2c. Streptococcus Flashcards
What type of Gram stain are Streptococcus?
G(+).
What general shape does Streptococcus have?
Chains or pairs of cocci.
Are Streptococcus Catalase positive?
No. They are all catalase negative.
How are Streptococcus serogrouped?
They are serogrouped using know antibodies to the cell wall carbohydrates; Lancefield’s group A-O.
Whrere in the human bodies is the reservoir for Group A Streptococcus?
Human throat and skin.
Why are Streptococcus pneumoniae and viridans group not groupable?
Because they lack the carbohydrate cell wall antigens.
Which Streptococcus are beta hemolytic?
Streptococcus pyogenes, Streptococcus agalactiae.
Which Streptococcus are alpha hemolytic?
Streptococcus pneumoniae, and Streptococcus viridans group.
What is another name for Streptococcus faecalis?
Enterococcus faecalis. The enterococci belong to the Streptococcus family.
Which Streptococcus are PYR positive? What is the PYR test?
S. pyogenes and S. faecalis are both positive. The PYR test checks for the presence of pyrrolidonyl arylamidase.
Which Streptococcus is Bacitracin-sensitive?
Streptococcus pyogenes (A disk).
Which Streptococcus is Bacitracin-resistant?
Streptococcus agalactiae (P disk).
Which Streptococcus is cAMP test positive?
Streptococcus agalactiae.
Which Streptococcus is bile-soluble?
Streptococcus pneumoniae.
Which Streptococcus is Lancefield Group A?
Streptococcus pyogenes.
Which Streptococcus is Lancefield Group B?
Streptococcus agalactiae.
Which Streptococcus is Lancefield Group D?
Streptococcus faecalis and Streptococcus bovis (which is non-enterococci).
How is Group A Streptococcus spread?
By respiratory droplets or direct contact.
Which Streptococcus produces a hyaluronic acid capsule and what does it do?
Streptococcus pyogenes. It is a polysaccharide that is non-immunogenic; it inhibits phagocytic uptake.
What does the M protein do?
Virulence factor, antiphagocytic, used to TYPE group A strep.
What disease is M-12 protein associated with?
Acute glomerulonephritis.
Which streptolysin toxin is immunogenic? Which one isn’t?
Streptolysin O is immunogenic, Streptolysin S is not.
Streptokinase is a spreading factor that is part of the Streptococcus toxins. What does it do?
Breaks down fibrin clot.
What does Streptococcal DNase do?
Liquefies pus, extension of lesion.
What does hyaluronidase do and for what pathology is it important?
Hydrolyzes the ground substances of the connective tissues; important to spread in cellulitis.
What does the Exotoxins A-C do?
Secreted by S. pyogenes, causes fever and the rash of Scaler fever, inhibit liver clearance of endotoxin (from normal flora), creating shock-like conditions. It is also a superantigen, acitvating many helper T cells by bridgin T cell receptors and MHC class II markers without processed antigen.
What are three acute (suppurative) disease that S. pyogenes can cause?
Pharyngitis, Scarlet fever, Pyoderma/impetigo.
What is the treatment for Group A Streptococcus?
Becta-lactam or erythromycin.
How do we prevent reccurent S. pyogenes pharyngitis in rheumatic fever patients?
With Penicillin.
What species is part of the Group B Streptococci (GBS)?
Streptococcus agalactiae.
What does cAMP test-positive mean?
cAMP factor is a polypeptide that “compliments” a Staph aureus sphingomyelinase to make an area of new complete beta-hemolysis.
Where in the human body is the reservoir for S. agalactiae?
Colonizes human vagina in 15-20% of women.
What is the treatment for Group B Streptococcus?
Ampicillin with cefotazime or gentamicin.
What is a preventitive measure against GBS?
Treat mother prior to delivery if she has had a previous baby with GBS, has documented GBS colonization or prolonged rupture of membranes.
Which species of Streptococcus is inhibited by optochin?
S. pneumoniae.
Where in the human body is the reservoir for S. pneumoniae?
Human upper respiratory tract.
What toxin of S. pneumoniae damages respiratory epithelium, inhibits leukocyte respiratory burst and inhibits classical complement fixation?
Pneumolysin O.
What type of pneumonia does S. pneumoniae cause?
Typical pneumonia. Produces a lobar pneumonia with a productive cough, grows on blood agar, and usually responds well to penicillin treatment.
What is the treatment for pneumonia caused by S. pneumoniae?
Penicillin G.
What is the treatment for meningitis caused by S. pneumoniae?
Vancomycin +/- rifampin.
What are two species of Viridans Streptococci?
S. sanguis, S. mutans.
Where in the human body is the reservoir for Viridans Streptococci?
Human oropharynx (normal flora).
Which species of Streptococcus causes dental caries and how?
S. mutans dextran-mediated adherence glues oral flora onto teeth, forming plaque and causing caries.
What is the treatment for Viridans Streptocci?
Penicillin G with aminoglycosides for endocarditis.
What can E. faecalis do that other Streptococci can’t?
Hydrolyze esculin in 40% bile and 6.5 NaCl (bile esculin agar turns black).
