streptococcus Flashcards
do streptococcus persist in the environment?
no
what is classification of streptococci based on?
based on hemolysis
what king of bacteria are streptococcus?
pyogenic gram positive cocci
where are streptococcus part of the normal flora
- upper resp tract
- lower genitourinary tract
are streptococcus catalase pos or neg?
catalase negative
classification of streptococci based on serology:
-based on carb called Substance C on cell surface
what is streptococci’s pyogenic group?
species that cause pyogenic infections in humans and animals
-generally beta hemolytic
what is streptococci’s oral or viridans group?
primarily commensals on mucous membrane
-alpha hemolytic
what is streptococci’s lactic group?
present in milk and milk products
what is streptococci’s enteric group?
present in intestinal conents
what are streptococci’s virulence factors?
- adhesins : bind to a variety of extracellular matrix proteins of the host (fibrinogen, fibronectin, collagen etc)
- coating of these cells masks sites for complement activation and thus decrease opsonization
streptococci’s surface proteins
- M protein bind to fibrinogen and imparts an antiphagocytic property and enhances adherence to host epithelial cells
- FbsA protein
- FOG protein
streptococci’s capsule
S. pyogenesand S. equi produce capsule composed of hyaluronic acid
- poor antigenic activity and is antiphagocytic
- S. agalactae, S. porcinus, S. canis have capsules composed of poly saccharide and not hyaluronic acid
streptococci’s cell wall components
-peptidoglycan and lipoteichoic acid: interact with macrophages to release proinflammatory cytokines
streptococci’s hemolysins
- streptolysin O (SLO): oxygen labile
- pore-forming toxin
- suilysin is the SLO of S. suis
- streptolyin S: oxygen stable
- responsible for beta hemolysis
- cytolytic to macroohages, leukocytes, platelets, etc
what does streptokinase do?
activates plasminogen to form plasmin
- gene is located on prophage
- plasmin is a proteolytic enzyme that acts on host proteins, including fibrin (dissolve blood clots)
what are two other enzymes produces by streptococci
- hyaluronidase
- DNAse
what is streptococci’s pathogenesis
- primarily cause pyogenic infections that affect skin, resp tract, repro tract and mammary gland
- organisms may enter the blood to cause septicemia
- toxemia and immune-mediated lesions are common sequel of the disease
describe S. puogenes as a disease in humans
-beta hemolytic streptococci
-acute pharyngitis or strep
variety of skin infections (pyoderma)
-impetigo: benign infections of the superficial layers of skin result in crusty honey-colored lesions
-erysipelas and cellulitis: infections of the deeper layers of skin are called erysipelas and cellulitis
what does S pneumoniae cause in humans
pneumonia, meningitis, and sepsis
what species of streptococci cause bovine mastitis?
- S. agalactiae
- S. dysgalactiae
- S. uberis
what species of streptococci causes strangles?
S. equi subsp. equi
what streptococci causes infection in pigs?
S. suis
what bacteria causes chronic contagious mastisis?
S. agalactiae
what is the mode of infection of S. agalactiae
via the teat
what is the capsule of S. agalactiae
antiphagocytic activity
what are the surface proteins on S. agalactiae
ones involved in adhesion, invasion and inhibition of phagocytosis
what does CAMP factor do
potentiates the action of staphylococcal beta toxin
-has cytotoxic activaty against mammary tissue
what are two pathogenic things about S. agalactiae
- death of PMNs and release of lysosomal enzymes cause the tissue damage and inflammaion
- fibrin plug formation in the smaller molk ducts lead to involution of secretory tissue and loss of milk production
what is the treatment for S. agalactiae infections
- highlysusceptible to penicillins
- treated with ‘blitz treatment’-milk is cultures and positive cows are treated
what causes acute and subclinical mastitis in cows?
S. dysgalactiae
what is the significance of S. dysgalactiae subsp equisimilis
- beta hemolytic
- abscesses in horses; arthritis, meningitis, endometritis, mastitis
- joint infections of piglets
how does S. dysgalactiae infect and animal
- typically through and injury
- opportunity infection
- associated with other bacteria
what bacteria are most commonly found isolated from joint infections of piglets?
S. dysgalactiae sub sp equisimilis
where are S. uberis found?
commensal of cattle: tonsillar and intestinal, mucosal and epithelial cells
-20-30% of the cases of mastitis in US
how does S. uberis enter the cows?
- entry though the teat canal
- organisms attach and proliferate and induce influx of neutrophils
- edema and vacuolation of secretory cells
- necrosis of the alveoli
- severity varies
