Topic 1-11 Lecture 11

Question 1

What is the full name of S. pneumoniae?

Answer 1

Steptococcus pneumoniae

Question 2

What is the general characteristics of S. pneumoniae?

Answer 2

Non-motile (don't move)
non-sporulating (Don't make spores)
Gram-positive
Cocci shape (round)
Found as individual coccus, in pairs (diplococci), or in short chains

Question 3

Where does S.pneumoniae colonize?

Answer 3

Colonizes naspoharynx (usually no effects in 40% of ppl)
Transient member of microbiota

Question 4

What is S. pneumoniae sensitive to?

Answer 4

Temperature (heat and cold)

Drying

Question 5

How is S. pneumoniae transmitted?

Answer 5

Requires close person-to-person contact

Transmission via respiratory droplets

Question 6

What are the major virulence factors of S. penumoniae

Answer 6

Anti-phagocytic polysaccharide capsule
Adhesins
Pneumolysin (toxin that disrupts host cell membranes by opening pores within them)
Lipoteichoic acid (LTA) (Protein found in gram-positive bacteria)

Question 7

What are the clinical symptoms associated with S. penumoniae?

Answer 7

Pneumonia (inflammation of the lungs)
Bacteriemia (bacteria in the blood)
Meningitis (inflammation of the membranes surrounding the brain & spinal column)
Otitis media (Infection of the ear)

Question 8

What type of pathogen is S. pneumoniae?

Answer 8

It is an opportunistic pathogen

Question 9

What groups are at risk for S. pneumoniae infection?

Answer 9

People who are sick with influenza, measles (impaired immune system due to disease) (often follows upper respiratory tract infection)
Infants and young children
elderly patients
Smokers - Smoke injure airways and cilia, decreasing ability to clear microorganisms from the lungs
Alcoholics - alcohol is a sedative, diminish coughing and sneezing reflexes and interferes with macrophage activity)

Question 10

What is the name of the disease caused by S. pneumoniae?

Answer 10

Pneumococcal pneumonia

Question 11

What are the 2 forms of pneumococcal pneumonia?

Answer 11

Bronchial pneumonia (prevalent in the young and old, involves alveoli near to larger bronchioles)

Lobar pneumonia (prvalent in younger adults, involve single lobe of the lung (and possible more))

Question 12

How do the virulence factors of S. pneumoniae cause problems?

Answer 12

Capsule presents phagocytosis by macrophages

Lysis by bacteria will release pneumotoxins which damages mucosal cells. This impairs the ability to clear the bacteria and facilitates colonization in the lungs.

Toxins also impair gas exchange in the lungs and cause cyanosis (blue skin from lack of O2)

Question 13

What problems can happen if S. pnuemoniae entered the blood stream?

Answer 13

Release of pneumotoxin damages many cells, causing massive cytokine release resulting in fever and septic shock

Question 14

How do S. pneumoniae cause Meningitis?

Answer 14

Bacteria in bloodstream attach to meninges

Question 15

How is S. pneumoniae diagnosed?

Answer 15

Samples from sputum, blood, cerebrospinal fluid are tested using gram-positive staining, hemolytic activity, and bile sensitivity

Question 16

What are the types of hemolysis that S. pneumoniae can cause?

Answer 16

Alpha hemolysis (partial hemolysis) and Beta hemolysis (complete lysis of RBC)

Question 17

What are problems in diagnosing S. pneumoniae?

Answer 17

Difficult to grow bacteria

Sputum samples may be contaminated with bacteria from the mouth

Question 18

What are characteristics of the S. pneumoniae capsule?

Answer 18

90 types of identified capsules
Non-toxic
Does NOT induce inflammatory response
Ab-mediated response is possible

Question 19

How are different capsular types identified?

Answer 19

Serological testing - take a sample, mix with a monoclonal antibody, and look for “swelling” of the capsule (quellung reaction; quellung=swelling in German)

Question 20

How does the capsule of S. pneumoniae evade the host defences using capusles?

Answer 20

Encapsulated = pathogenic, no capusles = not pathogenic

Capsules can hide bacterial PAMPs such as PG; prevents formation of C3b complexation and opsonization

Question 21

What antibiotics are/were used to treat S. pneumoniae?

Answer 21

Penicillin and its derivatives (used to work, but resistance is becoming common)
Erythromycin or tetracycline - alternate treatment, but resistance also on the rise

Question 22

How are vaccines made for S. pneumoniae?

Answer 22

Vaccines made with purified capsular polysaccharide antigens (cross-reactivity is possible)
Conjugate vaccines (protein and polysaccharide antigens) have also been introduced to increase immune response

Question 23

What is cross-reactivity?

Answer 23

When an antibody against one serotype will bind to another serotype due to a shared epitope.

Question 24

Why do polysaccharide-based vaccines elict weak antibody responses?

Answer 24

Because polysaccharides are less immunogenic that proteins