streptococcus Flashcards
process of identify strep
1) hemolysis
2) if beta-hemolysis, test for carbohydrate A-O with exception of D
3) if A, check M protein 1-90
strep group A known as:
S. pyogenes
appearance of gamma hemolysis
nothing
appearance of alpha hemolysis
- cloudy green due to remaining intact RBCs with altered green heme pigment
appearance of beta hemolysis
- clear, fully lysis of RBCs
S. pyogenes, where found?
skin, oropharynx
S. pyogenes extracellular proteins for bacterial proliferation
- streptolysins - lyse red cells, cause beta-hemolysis, O is oxygen labile, antigenic, leads to ASO antibody titers important in lab diagnosis, S is poorly antigenic and oxygen stable
- streptokinase - proteolysis, destroys fibrin clots
- DNAase
S. pyogenes antiphagocytic elements
- hyaluronic acid capsule
- M-proteins, strains with large amount of M-protein are more resistant to phagocytosis
what does Spe stand for?
streptococcal pyrogenic extoxin
what is caused by SpeA, B, and/or C?
- rash of scarlet fever
- strep toxic shock syndrome
what are the S. pyogenes toxin-mediated diseases?
- scarlet fever
- strep toxic shock syndrome
characteristics of strep toxic shock syndrome
- severe hypotension
- two or more of following: impaired renal function, DIC, impaired liver function, resp distress, rash, soft tissue necrosis
S. pyogenes invasive syndromes
- puerperal fever - uncommon in developed countries, infection of uterus immediately after childbirth
- acute pharyngitis/tonsilitis (strep throat)
- impetigo - mild child superficial skin infection
- erysipelas - severe cellulitis of dermis and underlying tissue
- necrotizing fasciitis - flesh-eating bacteria disease
what is a good test to narrow strep down to group A?
if it is sensitive to bacitracin, other groups are resistant
2 sequelae of S. pyogenes
- rheumatic fever - 2-3 weeks after sore throat, antibodies react with antigens on heart etc.
- acute glomerulonephritis - immune complexes deposit that contain bacterial antigens
test for recent S. pyogenes infection
- titer of 160 or greater for antibody to streptolysin O or four-fold increase in ASO titer
S. pyogenes treatment
PENICILLIN - no resistance to penicillin recorded
most important species of group B strep
S. agalactiae
S. agalactiae, where found?
vagina, colon
major disease from S. agalactiae
1/3 of neonatal infections - septicemia, meningitis, pneumonia, death
two epidemiological patterns of S. agalactiae
- early onset - vaginal during birth, penicillin or ampicillin
- late onset - infant to infant spread within nursery
group D strep are known as:
enterococci
entercocci, where found?
common inhabitants of GI tract
common diseases from enterococci
UTI, wound infections, sepsis
enterococci treatment
- resistant to many antibiotics
- vancomycin is last resort
most important enterococci species
- E. faecalis
- E. faecium
viridans streptococci hemolysis?
alpha hemolysis
most common viridans streptococci species:
- S. mutans
- S. sanguis
viridans streptococci, where found?
mouth, nose, pharynx
diseases caused by viridans streptococci
- frequent cause of INFECTIVE ENDOCARDITIS, often fatal when untreated
streptococcus pneumoniae known as:
pneumococcus
pneumococcus gram stain and shape
diplococci, lancet shaped, gram positive
pneumococcus pathogenesis
- pneumococcal capsule hinders phagocytosis
- IgA protease degrades surface IgA on respiratory epithelium
- pneumolysin, lytic enzyme contributes to pathogenesis
pneumococcus disease
- most frequent cause of bacterial pneumonia (cough, fever, chills, lung pain, rusty sputum, leukocytosis,
- meningitis
- otitis
who are at high risk for pneumococcal pneumonia?
- immunocompromised
- splenectomy
- sickle cell anemia
