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Microbiology > Streptococcus Species > Flashcards

Streptococcus Species Flashcards

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Biology 101 flashcards
1
Q

Are streptococci gram - or gram +

A

gram +

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2
Q

Define beta-hemolysis

A

complete lysis of RBCs with a zone of clearing. It is usually due to cytolytic toxins.

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3
Q

Define alpha-hemolysis

A

Incomplete lysis of the RBC with a zone of “greening” or darkening

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4
Q

What is unique about alpha-hemolysis

A

It is only seen with streptococci

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5
Q

Define gamma-hemolysis

A

no hemolytic reaction

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6
Q

Group A Strep Species

A

S. pyogenes

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7
Q

Group D Strep Species

A

Enterococci

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8
Q

Group A Strep: type of hemolysis

A

beta

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9
Q

Group D Strep: type of hemolysis

A

alpha, beta, and gamma

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10
Q

Describe the taxonomy of streptococci

A

Gram + cocci that occur in pairs or chains. They are strictly fermentative/anaerobic and they are catalase -.

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11
Q

Virulence Factors of Group A Strep (7 important ones)

A
  1. All the cell wall stuff
  2. M protein
  3. Protein G
  4. Capsule
  5. Exotoxins! (lots of them, see other flashcards/notes for specific)
  6. Pyrogenic exotoxins
  7. Exo-enzymes
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12
Q

What are the two cytolytic exotoxins of Group A strep

A

Streptolysin O and Streptolysin S.

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13
Q

Streptolysin O

A

cytolytic exotoxin of group A strep that is oxygen labile

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14
Q

Streptolysin S

A

cytolytic exotoxin of group A strep that is oxygen stable

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15
Q

Do all group A produce Spe (pyrogenic exotoxins)?

A

No. They only produce it if they have the bacteriophage carrying the gene

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16
Q

Spe

A

pyrogenic exotoxin produce in some group A strep. These are super antigens that are very inflammatory. They are erythrogenic toxins that cause rash and fever of scarlet fever.

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17
Q

Transmission of Group A strep

A
  • respiratory droplets
  • exchanging secretions
  • adult intermediate carrier
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18
Q

What age group is primarily affected by Group A strep?

A

5-15 yo

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19
Q

Who is especially susceptible to invasive Group A Strep disease

A

people with chronic illness and those who use medications such as steroids

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20
Q

What are the most common acute group A strep infections?

A

Pharyngitis, scarlet fever, invasive disease/pneumonia, skin and soft tissue infections.

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21
Q

Complications of pharyngitis “strep throat”

A

Tonsillar abscess, otitis media, septicemia, osteomyelitis, and endocarditis

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22
Q

Scarlet Fever

A

Strep throat that is complicated by the production of pyrogenic exotoxin. It is a local infection with systemic toxemia.

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23
Q

Symptoms of scarlet fever

A

characteristic rash beginning on the face, and neck spreading to the trunk and extremities, blanches on pressure. Desquamation may occur after 4 days.

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24
Q

Can group A strep cause bloodstream invasions?

A

YES. Can lead to sepsis and endocarditis.

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25
Q

What are the 3 sequelae of Group A Strep?

A

Acute Rheumatic Fever, Acute glomerulonephritis, and PANDAS

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26
Q

Describe Acute Rheumatic Fever

A

Inflammatory rx that occurs only 2-3 weeks after a group A strep pharyngitis. Hyperimmune response to streptococcal antigens that cross react with host tissue.

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27
Q

What population is most affected by acute rheumatic fever

A

Age 5-15, poorer populations

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28
Q

Symptoms of Acute Rheumatic Fever

A

Multi-system disorder of vague symptoms. Carditis, arthritis, erythematous skin lesions, subcutaneous nodules.

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29
Q

Describe acute glomerulonephritis

A

Kidney inflammation after a prior group A strep pharyngitis OR a skin infection.

30
Q

What population is most affected by acute glomerulonephritis?

A

children, primarily 5-15 yo

31
Q

Pathogenesis of acute glomerulonephritis

A

Deposition of immune complexes in the kidney, leading to inflammation.

32
Q

What is PANDAS?

A

Pediatric Autoimmune Neuropsychiatric Disorder Associated with group A beta-hemolytic streptococci. Appears to be an inappropriate immune response to Group A strep.

33
Q

Symptoms of PANDAS

A

development of sudden OCD and related symptoms following a Group A Strep infection

34
Q

5 diagnostic criteria of PANDAS

A
  1. OCD and/or tic disorder along w/ mood swings, anxiety attacks, and ADHD symptoms
  2. Onset between 3 years and puberty
  3. Abrupt onset or episodic course of symptoms
  4. Temporal relationship between strep infection and neuropsychiatric exacerbation
  5. Tic or other neurologic abnormalities during exacerbation
35
Q

Lab Diagnosis of Streptococci

A

-Gram Stain from sterile sites
-Antigen detection kit of throat swab
-Culture for 24 hr observing for beta-hemolytic rxn
=Serology for anti-strepsolysin O and Anti-DNAse B

36
Q

Are there vaccines for streptococci?

