strep-pyogenes

Streptococcus spp

Large diverse group of human residents

Groups based on surface antigens(surface proteins) and hemolysis(digest blood)

Group A- streptococcus pyogenes

Group B- streptococcus pneumoniae & streptococcus agalantiae

Viridans group- streptococcus mutans

Gram positive

Spherical cells (coccus) in chains (strep)

Susceptible to drying (need to be in wetter places)

Key virulence factors

M protein- acts as an anchor to host cell tissues and antigenic mimicry (immune cells are blind to it bc they mimic our protiens)

Capsules- sugar based secretion surround individuals cells and repels phagocytic cells

Streptococcus pyogenes

Group A beta-hemolytic

Most serious strep pathogen

Many illnesses in relation to S aureus (cellulitis and impentigo)

Virulence

Streptokinase- enzyme protein blood thinner

Hyaluronidase- breaks down connective tissue

Streptococcal pharyngitis

Strep throat

Most common form of strep

1/3 are carriers

Petechial rash in oral cavity, acute fever, pus on tonsils

Scarlet fever

Strep pyogenes finds its way into the blood

High fever and examthem rash

Focal infection (bc it’s in the blood it can latch on to other tissues)

Sequelae of s pyogenes

Autoimmune inflammation

Rheumatic fever- results from focal s pyogenes infection after sepsis, inflammation of myocardium (heart wall) and endocardium (inner heart lining)

Acute glomerulonephritis- inflammation of bowman’s capsule (surrounds kidneys), results in kidney failure

Streptococcus pneumoniae

Group b alpha hemolytic (incomplete digestion of blood agar)

Presents in pairs rather than chains

Resident in upper respiratory tract

Most common cause of bacterial pneumoniae, acute otitis media (ear infection)

Asthma, smoking, or other respiratory infections all increase chance of pneumonia

Neonatal peds common