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MicroImmuno > Streptococcus > Flashcards

Streptococcus Flashcards

1
Q

What type of bacteria (including catalase test) is Streptococcus?

A

Gram (+) cocci organized in chains and are catalase (-).

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2
Q

What characteristics are used to further classify Streptococci?

A

Hemolytic reactions on blood agar plates, serological specificity and biochemical reactions.

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3
Q

Define Hemolysis and the 3 types of hemolysis.

A

The lysis of red blood cells caused by specific bacterial enzymes.

  1. Alpha: Partial lysis of RBCs (green discoloration round colonies
  2. Beta: Complete lysis of RBCs (clearing of agar around colonies)
  3. Gamma: No lysis of RBCs (No change in agar around colonies)
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4
Q

What serological specificities are used to classify Streptococcus?

A

A) Lancefield Grouping: Beta-hemolytic streptococcus groups based on carbohydrates present in cell wall (group A-U). Groups A,B,D are important human pathogens.

B) Polysaccharide Capsules: Used to type Strep. pheumoniae

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5
Q

How are Biochemical reactions used to classify Streptococcus?

A

Sugar fermentation, tests for presence of particular enzymes and susceptibility of organisms to chemicals/physical conditions.

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6
Q

List the order of tests to differentiate specific Streptococcus groups.

A

Gram (+) –> Catalase ( - ) –> Hemolytic (Alpha, Beta, Gamma) –> Lancefield Grouping

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7
Q

Streptococcus pyogenes is ____ -hemolytic, Lancefield group ___

A

Beta; Group A

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8
Q

What antibiotic is S. pyogenes sensitive to?

A

Bacitracin – does not grow when this antibiotic is placed near it

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9
Q

Where is S. pyogenes normally carried and what percent of carriers are asymptomatic?

A

Nasopharynx; 15-20% asymptomatic

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10
Q

How is S. pyogenes transmitted?

A

Respiratory droplets or direct contact.

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11
Q

What are the virulence factors of S. pyogenes?

A

Capsule. M protein. Extracellular Enzymes. Exotoxins.

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12
Q

What does the organism’s capsule contain and what is its function?

A

Hyaluronic acid, which prevents phagocytosis.

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13
Q

What is the function of M protein?

A

Helps organism attach to cell surface and is extremely anti-phagocytotic.

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14
Q

List the specific enzymes that S. pyogenes makes.

A

Streptolysin O & S. Hyaluronidase. Streptokinase.

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15
Q

What does hyalurodinase do?

A

Breaks down hyaluronic acid in connective tissue.

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16
Q

Name the exotoxins produced by S. pyogenes and what they cause. What is the type of disease that these 3 toxins cause?

A

Erythrogenic toxin: Scarlet Fever
Exotoxin A: Toxic Shock
Exotoxin B: Necrotizing fascilitis

All “Toxin-Mediated” Diseases.

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17
Q

What are the clinical manifestations of Group A Streptococcus infections?

A

Pyogenic infections, toxin-mediated diseases and immunologically-mediated diseases.

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18
Q

What are pyogenic infections? Give 2 examples.

A

Pus producing infections.

  1. Pharygitis
  2. Skin infections
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19
Q

Why do immunologically-mediated diseases occur?

A

From complications of pyogenic infections.

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20
Q

What are suppurative (pus forming) complications of pharyngitis?

A

Peritonsillar abcess, sinusitis and otitis (ear).

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21
Q

What are non-suppurative complications of pharyngitis?

A

Rheumatic Fever

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22
Q

What are suppurative complications of skin infections?

A

Necrotizing fasciitis, and Toxic Shock Syndrome

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23
Q

What are non-suppurative complications of skin/throat infections?

A

Acute Glomerulonephritis – inflammation of renal glomerulus

24
Q

What symptoms present during rheumatic fever and how long after pharyngeal infections with Group A streptococcus?

