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Cellular Microbiology and Virology > Streptococci > Flashcards

Streptococci Flashcards

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Biology 101 flashcards
1
Q

What is Streptococci

A
  • Streptococcus is genus of gram-positive coccus
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2
Q

How does Streptococci divide?

A
  • Spherical cells divide only in ONE PLAIN and form chains or pairs
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3
Q

Does streptococci require complex media for growth?

A
  • Yes
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4
Q

What shaped cells are they?

A
  • Spherical Cells (chained)
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5
Q

What haem group are they unable to make ?

A
  • Unable to make haem group of cytochromes or catalase
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6
Q

What are Streptococci grown on ?

A
  • Grown on blood agar (good source of catalase)
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7
Q

What are the different groupings of Streptococci?

A
  • Streptococci I: Hemolysis
  • Streptococci II: Antigenically / Serologically
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8
Q

What is the first grouping of Streptococcis?

A

-hemolysis

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9
Q

How does Hemolysis work?

A
  • Put on blood agar
  • Looking into the pattern of haemolysis
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10
Q

What are the different outcomes of haemolysis

A
  • Beta, Alpha and Gamma hemolysis
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11
Q

What is Beta haemolysis ?

A
  • Complete lysis of the red blood cell
  • Clear zone
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12
Q

What is Alpha haemolysis?

A
  • incomplete haemolysis of red blood cells
  • Produce a greenish-brown zone
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13
Q

What is Gamma haemolysis?

A
  • no haemolysis at all
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14
Q

What is the Lancefield Grouping for?

A
  • For Beta - hemolytic Streps
  • A, B, C, D …. W
  • Based on the specific carbohydrate antigen extracted by heating cells up to 150 degrees
  • About 20 groups
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15
Q

What are the Group A Streptococcus ?

A
  • Group A Strep = Streptococcus pyogenes
  • Beta hemolytic
  • Sensitive to bacitracin
  • Causes many of the streptococcal diseases of humans
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16
Q

Explain the importance of the Antigenicity of M-proteins of Group A Streptococcus

A
  • Antigenicity of M-proteins in the cell wall provides sub-classification of group A into over 100 sub-serotypes
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17
Q

What is the habitat of Group A Streptococcus and give the numbers

A
  • 5-30% of healthy people may be carriers of group A, beta hemolytic Streps in their throat and nasopharynx; however numbers are usually low
18
Q

What can group A streps cause? (suppurative)

A
  • Strep throat, impetigo skin infection, cellulitis and necrotising fasciitis
19
Q

What causes Scarlet fever?

A
  • Usually result of Strep sore throat caused by a pyrogenic toxin-producing organism
  • Toxin (A, B and C) encoded by a phage
20
Q

What are symptoms of Scarlet fever?

A
  • Fever, susceptibility to endotoxic shock, erythematous rash
21
Q

What non-suppurative diseases can Streptococcus pyogenes cause?

A
  • Rheumatic fever and Glomerulonephritis
22
Q

what causes Rheumatic fever

A
  • Occurs in a small percentage of individuals, 2-3 weeks after an untreated pharyngeal infection that was caused by a Beta-haemolytic group A strep
23
Q

What does Rheumatic fever affect? How

A
  • Joints and heart affected
  • Recovery occurs without residual injury to the joints but serious damage to heart valves causes rheumatic heart disease
24
Q

What causes Glomerulonephritis

A
  • Occur about a week after group A strep infection (skin or throat)
  • Also through an immunological reaction in which a strep directed antibody reacts with the glomerular basement membrane
25
Q

What does Glomerulonephritis lead to

A
  • Leads to loss of protein (blood initially in urine) through kidneys and hypertension
  • Can lead to chronic glomerulonephritis and kidney failure
26
Q

What is the predominant species of Group B Lancefield?

A
  • Streptococci agalactiae
27
Q

What is the % of women that has S. agalactiae present on their vagina?

A
  • 25%
28
Q

How does S. agalactiae affect new borns

A
  • May cause serious infections to new born
  • includes high fatality rates
29
Q

What is Group D Streptococci also known as

A
  • Enterococci
30
Q

What is a problem with group D Streps (Enterococci)

A
  • Major problem of vancomycin-resistance
31
Q

What is Streptococci viridans

A
  • Alpha hemolytic
  • Strep. Viridans is not a species but a large group of bacteria include many species that are normal inhabitants of throat and nasopharynx of humans
32
Q
  • What is Streptococci mutans
A
  • An example of Streptococci viridans species
  • causes dental caries
33
Q

How are Viridans Streptococci significant

A
  • cause of bacterial endocarditis - infection of heart valve - invariably fatal if not treated
34
Q

It can cause acute lung inflammation
Chills, fever and pleural pain. Alveoli fill with exudate
Bacteremia occurs in 25% and Pneumococci may invade other tissues.
What am I?

A
  • Streptococcus pneumoniae
35
Q

How is Streptococcus pneumoniae shaped

A
  • Lancet shaped organism.
  • Usually shaped in pairs (Diplococcus)
36
Q

How does Streptococcus pneumoniae resistant to phagocytosis

A
  • Virulent organisms are encapsulated
37
Q

How is Streptococcus pneumoniae subdivided

A
  • Subdivided into 90 types on the basis of antigenicity of capsular polysaccaride
38
Q

What is Streptococcus pneumoniae habitat?

A
  • Usually the upper respiratory tract
39
Q

What is streptococcus pneumonia usually treated with

A
  • penicillin G, except for meningitis which is often treated with chloramphenicol
40
Q

What do you treat streptococcus pneumoniae with when strains seem to be resistant?

A
  • vancomycin but fears that resistance will spread from enterococci
41
Q

What preventions are there from streptococcus pneumoniae and what %

A
  • Vaccine containing polysaccharide from 23 of the most prevalent types
  • Gives 75-95% protection
42
Q
A

Cellular Microbiology and Virology (17 decks)

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