Strep Throat

Streptococcus pyogenes

beta hemolytic bacitracin sensitive pharyngitis, necrotizing fascitis rheumatic fever (heart myosin cross reaction) scarlet fever (strawberry tongue and rash) glomerulonephritis

superantigens

cause the release of a large mount of cytokines IL-1 TNF and IL-2

Streptococcus

cocci in chains (straps) gram + catalase - (all streps are catalase -) Strep are differentiated three ways: lancefield groupings, hemolytic patterns biochemical properties

S pyogenes virulence factors cont.

hyaluronidase streptolysin S and O ( cause cell lysis (O), and can disrupt lysosomal membrane (S) after engulfment causing release of lysosomal contentsn (anti streplysin o and a antibodies are indicative of recent strep infection streptokinase A and B: activate a host blood factor -plasminogen by cleavage- this dissolves blood clots DNase: reduces viscosity of abscess material - helps them move through

Hemolytic activity

Beta hemolysis - complete hemolysis Both group A and group B strep A: pyogenes (bacitracin sensitive) B: agalactiae (bacitracin resistant)

Scarlet Fever

Complication of strep occurs when the strain is lysogenized by a tmperate bacteriophage - mediates production of a pyrogenic exotoxin Strawberry tongue and diffuse erythmatous rash focused to the trunk and folds of the body skin can desquamate

Diagnosing strep

History and Clinical presentation centor score exudate OR swelling on tonsils +1 tender OR swollen ANTERIOR cervical lymph nodes +1 Fever (>38) +1 Absence of cough +1 3-14 +1 15-44 0 45+ -1 1= further testing 2= cultures required 3 4 treat empirically

Streptococcus agalactiae

Mainly beta hemolytic ( some non ) bacitracin resistant Early onset of neonatal disease: septicemia, pneumonia and meningitis mothers are tested for group B strep before and after birth

S. pneumoniae

No grouping alpha hemolysis

Classic Streptococcal pharyngitis

Red swollen tonsils and pharynx Exudate on the tonsils High temperature swollen anterior cervical LN Usually lasts five days Transmitted by direct contact with nasal discharge Most of the time it will be viral-you must avoid using antibiotics when not necessary

Complications of strep

Scarlet fever Rheumatic fever (heart damage) M protein cross reacts with heart myosin leading to autoimmunity Post-streptococcal glomerulonephritis (M protein causes the deposition of antibody-antigen complexes that cause inflammation)

Lancefield groupings

Streptex - latex bead antibody-antigen compelxes define the strain

Top 4 \bacterial causes of strep thraot

Streptococcus pyogenes Corynebacterium diphtheriae (croup) Neisseria gonnorrhoeae Mycolpasma pneumoniae

S. pyogenes

acquired by inhaling a droplet that adheres to the epithelium Pathogenicity islands (groups of virulence genes expressed together) Strep M protein - confers antiphagocytic properties and exists on a large pathogenic island Fimbriae (short in length) along with M protein adheres to host cells (main antigenic component) f protein binds to fibronectin

Reasons to treat strep

avoid transmission avoid sequelae antibiotic overuse differentiate from ebV and other viruses

Group C and G

beta hemolysis Bacitracin resistant acute pharyngitis

GAS

pharyngitis impetigo (vesicles progressing to pustules) necrotizing fascitis rheumatic fever glomerulonephritis (hematuria and proteinuria inflammation of renal glomeruli streptococcal toxic shock syndrome

streptococcus methods of survivial (from the host)

produces C5a peptidase - prevents recruitment of phagocytic cells to site of infection M protein binds factor H leading to degradatioon of C3b - and strep has a hyaluronic capsule - these both prevent recognition by the innate immune system Avoid ingestion: have a hyaluronic capsule kill phagocytes by streptolysin If phagocytosed : produce streptolysin S which degrades lysosome able to avoid the adaptive: 50 different M protein types of M protein

Virulence factors

promote colonization adhesion and invasion