Streptococcus pyogenes (group a) “the pie genies’ bakery”

STREPTOCOCCUS PYOGENES (GROUP A) “THE PIE GENIES’ BAKERY”  General features: gram+ cocci in chains, catalase-, beta-hemolytic (“beta-light bulb heating lamp over pie”), encapsulated with
hyaluronic acid capsule (“glass case over Hot Apple pie”), bacitracin sensitive (“basset hound able to eat the treats”),
pyrrolidonyl arylamidase (PYR)+
 Reservoir: human throat, skin
 Transmission: direct contact, respiratory droplets
 Pathogenesis: Hyaluronic acid is non-immunogenic and hydrolyzes the ground substances of connective tissues, M-protein of
cell wall carbohydrates is antiphagocytic (“master chef wearing an ‘M’ hat is swatting away the baker trying to eat his
cupcakes”), streptolysin O is immunogenic, hemolysin/ cytolysin (“O-shaped donuts on counter leaking as if lysed”), streptolysin
S is not immunogenic, hemolysin/ cytolysin
 Spreading Factors: streptokinase breaks down fibrin clot (“little muffins with P phosphates”), streptococcal DNAse liquefies pus,
extends lesions (“represented by twist breads”), streptococcal pyrogenic exotoxins A and C are phage-coded (i.e. cells are lysogenized by a phage) and cause fever and rash of
scarlet fever; B causes necrotizing fasciitis
 Diseases:
• Pyoderma/ Impetigo – symptoms of pyogenic skin infection with honey-crusted lesions = “baker holding lemon-crusted lemon-pie
• Pharyngitis/ Strep Throat – symptoms of abrupt onset of sore throat, fever, malaise, headache; tonsillar abscesses and tender anterior cervical lymph nodes = “bakers
wearing red handkerchiefs around necks”
• Cellulitis/ Erysipelas – erythema of skin = “baker wearing big red mittens”
• Scarlet Fever – symptoms of pharyngitis followed by a blanching “sandpaper” rash with palms and soles and face usually spared (“gingerbread man on counter with red
frosting covering most of body”), circumoral pallor, strawberry tongue (“backer with tongue out about to lick strawberry”), and nausea and vomiting.
• Toxic Shock-Like Syndrome and Necrotizing Fasciitis – superantigen invades fascia under the skin and spreads very rapidly; becomes a medical emergency and
amputations are common = “baker wearing super cape with lightning bolt with a burnt gingerbread man with leg amputated and “B” for exotoxin superantigen causing
• Rheumatic Fever – a sequelae of pharyngitis 2 weeks after infection; in a type II hypersensitivity, the M protein virulence factor mimics the myosin in our hearts causing
our own antibodies to attack the heart, specifically the mitral valve (“Master chef wearing miter hat”), other symptoms of RF categorized by JONES pneumonic
o J = joints/ polyarthritis (“backer pumping into J cupcake now with frosting on elbow”), O in shape of heart = heart problems of valve-defect, myocarditis, pericarditis
(“heart shaped O”), N = nodules, subcutaneous, that appear on extensor surface of forearm, elbows, and knees (“candies on cupcake”), E = erythema marginatum, a
rash with red borders (“frosting on cupcake to look like rash”), S = Sydenham’s chorea of rapid involuntary movements of the hands and face (“cupcake falling”)
• Acute Glomerulonephritis – a sequelae of pharyngitis and impetigo skin infection (“red handkerchief and honey-crusted crumbs on face of baker”), occurs 2 weeks after
infection (“calendar with circle two weeks after current date”); a type III hypersensitivity where immune complexes bind to the glomerulus (“baker talking on telephone
with cord twisted in shape of glomerulus”), causes edema (“baker has puffy cheeks”) and hypertension, as well as “smoky, cola-colored” urine (“cola-bottle by baker’s
 Laboratory Diagnosis: rapid strep test (ELISA-based) misses approx. 25% of infections; culture all negatives. Antibodies to streptolysin O (ASO) titer of >200 is significant for RF =
(“lady buying box of donut O’s checking them with antibody tongs
 Treatment: Penicillin, although it doesn’t protect from glomerulonephritis = “chef with PSGN holding the pencil”; macrolides used in penicillin allergy
 Prevention: Prophylactic antibiotics should be considered in patients for at least 5 years post-acute RF; beta lactams (penicillin) and macrolides