Lecture 8 -- Streptococci Flashcards
what bacteria causes strep throat?
streptococci pyogenes
what disease(s) does streptococci agalactiae cause?
sepsis in newborns
what disease(s) does streptococci pneumoniae cause?
pneumonia and meningitis
name 3 streptococci species commonly associated with human disease
streptococci pyogenes
streptococci agalatiae
streptococci pneumoniae
are streptococci gram (+) or gram (-)
gram (+)
are streptococci catalase (+) or (-)
(-)
are streptococci aerobic or anaerobic
anaerobic
how do streptococci grow?
in pairs or chains
do streptococci have spores? do they have flagella?
neither
differentiate between the capsule of staphylococci and streptococci
capsule of staphylococci is made of polysaccharides
capsule of streptococci is made of hyaluronic acid that blends in with the hyaluronic acid of human connective tissue to evade the immune system
what is unique about the requirements for streptococci to grow
streptococci has complex nutritional requirements in order to grow
produce lactic acid by the fermentation of carbohydrates
name the 3 main GROUPS of streptococci and explain them
- streptococci (different variations of carbohydrate chains called LANCEFIELD CELL WALL ANTIGENS. different from strain to strain)
- pneumococcus – ONLY includes streptococci pneumoniae
- viridians – resident oral microbiota
state the important lancefield classifications relevant to human disease
group A strep – streptococci pyogenes
group B strep – streptococci agalctiae
streptococcal groups (streptococci, pneumococcus, viridians) are also classified based on ____ patterns
HEMOLYTIC (ability to lyse red blood cells)
explain the hemolytic pattern classification for streptococci
beta hemolytic – complete hemolysis (streptococci)
alpha hemolytic – incomplete hemolysis (pneumococcus and viridians)
gamma hemolytic = non hemolytic. dont produce porin toxins
which streptococci are beta hemolytic? what does this mean?
streptococci (classified by lancefield cell wall antigens.GAS and GBS)— they can completely lyse RBCs
which streptococci are alpha hemolytic? what does this mean?
incomplete hemolysis
pneumococcus and viridians
differentiate between the capsules of streptococcus pyogenes, streptococcus agalactiae, and streptococcus pneumoniae
pyogenes – hyaluronic acid
agalactiae – sialic acid
pneumoniae – polysaccharide
which streptococcus has M protein as a surface protein?
it is homologous to what other surface protein?
streptococcus pyogenes
it is homologous so Surface Protein A (SpA) of staphylococcus aureus – binds antibodies upside down
which group of streptococci has strepSAgs?
streptococcus pyogenes
what is the name of the porin protein for streptococcus pyogenes? what about streptococcus pneumoniae?
streptococcus pyogenes – streptolysin O
streptococcus pneumoniae – pnemolysin
which group of streptococcus can cause toxic shock syndrome with the production of superantigens?
strptococcus pyogenes
which group of streptococcus causes impetigo (school sores)
streptococcus pyogenes (group A strep GAS)
which bacteria avoids opsonization and phagocytosis due to its capsule?
GAS (streptococcus pyogenes) – due to hyaluronic capsule. poses as host
how does streptococcus pyogenes invade cells?
by binding to factor H – a complement control protein on the host cell surface
besides staphylococcus aureus, what other bacteria binds fibronectin and through what?
through F protein AND lipoteichoic acid – GAS (streptococcus pyogenes)
explain how streptococcus pyogenes can invade the host complement system
has an M protein that blocks C3b binding
has C5a peptidase to inactivate C5a
what does streptococcus pyogens have that enables it to evade opsonization/neutralization
M-like surface proteins that bind the Fc regions of antibodies (upside down)
hyaluronic acid
name the 5 toxins/enzymes that streptococcus pyogenes utilizes
superantigens
streptolysin S – a hemolysin
streptolysin O – a hemolysin
streptokinases – lyse clots
Dnases A-D – degrade host DNA
Streptococcus pyogenes is Beta hemolytic.
