Streptococci Flashcards
what are some characteristics of streptococci bacteria
gram positive (peptidoglycan), facultative anaerobes, non-spore forming
what are the 3 ways to classify stretococcus
hemolysis patterns
lancefield group
species
what are the 3 types of hemolysis patterns
alpha - partial hemolysis and green discoloration
beta - complete hemolysis
gamma - no hemolysis
what is the most prevalent disease of Group A streptococcal diseases
acute pharyngitis (strep throat)
how would you prevent acute rheumatic fever (ARF)
by treating primary disease of strep throat w/ penicilan
-ARF only comes after strep throat does not spontaneously come
what is the only site of infection post acute rheumatic fever (ARF)
pharynx
what disease follows strep throat, is caused by a group a streptococcus, and causes smoky urine
Acute post-streptococcal glomerulonephritis (APSGN)
how are group A streptococcus infections transmitted, what age group is most susceptible
person to person, school aged children
Group A infections cant penetrate intact skin so the must bind to mucous membrane using ______ ?
adhesins
what do GAS adhesins bind to on epithelial surfaces
fibronectin
what are streptococcus 2 most important virulence factors
streptokinase, and hylauropeptidase
what is the role of streptokinase
it allows bacteria to degrade/lyse blood clots
what are group a streptococcus 3 mechanisms to avoid phagocytosis
- M protein
- hyaluronic acid capsule
- C5a peptidase
what is C5a peptidase and how does it work
an anti-phagocytosis mechanism of GAS, and it inactivates phagocyte chemotaxins
what is M protein and how does it work
an anti-phagocytosis mechanism of GAS, and it binds to host proteins preventing normal immune defense
what is the hyaluronic acid capsule and how does it work
an anti-phagocytosis mechanism of GAS, and it makes the strep “slippery” so phagocytes have tough time attaching to it
what activates macrophages, causes T cells to release cytokines, and is responsible for the red rash of scarlet fever
superantigens
Group A and Group B streps both have what hemolysis pattern
Beta
what are some characteristics of Group B streps
- inhabit GI and female genital tracts
- have a polysaccharide capsule
- aerobic
Group D streps exhibit what kind of hemolysis pattern
alpha or gamma
enterococci and neneneterococci are what group of streps
Group D streps or the normal fora of GI and genitourinary tracts
what is the “worlds toughest pathogenic bacteria” and why
enterococci, because its resistant to most antibiotics and penicilan only inhabits this bacteria NOT KILL it
what strep is the most common cause of subacute bacterial endocarditis
viridans streptococci
what strep type is known as the “mutans” group and is responsible for dental caries
Viridans streptococci
how do viridans streps cause dental plaque
form polymers on sucrose then ferment sugar to lactic acid (demineralizes enamel)
-remain active at low pH
