MIDTERM 2 - Streptococcus Flashcards
= gram (+) cocci
= arranged in pairs or in chains
= catalase negative
Genus Streptococcus
very small zone of NO HEMOLYSIS and then a wider zone of β-hemolysis; mistaken as β hemolysis at first glance
Hemolytic pattern on sheep’s blood agar
= fastidious; grown in enriched media
= most are facultative anaerobes
= non-motile but would just grow along the stab line or
along the line of inoculation
Genus Streptococcus
classic strep throat; red swollen tonsils and pharynx; a purulent exudate on tonsils, fever,
swollen lymph nodes that usually lasts 5 days
Streptococcal pharyngitis
also known as Wide Zone
Alpha-Prime (α’)
type of infection, site of origin
Physiologic characteristics
enzyme destroys RBC & WBC and is the reason for beta-hemolytic ability
Streptolysin O
Lancefield antigens are given letter names_____________
through S.
A, B, C, D, E,
In Streptolysin S, S stands for _____
oxygen stabile
C carbohydrate present or extracted from the cell wall
Lancefield classification
antigen causing increased ASO titer
Streptolysin O
also responsible for beta-hemolysis but is not antigenic
Streptolysin S
more than 30 species of streptococci, only 5 are
significant human pathogens; Three of these pathogens have Lancefield antigens: Lancefeld group ___________
Lancefeld group A, B and D
major virulence factor for group A streptococcus. It inhibits the activation of complement and protects from phagocytosis; However, it is also the weakest point in the organism’s defense
M protein
pus-producing; strep throat, scarlet fever, rheumatic fever, & post-streptococcal
glomerulonephritis
Group A Beta-hemolytic Strep
cause scarlet fever; causes streptococcal toxic shock syndrome
Pyrogenic exotoxin | erythrogenic toxin
In Streptolysin O, O stands for _______ as it is inactivated by oxygen
oxygen labile
flesh eating strep; break in skin caused by trauma then follow a
path along fascia; patient develops swelling, heat, & redness that moves rapidly from initial infection site; day later skin changes from red to purple to blue, & large blisters form; later skin dies & muscle become infected
Necrotizing Fasciitis
produced pyrogenic toxin or erythrogenic toxin; fever, sorethroat & scarlet-red rash; rash begins on trunk and neck then spreads to extremities, sparing the face; strawberry tongue
Scarlet fever
Streptolysin S, S stands for _____
oxygen stabile
also responsible for beta-hemolysis but is not antigenic
Streptolysin S
infection of the dermis; raised, bright red rash with sharp
border
Erysipelas
similar to scarlet fever, also mediated by the release of pyrogenic toxin; signs and symptoms are similar with staph TSS
Streptococcal toxic shock syndrome
affects children 5-15 years of age; follows untreated streptococcal pharyngitis
NOT after a skin infection
Rheumatic fever
antibody-mediated inflammatory disease of glomeruli; occurs 1 week after infection of either pharynx OR skin by nephritogenic strains of S. pyogenes.
Acute post-streptococcal glomerulonephritis
normal flora of lower GIT; beta-hemolytic; 25% of women carry it vaginally which a baby can acquire during delivery causes neonatal (< 3 months of age) meningitis, pneumonia, sepsis
Group B Strep
occur first 3 days after birth (usually within 24 hours); commonly associated with obstetric complications and premature birth; causes neonatal pneumonia
Early – onset Infection
occurs between 1 week and 3 months after birth; causes neonatal meningitis; uncommonly associated with obstetric complications; organism is rarely found in the mother’s vagina prior to birth
Late – onset Infection
important virulence factor; prevents phagocytosis; ineffective after opsonization
Capsule
the most significant component of the capsule
Sialic acid
Loss of Sialic acid = ______
loss of virulence
major cause of bacterial pneumonia & meningitis in
adults; otitis media in children
appear as lancet-shaped, gram-positive cocci arranged in pairs (diplococci)
major virulence factor is its capsule
Pneumococcus
most of viridans streptococci are _______
alpha-hemolytic
S. mutans bind to teeth & ferment sugar producing acid and dental caries
Dental infections
Dental manipulations spreads organisms into the bloodstream then implants the heart, results in subacute bacterial endocarditis (SBE)
Endocarditis
normal flora of intestines; alpha hemolytic; urinary tract infections, biliary tract infections; one of the most common cause of nosocomial
infections
Enterococcus (S. faecalis, S. faecium)
association between S. bovis infection and colon cancer; 50% of people with S. bovis bacteremia have a colonic malignancy
Group D Strep (S. bovis, S. equinus)
normal flora of G.I. tract, nasopharynx and
gingival crevices
Viridan Group Streptococci
