Streptococcus Pneumonia

Question 1

List the general characteristics of streptococci

Answer 1

Non motile
Non sporing
Catalase negative
Facultative anerobe
Gram positive cocci
They grow in pairs and chains
Some species are capsulated

Question 2

The streptococci are divided on which basis?

Answer 2

Classic appearance on horse blood agar

Question 3

The streptococci are divided into??

Answer 3

Alpha
Beta
Non hemolytic (gamma)

Question 4

What feature on blood agar is characteristic of alpha hemolytic streptococci?

Answer 4

Incomplete haemolysis, resulting in greenish tinge.

Question 5

Examples of alpha hemolytic streptococci are?

Answer 5

S. Pneumonia and S. Viridans

Question 6

The feature on blood agar that is characteristic of beta hemolytic streptococci is?

Answer 6

Complete haemolysis, having a clear zone on blood agar.

Question 7

Beta hemolytic streptococci are grouped on the basis of??

Answer 7

On the basis of their lancefield carbohydrate antigen (a, b, c, f, g)

Question 8

Non hemolytic streptococci include?

Answer 8

Viridans
Anaerobic
Nutritionally variant streptococci

Question 9

List the viridans streptococci

Answer 9

S. Mitis
S. Mutants
S. Salivarius
S. Anginosus
S. Sanguinus

Question 10

The clinical features of s. Pneumonia include??

Answer 10

Bacterial pneumonia
Otitis media
Bacteriemia
Meningitis

Question 11

The species under alpha hemolytic strep include?

Answer 11

S. Pneumonia
Viridans streptococci

Question 12

The A lancefield group is made up of which spp??

Answer 12

S. Pyogens

Question 13

The invasive clinical syndromes for s. Pyogens are??

Answer 13

Necrotizing fascitis
Bacteriemia
GAS TSS

Question 14

The spp under lancefield group B include??

Answer 14

S. Agalactiae

Question 15

The clinical syndromes for s. Agalactiae are?

Answer 15

Neonatal meningitis
Bacteriemia

Question 16

The spp under lancefield group c are?

Answer 16

S. Dysgalactia
S. Equi

Question 17

The spp under lancefield group D include??

Answer 17

S. Bovis and others.

Question 18

What is the site of infection of s. Pneumonia?

Answer 18

Nasopharynx. It affects 5-10% of adult and 20-40% healthy children.

Question 19

What is the mode of transmission?

Answer 19

Inhalation of contaminated droplet nuclei.

Question 20

Invasive pneumococci is commonest in <2 and >65.
T/F

Answer 20

True.

Question 21

What are the risk factors for pneumococcal infection??

Answer 21

Antibody deficiencies
Complement deficiencies
Neutropenia
Asplenia
Malnutrition
Alcoholism
Chronic diseases
Overcrowding

Question 22

Pathogenesis of s. Pneumonia

Answer 22

Capsular Polysaccharide.
Cell wall Polysaccharide.
PspA
PspC
Pneumolysin
Autolysin
PsaA
Neuraminidase

Question 23

What is the fxn of neuramidase in s. Pneumonia?

Answer 23

Mediates adherence.

Question 24

What is the fxn of PsaA in s. Pneumonia?

Answer 24

Adherence

Question 25

What is the fxn of PspC in s. Pneumonia?

Answer 25

Inhibits phagocytosis by binding to complement H.

Question 26

What is the fxn of Autolysin?

Answer 26

Causes release of bacterial components and activates complement system.

Question 27

What properties give s. Pneumonia the ability to resist antibiotics?

Answer 27

Penicillin resistance - mutations in the pbp2x (high level resistance) and Pbp2A (low level resistance). Macrolide resistance - ermB (methylase enzyme) and MefA (efflox genes) confer resistance to macrolide antibiotics.

Question 28

What are the clinical features of s. Pneumonia?

Answer 28

1. Lobar pneumonia. 2. Pyogenic meningitis-expect in neonates. 3. Non invasive diseases like otitis media and Sinusitis. 4. Invasive diseases like osteomyelitis, septic arthritis, peritonitis, endocarditis, pericarditis etc.

Question 29

Diagnosis of s. Pneumonia??

Answer 29

1. BC bottles may flag positive but no result on gram stain because of autolysis of pneumococci. Pneumococcal antigen test on blood maybe positive. 2. Grows on routine media and causes alpha haemolysis on blood agar. May see central autolysis of colonies (draughtsmen). 3. Gram positive lancelot Diplococci often with visible capsule. 4. Catalase negative, optochin sensitive, soluble in 10% bile salt. 5. Penicillin MIC should be used for invasive isoletes

Question 30

Treatment for s. Pneumonia??

Answer 30

Penicillin MIC <0.1% use penicillin or ampicilin Penicillin mic 0.1-1.0% use ceftriaxone or ceftoxamide for meningitis.. High doses of penicillin for other infections Penicillin MIC >1.0 use vancomycine with/ wo refampicin for meningitis, ceftriaxone or high doses of penicillin, carbapenem or floroquinolones.

Question 31

What are the vacancies for s. Pneumonia??

Answer 31

13 valent pneumococcal conjugate vaccine given in three doses at 2, 4 and 12mnths respectively. 23 valent unconjugated vaccine given to pts >65 and also risk pts. Children with special risk should have pcv 13 followed by ppv23 after their second birthday. For prophylaxis, po penicillin but not for pts with csf leaks.