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Microbiology > Streptococcus Species > Flashcards

Streptococcus Species 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
What are the 3 sequelae of Group A Strep?
Acute Rheumatic Fever, Acute glomerulonephritis, and PANDAS
26
Describe Acute Rheumatic Fever
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.
27
What population is most affected by acute rheumatic fever
Age 5-15, poorer populations
28
Symptoms of Acute Rheumatic Fever
Multi-system disorder of vague symptoms. Carditis, arthritis, erythematous skin lesions, subcutaneous nodules.
29
Describe acute glomerulonephritis
Kidney inflammation after a prior group A strep pharyngitis OR a skin infection.
30
What population is most affected by acute glomerulonephritis?
children, primarily 5-15 yo
31
Pathogenesis of acute glomerulonephritis
Deposition of immune complexes in the kidney, leading to inflammation.
32
What is PANDAS?
Pediatric Autoimmune Neuropsychiatric Disorder Associated with group A beta-hemolytic streptococci. Appears to be an inappropriate immune response to Group A strep.
33
Symptoms of PANDAS
development of sudden OCD and related symptoms following a Group A Strep infection
34
5 diagnostic criteria of PANDAS
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
Lab Diagnosis of Streptococci
-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
Are there vaccines for streptococci?
NO! There is a risk for cross reaction with the host
37
Group B strep transmission
Normal flora of the vagina so it is transmitted to the newborn during vaginal deliver.
38
Diseases caused by Group B strep?
Neonatal meningitis, neonatal pneumonia, bacteremia
39
Virulence factors for Group B strep
Polysaccharide capsule | Hemolysin/cytolysin
40
Prevention of neonatal meningitis/pneumonia;
screen pregnant women with antigen detection kit via vaginal swab. May use PCN prophylaxis or C section if +.
41
Group D Streptococcus: Enterococcus Primarily Disease
Nosocomial problem for people in hostile
42
Diseases caused by Group D Strep
UTI, intra-abdominal abscess, wound infection, septicemia, endocarditis
43
Group D Strep Treatment
BIG PROBLEM. Often resistant to PCN and ampicillin. Increasing VRE.
44
Is the Lancfield Classification used for alpha or beta hemolytic strep?
Only used to classify beta hemolytic
45
Diseases caused by strep. pneumoniae
Pneumonia, meningitis, otitis media, sinusitis, conjunctivitis (URTIs)
46
What are the risks of strep. Viridans getting into the bloodstream?
Subacute endocarditis, prosthetic join infection, abscess formation in brain, liver, lung and abdomen.
47
Taxonomy of strep. pneumonia
Gram + alpha hemolytic lancet shaped diplococci
48
Virulence factors of strep. pneumonia
- Cell wall antigens - Capsule - Exotoxins and enzymes
49
What are the exotoxins of strep pneumonia
pneumonlysin
50
Describe the activity of pneumolysin
Exotoxin of strep pneumonia that is oxygen labile, cross reacts withs streptolysin O and kills phagocytes.
51
Transmission of strep pneumonia
spread of normal flora from naso/oropharynx to adjacent tissue or aspiration into the lungs.
52
What populations are especially susceptible to strep pneumonia?
1. infants and children-superficial URT infection | 2. very young and elderly, or anyone with underlying disease-invasive infections
53
Symptoms of pneumonia caused by strep pneumonia
Rapid onset shaking chills fever developing cough with rusty sputum
54
Complications of pneumonia caused by strep pneumonia
Pleural effusion + empyema Bacteria with meningitis Bacteremia complications: endocarditis, pericarditis, septic arthritis
55
What is the most common cause of meningitis in adults
bacteremia with meningitis caused by strep pneumonia
56
What is the most common cause of otitis media?
Strep pneumonia
57
Lab diagnosis of strep pneumonia
- 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
Should antibiotic sensitivities be tested in strep pneumonia?
YES. All isolates must be tested for resistance to PCN due to rapidly emerging resistant strains
59
Treatment of otitis media caused by strep. pneumonia?
Amoxicillin (PO)
60
Treatment of conjunctivitis caused by strep. pneumonia?
Fluoroquinolones
61
Treatment for pneumonia, meningitis, and endocarditis caused by strep pneumonia
PCN G (IM or IV)
62
What is the antibody target of the strep pneumonia vaccine?
The capsule
63
What was the original vaccine of strep pneumonia?
PPV, Pneumovax 23
64
When is pneumovax 23 used?
It is not used in children <2 yo because there is no response. it works well in adults and is still used.
65
What is the conjugate vaccine for strep pneumonia
PCV-7, Prevnar 7
66
Why is the conjugate vaccine useful in children?
The infant processes the protein antigen with the attached polysaccharide and makes antibodies against both?
67
How is the Prevnar 7 vaccine made?
The purified polysaccharide from 7 of the most common serotypes is conducted to a protein.
68
What is the vaccine schedule for Prevnar 7?
infants receive dose at 2, 4, and 6 months followed by booster at 12-15 mos.
69
What is PCV-13/Prevnar 13?
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
What condition/disease has Prevnar 13 been approved for?
Otitis Media! Remember that strep pneumonia is the most common cause!

Microbiology (13 decks)

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