible)

Question 27

How does a person get an otitis media infection?

Answer 27

Nasal colony travels through the eustachian tube into the middle ear.

Neuroaminidase is an important VF here

Question 28

How do you dx otitis media?

Answer 28

Look at the tympanic membrane for redness, swelling/bulging, and rupture.

Question 29

How do you tx otitis media?

Answer 29

1) Amoxicillin + clavulanic acid (Augmentin)

2) Ceftriaxone (if amoxicillin doesn’t work)

Question 30

How do you know sinusitis is a from a bacterial infection, like S. pneumonia?

Answer 30

Purulent discharge occurs.

Tx it like you would otitis media (amoxicillin + clavulonic acid, i.e. Augmentin)

Question 31

What are 4 predisposing risk factors to increase one’s chance of getting disease from S. pneumonia?

Answer 31

1) Asplenia (less clearance of encapsulated bugs)
2) Complement/antibody defects
3) Diabetes, chronic lung disease, CHF, alcohol abuse, (bad PMN’s)
4) Prior URI

Question 32

What can you give to ppl that have predisposing rick factors for infection from S. pneumonia?

Answer 32

1) Pneumovax: vaccine with 23 capsular polysaccharides from the 23 most common serotypes
2) Prevnar 13: 13 most common serotypes attached to attenuated diptheria toxin