Streptococcus pneumoniae characteristics

Question 1

Defence mechanisms of the upper respiratory tract
1)
2)
3)
4)

Answer 1

1) Nose hairs, tubinates
2) Epiglottis and cough reflex
3) Ciliated respiratory surface of URT, covered with mucus secreting lysozyme, lactoferrin, sIgA
4) Mucocilliary elevator

Question 2

Defence mechanisms of the lower respiratory tract
1)
2)
3)

Answer 2

1) Alveoli contain sIgA, surfactant proteins, alveolar macrophages
2) Well-developed blood supply allows neutrophil, leukocyte, macrophage
3) Abundant MALT, systemic lymphoid tissue

Question 3

Predisposing factors to LRT infection
1)
2)
3)

Answer 3

1) Defect in innate defences, EG: cilia
2) Can occur with influenza infection, smoking, immobility, anaesthetisation, heavy drinking
Immunosuppression, extremes of age, poor nutrition
3)No spleen

Question 4

Difference in microbiome between URT and LRT

Answer 4

URT - Predominantly G+ cocci

LRT - Very few to no organisms

Question 5

Pneumonia

Answer 5

Acute inflammation of the lungs

Question 6

Symptoms of pneumonia
1)
2)
3)
4)
5)
6)
7)

Answer 6

1) Cough
2) Fever
3) Chest pain
4) Shortness of breath
5) Rapid respiration
6) Cyanosis
7) Chest sounds

Question 7

Type of pneumonia caused by S. pneumoniae

Answer 7

Lobar pneumonia

Question 8

Prevalence of asymptomatic S. pneumoniae infection

Answer 8

~60% children carry it

Lower proportion of adults

Question 9

More common cause of disease in URT

Answer 9

Viral

Question 10

More common cause of disease in LRT

Answer 10

Bacterial

Question 11

Nose turbinates

Answer 11

Bone structures with mucus layer in nose
Warm, humidify air passing through nose
Mucus filters microbes, dust, pollen, etc
Three turbinates on each lateral nostril

Question 12

Role of spleen in bacterial infection

Answer 12

Removed capsulated bacteria

Question 13

Antibody types directed against capsular bacteria

Answer 13

IgG, IgM

Question 14

Difficulty in analyzing sputum sample

Answer 14

Sputum coughed up through the mouth –>
Contaminated with normal flora in mouth
Squamous epithelial cells in sample imply contamination from mouth

Question 15

Diseases caused by S pneumoniae
1)
2)
3)

Answer 15

1) Otitis media
2) Bacterial meningitis
3) Pneumonia

Question 16

Type of hemolysis caused by S pneumoniae

Answer 16

Greening

Don’t completely lyse red cells

Question 17

Anti microbial used to test for S pneumoniae

Answer 17

Optochin

Question 18

Lab diagnosis of S pneumoniae
1)
2)
3)
4)

Answer 18

1) Gram positive
2) Alpha haemolytic on horse blood agar
3) Optochin resistant
4) Capsule stain

Question 19

Chance of comorbidity with strep pneumoniae

Answer 19

50% of people with streptococcal pneumonia have an underlying condition

Question 20

Non-invasive S pneumoniae infections
1)
2)
3)
4)

Answer 20

1) Otitis media
2) Conjunctivitis
3) Sinusitis
4) Pneumonia

Question 21

Invasive S pneumoniae infections
1)
2)
3)
4)
5)

Answer 21

1) Septicaemia
2) Endocarditis
3) Septic arthritis
4) Peritonitis
5) Meningitis

Question 22

Catalase of S pneumoniae

Answer 22

Negative

Question 23

Metabolism of S pneumoniae

Answer 23

Facultative anaerobe

Question 24

Role of optochin disc in testing for S pneumoniae

Answer 24

Differentiates between pneumoniae and other alpha-haemolytic streptococci of the oral cavity that aren’t associated with LRT infection

Question 25

Appearance of S pneumoniae colonies on HBA

Answer 25

Mucoid colonies, greening haemolysis

Question 26

Number of S pneumoniae capsular antigen types

Answer 26

91

Question 27

Is S pneumoniae extra- or intracellular?

Answer 27

Extracellular

Question 28

Pyogenic

Answer 28

Phagocyte-avoiding, therefore pus-forming

Question 29

Specificity of antibodies produced against capsule

Answer 29

Very specific

Little cross-reaction

Question 30

S pneumoniae NET evasion mechanisms

Answer 30

DNAases break down neutrophil extracellular traps

Question 31

Pathogenesis of S pneumoniae

Answer 31

1) Releases hydrogen peroxide
2) Pneumolysin release
3) Autolysin release
4) Inflammation caused by PRR and complement interactions

Question 32

Reason for S pneumoniae being catalase negative

Answer 32

Releases H2O2

Would degrade this if it were catalase positive

Question 33

Pneumolysin

Answer 33

Released by S pneumoniae in later phase of growth

Triggers the complement cascade (pro-inflammatory)

Forms pores in the membranes of cells with cholesterol in cell membrane (alveolar, endothelial cells)

Question 34

Autolysins

Answer 34

Released by bacteria in stationary phase
Initiate bacterial death
Bacterial death leads to cell-wall component release that triggers complement cascade

Question 35

Major component of damage from S pneumoniae infection

Answer 35

Inflammatory response

Question 36

How does S pneumoniae induce the inflammatory response?
1)
2)

Answer 36

1) Autolyins activate complement

2) C reactive protein binds phosphoryl choline residues on damaged or dying cells –> activates complement cascade

Question 37

Steps in inflammatory response to S pneumoniae
1)
2)
3)
4)

Answer 37

1) Endothelial activation leads to fluid influx
2) Neutrophils enter, but bacteria resist phagocytosis
3) Large numbers of neutrophils enter, fever and impaired lung function because of excessive cytokine release
4) Resolution, macrophages scavenge debris

Question 38

Local complication of S pneumoniae infection

Answer 38

Pleural effusion

Question 39

Systems that resolve S pneumoniae infection

Answer 39

Complement

Antibodies

Question 40

Supportive treatment for S pneumoniae infection

Answer 40

Bronchodilators, oxygen, analgesics

Question 41

Antimicrobial agents used against S pneumoniae

Answer 41

Penicillin, cephalosporins