A

NO! There is a risk for cross reaction with the host

37
Q

Group B strep transmission

A

Normal flora of the vagina so it is transmitted to the newborn during vaginal deliver.

38
Q

Diseases caused by Group B strep?

A

Neonatal meningitis, neonatal pneumonia, bacteremia

39
Q

Virulence factors for Group B strep

A

Polysaccharide capsule

Hemolysin/cytolysin

40
Q

Prevention of neonatal meningitis/pneumonia;

A

screen pregnant women with antigen detection kit via vaginal swab. May use PCN prophylaxis or C section if +.

41
Q

Group D Streptococcus: Enterococcus Primarily Disease

A

Nosocomial problem for people in hostile

42
Q

Diseases caused by Group D Strep

A

UTI, intra-abdominal abscess, wound infection, septicemia, endocarditis

43
Q

Group D Strep Treatment

A

BIG PROBLEM. Often resistant to PCN and ampicillin. Increasing VRE.

44
Q

Is the Lancfield Classification used for alpha or beta hemolytic strep?

A

Only used to classify beta hemolytic

45
Q

Diseases caused by strep. pneumoniae

A

Pneumonia, meningitis, otitis media, sinusitis, conjunctivitis (URTIs)

46
Q

What are the risks of strep. Viridans getting into the bloodstream?

A

Subacute endocarditis, prosthetic join infection, abscess formation in brain, liver, lung and abdomen.

47
Q

Taxonomy of strep. pneumonia

A

Gram + alpha hemolytic lancet shaped diplococci

48
Q

Virulence factors of strep. pneumonia

A
  • Cell wall antigens
  • Capsule
  • Exotoxins and enzymes
49
Q

What are the exotoxins of strep pneumonia

A

pneumonlysin

50
Q

Describe the activity of pneumolysin

A

Exotoxin of strep pneumonia that is oxygen labile, cross reacts withs streptolysin O and kills phagocytes.

51
Q

Transmission of strep pneumonia

A

spread of normal flora from naso/oropharynx to adjacent tissue or aspiration into the lungs.

52
Q

What populations are especially susceptible to strep pneumonia?

A
  1. infants and children-superficial URT infection

2. very young and elderly, or anyone with underlying disease-invasive infections

53
Q

Symptoms of pneumonia caused by strep pneumonia

A

Rapid onset
shaking chills
fever
developing cough with rusty sputum

54
Q

Complications of pneumonia caused by strep pneumonia

A

Pleural effusion + empyema
Bacteria with meningitis
Bacteremia complications: endocarditis, pericarditis, septic arthritis

55
Q

What is the most common cause of meningitis in adults

A

bacteremia with meningitis caused by strep pneumonia

56
Q

What is the most common cause of otitis media?

A

Strep pneumonia

57
Q

Lab diagnosis of strep pneumonia

A
  • Gram stain of CSF or sputum
  • Urine antigen test
  • Antigen detection in CSF
  • Culture on blood agar to observe for alpha hemolysis and mucoid colonies
58
Q

Should antibiotic sensitivities be tested in strep pneumonia?

A

YES. All isolates must be tested for resistance to PCN due to rapidly emerging resistant strains

59
Q

Treatment of otitis media caused by strep. pneumonia?

A

Amoxicillin (PO)

60
Q

Treatment of conjunctivitis caused by strep. pneumonia?

A

Fluoroquinolones

61
Q

Treatment for pneumonia, meningitis, and endocarditis caused by strep pneumonia

A

PCN G (IM or IV)

62
Q

What is the antibody target of the strep pneumonia vaccine?

A

The capsule

63
Q

What was the original vaccine of strep pneumonia?

A

PPV, Pneumovax 23

64
Q

When is pneumovax 23 used?

A

It is not used in children <2 yo because there is no response. it works well in adults and is still used.

65
Q

What is the conjugate vaccine for strep pneumonia

A

PCV-7, Prevnar 7

66
Q

Why is the conjugate vaccine useful in children?

A

The infant processes the protein antigen with the attached polysaccharide and makes antibodies against both?

67
Q

How is the Prevnar 7 vaccine made?

A

The purified polysaccharide from 7 of the most common serotypes is conducted to a protein.

68
Q

What is the vaccine schedule for Prevnar 7?

A

infants receive dose at 2, 4, and 6 months followed by booster at 12-15 mos.

69
Q

What is PCV-13/Prevnar 13?

A

Is is a new vaccine that has an additional 6 new purified polysaccharides to cover serotypes that were not part of the Prevnar 7 vaccine.

70
Q

What condition/disease has Prevnar 13 been approved for?

A

Otitis Media! Remember that strep pneumonia is the most common cause!

Microbiology (13 decks)

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