Streptococcus

Question 2

Streptococcus

Answer 2

Gram positive cocci, chains, facultative anaerobes, non-spore forming, fastidius, beta or alpha hemolysis, pyogenic/suppurative infections. Commensals on mucous membranes (URT, lower urogenital tract). DO NOT SURVIVE WELL OUTSIDE HOST.

Question 3

Strep diagnosis

Answer 3

Lancefield typing - based on differences in carb antigen in cell wall; uses antisera against the different antigens. Edwards media - for selective isolation of S. agalactiae and other strep involved in bovine mastitis. Biochemical tests.

Question 4

Strep Pathogenesis

Answer 4

S. equi - strangles. S. equi subsp zooepidemicus - wound infection, metritis, mastitis. S. uberis - bovine mastitis (also S. agalactiae, S. dysgalactiae). S. canis - lymphadenitits, infertility, fading puppies (septicemia). S. suis - meningitis (**zoonotic**).

Question 5

Strep Virulence Factors

Answer 5

ADHERENCE: Fibronectin Binding Proteins. ANTI-CHEMOTAXIS: C5a Peptidase. ANTI-OPSONIC/ANTI-PHAGOCYTIC: Capsule, M-protein, Hemolysins. DEGRADATIVE ENZYMES: DNAses, Proteases, Hylauronidase, Streptokinase. TOXINS: Superantigens (? important ?).

Question 6

M-Protein (Strep)

Answer 6

Anchored in cell membrane and cell wall, binds factor H (host serum protein) which prevents opsonisation. Binds host IgG, masking the bacteria. Binds fibrinogen, again masking itself.

Question 7

Strangles

Answer 7

Strep equi. Pharyngitis, lymphadenitis, fever. Most frequently dx contagious equine dz worldwide. Vaccine available: live genetically modified; initial vaccination is 2 vaccines 4 weeks apart; re-vaccine is q3 months (high risks horses) or q6 months (medium risk horses).