Streptococcus pyogenes Flashcards
transmitted via
respiratory droplets or direct skin contact
frequently infects
skin or nasopharynx
reservoir
humans
causes ___% of streptococcal disease
90
causes diseases that are both ___ and ____
pyogenic, toxigenic
gram + or -
+
catalase + or -
-
coagulase + or -
-
penicillin resistant or sensitive
sensitive
factors that inhibit host immunity
hyaluronic acid capsule
M protein
adhesive/invasive factors
M protein
hyaluronidase
exotoxins
cytolytic exotoxins : streptomycin O and S
pyrogenic exotoxins: SpeA and SpeB
hyaluronic acid capsule
mimics the hyaluronic acid found in human connective tissue
hides the bacteria from phagocytes
M protein
important adhesion
prevents opsonization by breaking down complement C3b
Streptolycin O
lyses leukocytes and erythrocytes
SpeA
super antigen that causes helper T cells to release a cytokine storm leading to toxic shock
SpeB
protease that destroys tissue, leading to fluid accumulation in the areas of damage
genes for Spe toxins are encoded by a
temperate bacteriophage and therefore only lysogenized S. pyogenes strains can synthesis these toxins
lysogenic conversion
new host phenotype due to expressed genes from a phage
Streptococcal pharyngitis
S. pyogenes is inhaled and bacteria replicate in mucosa of the pharynx
- patches of pus on tonsils, in back of throat
- tonsil may be swollen , red and tender
- fever
- absence of cough and nasal discharge
- most common in 5-10 year old children
impetigo
enters through skin that is already irritated or raw
small, flattened, red patches that develop into pustules that eventually rupture and crust over with a honey colored crust
- highly contagious
cellulitis
spreads to the deeper dermis and subcutaneous tissues
- red puffy patches with ill-defined edges
- fever, cells, leukocytosis
- occurs in middle aged and elderly
necrotizing fasciitis
caused by highly virulent strains that produce SpeA and SpeB as well as other enzymes such as streptomycin O
- infects a wound
- the enzymes and toxins allow the bacteria to invade and destroy muscle, fat and organ fascia
- pain level inconsistent with the severity of the original injury
streptococcal toxic-shock syndrome
caused by streptococcal pyrogenic exotoxin (SpeA and B) and additional virulence factors
less common but more deadly than staphylococcal TSS
symptoms of streptococcal toxic-shock syndrome
high fever
diffuse sunburn-like rash
hypotension
shock
multi organ failure
BUT MAY INCLUDE NECROTIZING FASCIITIS
