Streptococci Flashcards
1
Q
What is Streptococci
A
- Streptococcus is genus of gram-positive coccus
2
Q
How does Streptococci divide?
A
- Spherical cells divide only in ONE PLAIN and form chains or pairs
3
Q
Does streptococci require complex media for growth?
A
- Yes
4
Q
What shaped cells are they?
A
- Spherical Cells (chained)
5
Q
What haem group are they unable to make ?
A
- Unable to make haem group of cytochromes or catalase
6
Q
What are Streptococci grown on ?
A
- Grown on blood agar (good source of catalase)
7
Q
What are the different groupings of Streptococci?
A
- Streptococci I: Hemolysis
- Streptococci II: Antigenically / Serologically
8
Q
What is the first grouping of Streptococcis?
A
-hemolysis
9
Q
How does Hemolysis work?
A
- Put on blood agar
- Looking into the pattern of haemolysis
10
Q
What are the different outcomes of haemolysis
A
- Beta, Alpha and Gamma hemolysis
11
Q
What is Beta haemolysis ?
A
- Complete lysis of the red blood cell
- Clear zone
12
Q
What is Alpha haemolysis?
A
- incomplete haemolysis of red blood cells
- Produce a greenish-brown zone
13
Q
What is Gamma haemolysis?
A
- no haemolysis at all
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
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
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
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
What does Glomerulonephritis lead to
- Leads to loss of protein (blood initially in urine) through kidneys and hypertension
- Can lead to chronic glomerulonephritis and kidney failure
26
What is the predominant species of Group B Lancefield?
- Streptococci agalactiae
27
What is the % of women that has S. agalactiae present on their vagina?
- 25%
28
How does S. agalactiae affect new borns
- May cause serious infections to new born
- includes high fatality rates
29
What is Group D Streptococci also known as
- Enterococci
30
What is a problem with group D Streps (Enterococci)
- Major problem of vancomycin-resistance
31
What is Streptococci viridans
- 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
- What is Streptococci mutans
- An example of Streptococci viridans species
- causes dental caries
33
How are Viridans Streptococci significant
- cause of bacterial endocarditis - infection of heart valve - invariably fatal if not treated
34
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?
- Streptococcus pneumoniae
35
How is Streptococcus pneumoniae shaped
- Lancet shaped organism.
- Usually shaped in pairs (Diplococcus)
36
How does Streptococcus pneumoniae resistant to phagocytosis
- Virulent organisms are encapsulated
37
How is Streptococcus pneumoniae subdivided
- Subdivided into 90 types on the basis of antigenicity of capsular polysaccaride
38
What is Streptococcus pneumoniae habitat?
- Usually the upper respiratory tract
39
What is streptococcus pneumonia usually treated with
- penicillin G, except for meningitis which is often treated with chloramphenicol
40
What do you treat streptococcus pneumoniae with when strains seem to be resistant?
- vancomycin but fears that resistance will spread from enterococci
41
What preventions are there from streptococcus pneumoniae and what %
- Vaccine containing polysaccharide from 23 of the most prevalent types
- Gives 75-95% protection
42
