Microbiology - chapter 4 - Streptococci Flashcards
Streptococci are divided into three groups based on their hemolytic abilities. What are these three groups and their characteristics?
Alpha-hemolytic streptococci: partially lyse RBCs.
Beta-hemolytic streptococci: completely lyse RBCs.
Gamma-hemolytic streptococci: do not lyse RBCs(non-hemolytic).
Visual appearance of streptococci on light microscopy?
They line up after each other on a strip.
What is Lancefield antigen?
the characteristic C carbohydrate found in the cell wall. The C carbohydrate differ from each species of streptococci.
Which three Lancefield group streptococci are the most important clinically?
Lancefield group A, B and D
Which 5 spiecies of streptococci are significant human pathogens?
1 Lancefield group A 2 Lancefield group B 3 Lancefield group D 4 Streptococcus Pneumoniae 5 Viridans group streptococci
What can you read from the name “group A beta-hemolytic streptococci? What is another name for this group, and list four diseases that they can cause?
Lacfield group A that completely lyse RBCs.
Also called Streptococcus pyogens
group A beta-hemolytic streptococci cause the diseases - strep throat, scarlet fever, rheumatic fever and post-streptococcal glomerulonephritis.
Name the antigenic components of the streptococcal wall?
1 C carbohydrate
2 M protein - inhibits complement activation and protects the organism from phagocytosis
Name 7 enzymes that contribute to the pathogenicity of group A beta-hemolytic streptococci.
1 Streptolysin O - lyse RBC & WBC 2 Streptolysin S - lyse RBC & WBC 3 Pyrogenic exotoxin(erythrogenic exotoxin) - cause scarlet fever 4 Streptokinase - activate plasmin 5 hyaluronidase - break down ECM 6 DNAases 7 Anti-C5a peptidase
Group A beta-hemolytic Streptococci cause 4 types of disease by local invasion and/or exotoxin release, which?
1 Streptococcal pharyngitis
2 Streptococcal skin infections
3 Scarlet fever
4 Streptococcal toxic shock syndrome
Group A beta-hemolytic Streptococci cause 2 delayed antibody mediated diseases. Which?
1 Rheumatic fever
2 Glomerulonephritis
Erisypelas?
Streptococcal infection of superficial skin
About 25% of woman carry these bugs vaginally, and they are a cause of neonatal meningitis, pneumonia and sepsis?
Group B beta-hemolytic streptococci
Three bacteria are responsible for most meningitis aquired by babies coming out the birthcanal. Name them.
1 Listeria Monocytogenes
2 Escheria Coli
3 Group B streptococcus
Viridans group streptococci:
What type of hemolytic streptococci?
alpha-hemolytic strptococci
what three main types of infection are caused by viridans group streptococci?
1 dental infection
2 endocarditis
3 abscesses
