streptococcus and enterococci

Question 1

streptococcus pneumoniae: histology & character

Answer 1

gram positive diplococci alpha haemolytic optochin susceptible; has capsule

normal flora carried in the thorat

Question 2

streptococcus pneumoniae: culture

Answer 2

draughtsman colonies cultured on blood agar; raised rims with depressed centers

Question 3

streptococcus pneumoniae: transmission

Answer 3

respiratory droplets

Question 4

streptococcus pneumoniae: virulence factors

Answer 4

pneumolysins- membrane damaging toxins

anti-phagocytic capsule (different strains produce different types)

Question 5

streptococcus pneumoniae: clinical presentations

Answer 5

pneumonia - commonly lobar, bronchopneumonia is possible too
meningitis - more severe than haemophilus influenzae and neisseria meningitis
septicaemia
upper respiratory tract infections- sinusitis, otitis media
spontaneous bacterial peritonitis
endocarditis

Question 6

streptococcus pneumoniae: diagnosis

Answer 6

pneumonia: sputum, blood cultures, antigen detection in urine
meningitis: csf, blood cultures, antigen detection in urine

Question 7

streptococcus pneumoniae: treatment

Answer 7

benzylpenicillin/amoxicillin

ceftriaxone and vancomycin can be used for meningitis

Question 8

streptococcus pneumoniae: prevention

Answer 8

polysaccharide vaccine: contains polysaccharide capsule

conjugation vaccine: contains capsule material + protein carrier (less valent hence better)

Question 9

viridans streptococcus: character

Answer 9

gram positive cocci, alpha or non haemolytic, optochin resistant

normal flora of the mouth

Question 10

viridans streptococcus: transmission

Answer 10

dental surgeries, chewing

Question 11

viridans streptococcus: clinical presentations

Answer 11

dental caries
mucosa related infections
subacute endocarditis

Question 12

streptococcus pyogenes: histology & character

Answer 12

group a beta haemolytic gram positive cocci in chains; catalase negative

*note: as opposed to staphylococci that are catalase positive

Question 13

streptococcus pyogenes: transmission

Answer 13

respiratory droplets, direct contact

Question 14

streptococcus pyogenes: virulence factors

Answer 14

streptolysins O & S: give s.pyogenes the beta haemolytic function, damages leukocytes
streptococcal pyogenic exotoxins: types abc causes fever, types ac causes scarlet fever, type a causes streptococcal toxin shock syndrome
enzymes: DNAse B, hyaluronidase
M proteins: prevents phagocytosis and killing

Question 15

streptococcus pyogenes: epidemiology

Answer 15

most common bacterial cause of pharyngitis, though the most common cause of pharyngitis is viral

Question 16

streptococcus pyogenes: clinical presentations

Answer 16

pharyngitis/tonsilitis (local complications include sinisitis, otitis media, post viral pneumonia)

skin & soft tissue infections: erysipelas (distinct border), impetigo, cellulitis

exotoxin mediated: scarlet fever, streptococcal toxic shock syndrome, necrotising fasciitis

post infection sequelae (non suppurative complications, NOT due to haematological spread; due to autoimmune response that attacks body tissues)
acute glomerulonephritis
acute rheumatic fever - polyarthritis & carditis
pathology: molecular mimicry- cross reacting b and t cells that are reacting to strep. antigens bind to the host components (immune complex deposition)

Question 17

name the exotoxin mediated clinical presentations of s.pyogenes

Answer 17

1) scarlet fever 2) streptococcal toxic shock syndrome 3) necrotising fasciitis

Question 18

describe the pathology of acute rheumatic fever

Answer 18

molecular mimicry - cross reacting b and t cells to the strep. antigens bind to the host components (immune complex deposition)

Question 19

streptococcus pyogenes: diagnosis

Answer 19

serology: anti-streptolysin, or antibodies against DNAse b, or hyaluronidase

Question 20

streptococcus pyogenes: treatment

Answer 20

penicillin

• clindamycin inhibits protein and hence toxin synthesis
• iv immunoglobulins clear the toxins)

Question 21

streptococcus agalactiae: character

Answer 21

group b beta haemolytic streptococci

normal flora of vagina and colon

Question 22

streptococcus agalactiae: virulence factors

Answer 22

different capsular polysaccharide types

Question 23

streptococcus agalactiae: clinical presentations

Answer 23

neonatal sepsis:
early onset - pneumonia
late onset - meningitis

post partum infections in mother

Question 24

streptococcus agalactiae: prevention

Answer 24

prophylactic penicillin

Question 25

streptococcus agalactiae: treatment

Answer 25

penicillin + gentamycin

Question 26

streptococcus dysgalactiae: character

Answer 26

group c or g beta haemolytic streptococci

found in non pasteurised milk

Question 27

streptococcus dysgalactiae: clinical presentations

Answer 27

sore throat
soft tissue infections
group c - acute glomerulonephritis
group g - scarlet fever

Question 28

streptococcus dysgalactiae: treatment

Answer 28

penicillin, erythromycin

Question 29

enterococcus: character

Answer 29

not actually beta haemolytic

normal bowel flora

Question 30

enterococcus: clinical presentations

Answer 30

urinary tract infection
intraabdominal infections
endocarditis

Question 31

enterococcus: treatment

Answer 31

ampicillin/vancomycin

amoxicillin (used in UTI)

Question 32

steptococcus bovis: clinical presentations

Answer 32

colon cancer

endocarditis

Question 33

steptococcus bovis: treatment

Answer 33

penicillin

Question 34

s. anginosus: character

Answer 34

normal flora of the gut and mouth

Question 35

s. anginosus: clinical presentation

Answer 35

deep abscesses

Question 36

s.anginosus: treatment

Answer 36

penicillin

Question 37

abiotrophia spp.: character

Answer 37

normal flora of the mouth

nutritionally variant species

Question 38

abiotrophia spp.: clinical presentation

Answer 38

endocarditis