A

Fever, carditis and polyarthritis present 2-3 weeks after infection.

25
Q

Is Rheumatic fever caused by the pharyngeal infections with Group A streptococcus?

A

No, its caused by antibodies to self antigens (M protein cross reacting with tissue).

26
Q

What is the proper prevention and treatment for Rheumatic fever?

A

Prevent with prompt treatment of Streptococcus pharyngitis and treatment for RHD with penicillin prophylactic treatment.

27
Q

What can Rheumatic Heart Disease lead to?

A

Inflammation may lead to myocardial/endocardial damage. Damaged heart valves predisposes to bacterial endocarditis.

28
Q

What type of treatment needs to be given to patients with a history of RHD before dental/surgical procedures?

A

Prophylactic antibiotic treatment.

29
Q

What symptoms present in Acute Glomerulonephritis and how long after throat/skin infections do they occur?

A

Hypertension, edema and hematuria begin after 10-20 days of throat/skin infection.

30
Q

What is the proper prevention and treatment for Acute Glomerulonephritis?

A

No prevention available, no prophylactic treatment as recurrences are rare.

31
Q

Streptococcus agalactiae is ___-hemolytic, Lancefield group ___

A

Beta; Group B

32
Q

Which antibiotic is this organism resistant to?

A

Bacitracin

33
Q

What does this organism hydrolyze?

A

Hippurate

34
Q

Where is Streptococcus agalactiae found?

A

In the normal flora of the GI and GU tracts.

35
Q

What diseases does this organism cause?

A

Neonatal meningitis and sepsis.

36
Q

What percent of women of child bearing age carry Group B strep?

A

25%

37
Q

What percent of those women give vertical transmission to their babies? What percent of babies develop an invasive disease?

A

50%; 1-2%

38
Q

If the mother is not a carrier, what is another form of transmission of this organism?

A

Nosocomial – infected while in hospital

39
Q

What is done to prevent high risk mothers from transmitting?

A

Prophylactic antimicrobials that are are cultured at 25 weeks.

40
Q

Streptococcus pneumoniae is __-hemolytic, ___cocci

A

Alpha, diplococci

41
Q

It is sensitive to what chemical?

A

Optochin

42
Q

How many antigenically distinct types of capsular polysaccharides are there in S. pneumoniae?

A

More than 85 (meaning lots of forms for this organism to inhibit phagocytosis).

43
Q

Where is the organism normally found and in what population?

A

Normal flora of oropharynx, normally found in elderly

44
Q

What type of infection does this organism cause?

A

Respiratory tract infection (pneumonia, sinusitis, otitis) and meningitis.

45
Q

What is the treatment and prevention for this infection?

A

Penicillin (though 25% of strain is resistant now) and preventable through 2 vaccines by Capsular polysaccharides.

46
Q

Viridians Group Streptococcus is either ___ or ___ hemolytic.

A

Alpha; gamma

47
Q

Viridians Group Streptococcus is resistant to what chemical?

A

Optochin

48
Q

Is Viridians Group Streptococcus soluble or non-soluble in bile?

A

Non-soluble

49
Q

Can Viridians Group Streptococcus be grouped in Lancefield typing?

A

No

50
Q

What are the clinical manifestations of Viridians Group Streptococcus?

A

Endocarditis and dental caries

51
Q

Group D Streptococci is also called?

A

Enterococci

52
Q

Where is Enterococci located

A

In the normal enteric (gut) flora

53
Q

It is bile-esculin (+) or (-)? How can it be grown?

A

Bile-esculin (+); Growth in 6.5% NaCl

54
Q

What are the clinical manifestations of Group D Streptococci (Enterococci)?

A

Urinary tract infections. Wound infections. Endocarditis.

55
Q

How do you treat Enterococci?

A

Resistant to Penicillin, so must use Vancomycin (last resort) but can also be resistant to this drug

MicroImmuno (13 decks)

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