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
What’s a key difference between S. aureus and S. viridans when it comes to heart valves?
S. aureus eats heart valves quickly whereas S. viridans eat them slow.
Two subgroups of group D streptococci?
Enterococci and non-enterococci
Group D streptococci have what hemolytic characteristics?
alpha or gamma hemolytic
Enterococci are commonly the infectious agents in these four diseases?
1 urinary tract infections
2 biliary tract infections
3 bacteremia
4 subacute bacterial endocarditis
S. Bovis is associated with a type of cancer. Which is it?
Colon cancer
What is the most common cause of pneumonia in adults?
Streptococcus Pneumoniae
What is the most common cause of otitis media in children?
Streptococcus Pneumoniae
Otitis media are caused by three main bacteria, they are…?
1 Streptococcus Pneumoniae
2 Haemophilus influenzae
3 Moraxella catarrhalis
