Strep Pneumo

Question 1

Which organism causes the majority of the cases of bacterial pneumonia, leading to hospitalization?

Answer 1

-Strep Pneumoniae

Question 2

Is strep pneumoniae gram positive or negative?

Answer 2

Gram + (Blurple)

Question 3

What is alpha hemolysis?

Answer 3

-when grown on agar that contains RBC’s, a molecule called alpha-hemolysin breaks hemoglobin down to a greenish pigment

Question 4

What is the outermost layer of pneumococcus?

Answer 4

• a polysaccharide capsule
• contains peptidoglycan

Question 5

What does PMN stand for?

Answer 5

-polymorphonuclear Leukocytes

Question 6

Why is pneumococcus not readily ingested by PMNs?

Answer 6

• The capsule is not recognized by receptors on PMN
• in the absence of antibodies to specific capsular polysaccharide, they won’t be eaten by PMN
• IgG to cell wall can’t be “seen” by PMN

Question 7

Why are antibodies for the cell wall of pneumococcus not immune response inducing?

Answer 7

-The capsular polysaccharides are too long, and shield the Fc region of abs from PMNs

**Ig and complement diffuse through capsule, but capsule prevents PMN receptors from interacting with Fc of IgG.

Question 8

What are the constituents of pneumococcus from the outside going in?

Answer 8

• Polysaccharide capsule
• Teichoic acid attached to lipid (lipoteichoic acid)
• Choline-Binding Proteins
• Peptidoglycan: Principal constiduent of cell wall
• Pneumolysin
• Autolysin

Question 9

What factors cause decreased neutrophil function (chemotaxis, ingestion, killing)?

Answer 9

• Diabetes Mellitus
• Glucocorticosteroids
• Renal insuficiency
• Cirrhosis
• Alcohol Ingestion
• Genetic defects in PMN function

Question 10

What factors can lead to defective IgG production?

Answer 10

• Congenital
• Acquired: myeloma, lymphoma, common variable immunodeficiency
• HIV infection

Question 11

How are splenectomies related to pneumococcal pneumonia?

Answer 11

-doesn’t predispose to infection

***but does predispose to overwhelming sepsis and shock in pneumococcal pneumonia

Question 12

What is pneumolysin?

Answer 12

• a major virulence factor produced by pneumococci
• activates complement (inflammation)
• Damages ciliated cells and PMN
• reproduces changes of pneumonia in animals

Question 13

What is the difference between epidemiology & pathogenesis?

Answer 13

Epidemiology = where the organism likes to hang out

Pathogenesis = how disease comes about

Question 14

How is pneumococcal pathogenesis related to viral illness?

Answer 14

• viral infection characterizes the major form of pneumococcal disease
• virus messes up our normal anatomy (cilia), and pneumococcus gets stuck where its not supposed to be

Question 15

Describe the microbiology of pneumococcus.

Answer 15

• pairs or chains of elongated cocci
• gram positive
• colonies on blood agar surrounded by greenish zone (alpha-hemolysis)
• colonies collapse in center (autolysin)
• optochin susceptibility (ring of death around white thing)
• dissolve in bile salts (definitive identification)

Question 16

Which TLR does Teichoic acid of pneumococcus interact with ?

Answer 16

TLR 2 >>4

Question 17

What is important about Choline-binding proteins on pneumococcus?

Answer 17

• they contribute to virulence
• highly conserved between pneumococci strains

Question 18

What are bacterial cell wall peptidoglycans made of?

Answer 18

-alternating glucosamine and muramic acid in long chains

Question 19

Which TLR recognizes cell wall peptidoglycans?

Answer 19

TLR 2 >> 4

Question 20

What is the epidemiology of pneumococcus?

Answer 20

• Confined to humans
• lives in nasopharynx of healthy children/adults
• contact or aerosol spread (facilitated by viral resp infection)

Question 21

What must first happen for bacteria to cause disease?

Answer 21

• adhere to epithelial cells
• bacterial surface constituents interact with surface molecules on mammalian cells, causing adherence

Question 22

What molecule on pneumococcus is responsible for adherence?

Answer 22

-Lipoteichoic acid

Question 23

What is colonization?

Answer 23

-when bacteria are present in sufficient number that we can find them by culture, AND, they cause no symptoms or signs of infection

**some organisms never colonize, mere presence indicates infection (TB)

Question 24

What is the pathogenesis of pneumococcus?

Answer 24

• carried by secretions to space from which clearance is poor (damage/obstruction)
• aspiration & inhalation = pneumonia

**organisms get where they do not belong, clearance is damaged, induce inflammation & disease results.

Question 25

What is the difference between inhalation and aspiration of an organism?

Answer 25

- **inhalation** = breathing in aerosolized organisms - **aspiration** = mouth contents bypass glottis

Question 26

What factors decrease action of cilia and cough in the respiratory tract?

Answer 26

- Smoking - inflammation - viral infection - Alcohol, codeine, morphine (suppress cough) - pollution

Question 27

How does pneumonia result from pneumococcus infection?

Answer 27

- cocci reach alveoli, activating inflammatory response - WBCs attracted & capillary permeability increased - this means WPCs, plasma constituents, and RBC's collect in alveoli = **pneumonia infiltrate**

Question 28

What factors predispose people to infection by pneumococcus?

Answer 28

- Multifactorial: extremes of life, prior hospitalization, malnutrition, alcoholism - Decreased pulmonary clearance - diminished neutrophil function - defective IgG production - absence of spleen

Question 29

What are the common clinical manifestations of pneumonia?

Answer 29

(often preceded by viral infection) - Cough (90%) - Fever (90+%) - sputum production (variable) - chest pain (50-75%) - general appearance = **look sick** - can percuss and listen for rales, but xray is best

Question 30

What are the lab findings for pneumonia?

Answer 30

-High WBC, possible left shift \*\*reduction in WBC = overwhelming infection - opacity in chest xray - decreased O2 sat

Question 31

How is the diagnosis for pneumonia made?

Answer 31

- gram stained sputum (90%) - Blood culture (bacteremia) (20%) - Urine antigen test (50%) = highly specific

Question 32

What other diseases are commonly caused by pneumococcus?

Answer 32

- Acute otitis media - acute sinusitis - primary bacteremia - meningitis - acute cardiac events (23%)

Question 33

What are the vaccine options for pneumococcus?

Answer 33

- Pneumovax (adult) - Protein-conjugated vaccine (children)

Question 34

How does the pneumovax vaccine work?

Answer 34

-contains capsular polysaccharide of 23 pneumococci serotypes \*\*not protective before age of 2 years, due to immature immune response to polysaccharides

Question 35

how does the protein-conjugated vaccine for pneumococcus work?

Answer 35

- chemical conjugation of polysaccharide to a protein that alters the mode of presentation, so it works in babies - stimulates antibody in nasopharynx, thus preventing colonization

Question 36

What are the three main bacterial causes of acute otitis media?

Answer 36

1. Strep pneumo (30%) 2. H. influenzae (25%) 3. Moraxella catarrhalis (15-20%)