Streptococcus pneumoniae

Question 1

What makes pneumococcus Gram positive?

Answer 1

Peptidoglycan in cells walls

Question 2

Two components of peptidoglycan?

Answer 2

Alternating G,M,G,M

1. glucosamine
2. muramic acid

Question 3

How is pneumococcus identified? (Structural features on a culture)

Answer 3

1. gram positive

2. elongated cocci in pairs or chains

Question 4

Significance of polysaccharide capsule?

Answer 4

1. prevents neutrophil (PMN) from recognizing antibody that is attached to bacteria, unless antibody SPECIFICALLY recognies the capsule
2. best defense you can have to pneumococcus is an antibody that recognizes the capsule (either naturally acquired or via vaccine_
3. different polysaccharide capsules = way to differentiate between 93 types of pneumococcus

Question 5

Dissection of streptococcus pneumoniae name

Answer 5

streptococcus = genus
pneumoniae = species name

Question 6

What predisposes you to pneumococcus infection?

Answer 6

1. multifactorial (life extremeties, alcoholism, malnutrition)
2. decreased pulmonary clearance (lung disease, smoking, pollution)
3. DIMINISHED NEUTROPHIL FUNCTION (diabetes, cirrhosis, glucocorticosteroids)
4. defective IgG production
5. absence of spleen (doesn’t predispose you to infection but does increase risk of shock/sepsis)

Question 7

Most common cause of pneumonia in adults?

Answer 7

pneumococcus is most commonly identified bacteria!

Question 8

Clinical manifestations of pneumococcus (symptoms and signs)

Answer 8

1. OFTEN preceded by viral illness that goes on for several days
2. SOMETIMES sudden onset of shaking chill and fever
3. Cough, fever, sputum production, and chest pain (but sometimes harder to find in older patients)
4. general appearance (patients “looks sick” vs. viral harder to see symptoms)
5. abnormal chest exam (dullness to percussion, wheezes, rales)

Question 9

Proper way to diagnose pneumonia

Answer 9

CHEST X-RAY

Question 10

Common laboratory findings in pneumococcus infection

Answer 10

1. Higher WBC count = higher neutropihls

“left shift” - more band (immature) forms present

However, in OVERWHELMING infection, you will see a REDUCTION in WBC which has a bad prognosis

2. CHEST X-RAY - segmental, lobar, multilobar (viral)
3. low oxygen and pCO2 saturation

Question 11

Besides chest x-ray, how do you diagnose pneumococcus infection?

Answer 11

1. sputum
2. blood culture (bacteremia)
3. urine antigen test detects cell wall polysaccharide (specific)

Question 12

What other diseases to pneumococcus cause?

Answer 12

1. Acute otitis media
2. actue sinusitis
3. primary bacteremia - bacteria detected in blood with no apparent source called primary when no focus is recognized. Common cause of meningitis (esp when there’s no outbreak of meningococcal infection)
4. Lots of ITIS (septic arhtritis, osteomyelitis, peritonitis, cellulitis, endocaditis, pericarditas
5. acute cardiac event (23% of all patients)

Question 13

When you don’t have the antibody that recognizes the capsule, how do you defend against pneumococcal infection?

Answer 13

1. local (non-immunologic) - good patency of Eustachian tube and sinuses, ability to clear lower airways)
2. good general health (live stress free!)
3. innate immunity
4. humoral but not capsule related (i.e. an antibody that recognizes pneumolysin or other surface protein antigens)

Question 14

Significance of pneumolysin

Answer 14

stimulates inflammatory response and activated complement when recognized (IMPORTANT VIRULENCE FACTOR aka factor that produces disease). Produced by pneumococcus

Question 15

What is the adult vaccine for pneumococcus?

Answer 15

Pneumovax (intuitive huhhh???)…works via T-cell independent immune reaction

Question 16

Is Pneumovax preventative in children under 2? Why not?

Answer 16

No. Immature response to polysaccharide capsular material (but you can administer protein-conjugated vaccine to help with this)

Question 17

How do protein conjugated vaccines work?

Answer 17

Chemical conjugation of polysaccharide (attaching) to a protein to ALTER MODE OF PRESENTATION. Also, stimulates antibody in nasopharynx which will prevent colonization, which will help eliminate these serotypes from the population

Question 18

What kind of endotoxins does pneumococcus produce?

Answer 18

TRICK QUESTION BEEYATCH. NONE.

they do have peptidoglycan which is analagous to endotoxin though

Question 19

How do we acquire the bacterium?

Answer 19

Pretty much confined to human beings, lives normally in healthy individuals, initially acquired via close contact

Remember, pneumococcus can colonize host without causing disease (like many other bacteria that can potentially cause infections)

Question 20

During invasion, what constituent protrudes through capsule to interact with epithelial cell surface?

Answer 20

lipotichoic acid

Question 21

How does one develop pneumonia? (pathogenesis)

Answer 21

1. attachment in nasopharynx followed by proliferation
2. then, carried by secretions to a place where clearance is poor (due to obstruction of damage to clearance function like cilia) or via local invasion via lymphatics or blood (unusual in pneumococcus)

Question 22

Basic property of pneumococcal disease

Answer 22

organisms get where they don’t belong, clearance is damaged, they induce inflammation -> disease results. Much of the disease is inflammatory response

Question 23

Difference between inhalation and aspiration

Answer 23

inhalation - breathing in aerosolized organisms

aspiration - mouth contents bypass trachea, occurs during sleep.
MOST PNEUMOCOCCUS INFECTION CAUSED BY ASPIRATION