streptococcus and enterococci Flashcards
streptococcus pneumoniae: histology & character
gram positive diplococci alpha haemolytic optochin susceptible; has capsule
normal flora carried in the thorat
streptococcus pneumoniae: culture
draughtsman colonies cultured on blood agar; raised rims with depressed centers
streptococcus pneumoniae: transmission
respiratory droplets
streptococcus pneumoniae: virulence factors
pneumolysins- membrane damaging toxins
anti-phagocytic capsule (different strains produce different types)
streptococcus pneumoniae: clinical presentations
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
streptococcus pneumoniae: diagnosis
pneumonia: sputum, blood cultures, antigen detection in urine
meningitis: csf, blood cultures, antigen detection in urine
streptococcus pneumoniae: treatment
benzylpenicillin/amoxicillin
ceftriaxone and vancomycin can be used for meningitis
streptococcus pneumoniae: prevention
polysaccharide vaccine: contains polysaccharide capsule
conjugation vaccine: contains capsule material + protein carrier (less valent hence better)
viridans streptococcus: character
gram positive cocci, alpha or non haemolytic, optochin resistant
normal flora of the mouth
viridans streptococcus: transmission
dental surgeries, chewing
viridans streptococcus: clinical presentations
dental caries
mucosa related infections
subacute endocarditis
streptococcus pyogenes: histology & character
group a beta haemolytic gram positive cocci in chains; catalase negative
*note: as opposed to staphylococci that are catalase positive
streptococcus pyogenes: transmission
respiratory droplets, direct contact
streptococcus pyogenes: virulence factors
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
streptococcus pyogenes: epidemiology
most common bacterial cause of pharyngitis, though the most common cause of pharyngitis is viral
streptococcus pyogenes: clinical presentations
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)
name the exotoxin mediated clinical presentations of s.pyogenes
1) scarlet fever 2) streptococcal toxic shock syndrome 3) necrotising fasciitis
describe the pathology of acute rheumatic fever
molecular mimicry - cross reacting b and t cells to the strep. antigens bind to the host components (immune complex deposition)
streptococcus pyogenes: diagnosis
serology: anti-streptolysin, or antibodies against DNAse b, or hyaluronidase
streptococcus pyogenes: treatment
penicillin
- clindamycin inhibits protein and hence toxin synthesis
- iv immunoglobulins clear the toxins)
streptococcus agalactiae: character
group b beta haemolytic streptococci
normal flora of vagina and colon
streptococcus agalactiae: virulence factors
different capsular polysaccharide types
streptococcus agalactiae: clinical presentations
neonatal sepsis:
early onset - pneumonia
late onset - meningitis
post partum infections in mother
streptococcus agalactiae: prevention
prophylactic penicillin
streptococcus agalactiae: treatment
penicillin + gentamycin
streptococcus dysgalactiae: character
group c or g beta haemolytic streptococci
found in non pasteurised milk
streptococcus dysgalactiae: clinical presentations
sore throat
soft tissue infections
group c - acute glomerulonephritis
group g - scarlet fever
streptococcus dysgalactiae: treatment
penicillin, erythromycin
enterococcus: character
not actually beta haemolytic
normal bowel flora
enterococcus: clinical presentations
urinary tract infection
intraabdominal infections
endocarditis
enterococcus: treatment
ampicillin/vancomycin
amoxicillin (used in UTI)
steptococcus bovis: clinical presentations
colon cancer
endocarditis
steptococcus bovis: treatment
penicillin
s. anginosus: character
normal flora of the gut and mouth
s. anginosus: clinical presentation
deep abscesses
s.anginosus: treatment
penicillin
abiotrophia spp.: character
normal flora of the mouth
nutritionally variant species
abiotrophia spp.: clinical presentation
endocarditis
