Nelson - Ch. 183 Group A Streptococcus Flashcards
The beta hemolytic strep can be divided into groups by this group-specific polysaccharide
Lancefield C carbohydrate
Group A strains can be distinguished from other groups by differences in sensitivity to
Bacitracin
GAS can be subdivided into more than 220 serotypes in the basis of
M protein
T/F M types commonly associated with pharyngitis rarely cause skin infections and M types associated with skin infections rarely cause pharyngitis
T
T/F A few skin strains are associated with GN but many more pharyngeal strains are considered nephritogenic
F, More skin strains are associated nephritogenic
T/F Humans are the natural reservoir for GAS
T
Thie incidence of pharyngeal infection with GAS is highest in what age group
5-15 yrs of age, especially in young school-age
Incubation period for strep pharyngitis
2-5 days
Food containing GAS occasionally cause explosive outbreaks of
Tonsillopharyngitis
Children with GAS URTI are usually no longer infectious ___ hrs after appropriate antibiotic therapy has been started
24
___ and ___ can harbor GAS and play a role in disseminating impetigo
Fingernails and perianal region
Risk factors for invasive GAS infection
1) DM 2) HIV 3) IV drug use 4) chronic pulmonary or cardiac disease
The portal of entry is unknown in almost ___% of cases of severe invasive GAS infection
50
Virulence of GAS depends primarily on
M protein
Strains rich in M protein are more virulent because
M protein resist phagocytosis in fresh human blood
Toxins responsible for the rash of scarlet fever
Streptococcal pyrogenic exotoxins A, B, and C / erythrogenic toxin
T/F Strep exotoxins stimulate the formation of specific antitoxin antibodies that provide immunity against the scarlatiniform rash but not against other strep infections
T
GAS can produce up to ___ different pyrogenic exotoxins, and repeat attacks of scarlet fever are possible
12
Strep toxin associated with streptococcal TSS
Exotoxin A, B, and C
MC infections caused by GAS involve what organ systems
1) Respiratory tract 2) Skin and soft tissues
Rash of scarlet fever appears within ___ after onset of symptoms, although it may appear with the first signs of illness
24-48
Rash of scarlet fever often begins where
Around the neck and spreads over the trunk and extremities
T/F Rash of scarlet fever blanches on pressure
T
After ___ days, the rash of scarlet fever begins to fade and is followed by desquamation
3-4
Progression of desquamation of the rash of scarlet fever
Face progressing downward, resembling a mild sunburn
