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