Gram Positive Cocci, Catalase Negative Flashcards
The group is antigen is unique, placing the organism in Lancefield group A.
Streptococcus pyogenes
is attached to the peptidoglycan of the cell wall and extends to the cell
surface
is essential for virulence S. pyogenes colonizes the throat and skin
on humans making these sites primary sources of transmission
Strepococcus pyogenes- M Protein
M protein encoded by the
genes emm
molecule causes streptococcal cell to resist phagocytosis and
plays a role in adherence of the bacterial cell to mucosal cells.
Steptococcus pyogenes-M protein
is the most common serotype seen in pharyngitis
M1 serotype
are adhesion
molecules that mediate attachment to host epithelial cells.
Fibronectin-binding protein (Protein F) and Lipotechoic acid-
- it prevents opsonized phagocytosis by neutrophils or
macrophages. It also allows the bacterium to mask its antigens and remain
unrecognized by its host
Hyaluronic acid capsule
Responsible for hemolysis on Sheep Blood Agar plates incubated
anaerobically, oxygen labile
Streptolysin O
yses leukocytes and is non-immunogenic
Oxygen stable
Streptolysin S
- spreading factor is an enzyme that solubilizes the ground
substance of mammalian connective tissues.
Hyaluronidase
red spreading rash
Streptococcal pyrogenic endotoxins/erythrogenic toxins
It is the most common clinical manifestation of Group A Streptococcus
Bacterial pharyngitis
include impetigo, cellulitis, erysipelas, wound
infection, or arthritis
Skin or pyodermal infections
- a localized skin disease, begins as small vesicles that progress
to weeping lesions
Impetigo
- rare infection of the skin and subcutaneous tissues observed
frequently in elderly patients
Erysipelas-
can develop following deeper invasion by streptococci.
cellulitis
An invasive infection characterized by rapidly progressing inflammation
and necrosis of the skin, subcutaneous fat, and fascia.
Necrotizing Fasciitis