name the porin protein(s)
streptolysin S and Streptolysin O
GAS can cause ____ or ____ diseases
Suppurative or nonsuppurative (pus forming)
name the 5 pus forming diseases caused by GAS
-pharyngitis
-impetigo
-erysipelas
-cellulitis
-necrotizing fasciitis
name the non-supparative diseases caused by GAS
rheumatic fever
acute glomerulonephritis
what is also known as scarlet fever? what causes it?
pharyngitis
GAS
pharyngitis is ___ mediated
bacteriophage
what is rheumatic fever?
what causes it?
complications of pharyngitis that involve the heart, blood vessels and joints
occurs when GAS gets into the bloodstream
what is the only member of the GBS family
streptococcus agalactiae
streptococcus agalactiae is ___ hemolytic
beta, but there are a few gamma
of the 3 main species of streptococcus, which can colonize the GI tract? explain
streptococcus pyogenes and streptococcus agalactiae
this is because pyogenes has a hyaluronic acid capsule and agalactiae has sialic acid capsule. both are well protected to survive the conditions of the GI tract
explain the significance of the fact that streptococcus agalactiae can colonize the genitourinary tract
this bacteria primarily infects newborns – can catch right after being born or even in utero
there is both early onset and late onset
what is required to kill group B strep?
the activation of both the ALTERNATIVE and CLASSICAL complement pathways
true or false
group B strep has only 1 virulence factor
TRUE – its the sialic acid capsule. avoids phagocytosis
explain the entire capsule/ outer surface of group B strep
has sialic acid capsule to avoid phagocytosis.
also, has type-specific capsular carbohydrates (9 diff ones)
the sialic acid capsule can bind factor H and evade the complement system by breaking down C3b
also has PILLI that can bind to fibronectin on the host cell membrane
explain the difference between early onset and late onset neonatal disease of GBS
early onset == acquired in utero or at birth
disease = bacteremia, pneumonia or meningitis. sepsis. signs start showing up during first 7 days of life
late onset == starts showing up 1 week - 3 months after birth. EXOGENOUS SOURCE – we’re not sure where it came from
bacteremia with meningitis
name the symptoms that can be caused by a GBS infection
postpartum endometriosis
UTI
bacteremia
pneumonia
bone and joint infections
skin and soft tissue infections
is streptococcus pneumoniae encapsulated?
yes, with a polysaccharide capsule there are 90 different serotypes of the capsule
streptococcus pneumoniae are ____ hemolytic
alpha, but there are a few beta
which streptococci is diplococci?
streptococcus pneumoniae
which streptococcus PRODUCES lactic acid?
streptococcus pneumoniae
where does streptococcus pneumoniae colonize?
the nasopharynx and oropharynx
explain how streptococcus pneumoniae colonizes
initially colonizes through binding to PHOSPHO-CHOLINE on the host cell membrane.
streptococcus pneumoniae has choline binding proteins
explain the structure of streptococcus pneumoniae
elongated, diplococci
pnemococcus primarily enters through….
inhalation
pneumococcus can cause….
pneumonia and meningitis once it gets into the bloodstream
_____________ allows for the spread of streptococcus pneumoniae
the evasion of immune-cell mediated destruction
explain how pneumococcus effectively infects the lung area
pneumococcus bacteria is inhaled in.
it contains a secretory IgA protease. Thus, it degrades the IgA antibodies on the mucosal surfaces of the resporatory tract to easily infect and get into the bloodstream
also has PNEUMOLYSIN to form pores in epithelial cell walls and SUPPRESS the oxidative burst of phagocytes that is meant to kill them
also, activates the complement pathway to promote inflammation
name all of the virulence factors of pneumococcus
-secretory IgA protease
-Neuraminidase
-polysaccharide capsule
-pneumolysin
-surface choline binding protein
in order to develop pneumonia, what must happen?
ANTIBODY MEDIATED KILLING – destruction of IgA by IgA protease on pneumococcus
explain what pneumonia is
when pneumococcus colonizes in the alveoli of the lungs, pneumolysin destroys many epithelial cells, creating a lot of cell debris and fluid in the alveolar spaces
besides pneumonia, what else can streptococcus pneumonia cause?
sinusitis
otitis media (middle ear infection)
meningitis (following a ear or sinus infection)
bacteremia — heart valve tissue destruction
