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Medical Microbiology > Lecture 6 > Flashcards

Lecture 6 Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

What are some characteristics of Streptococcus bacteria?

A

gram+; grow in pairs/chains; catalase negative, some anaerobic and some need high amounts of CO2 to grow

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2
Q

How are streptococcus bacterium classified based on?

A

hemolytic patterns, serological reactions to cell wall antigens, DNA sequencing, metabolic/biochemical profile

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3
Q

What is the difference between enterococcus and streptococcus?

A

Enterococcus IS streptococcus! Location is different = enterococcus is in GI tract

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4
Q

How are streptococcus bacterium classified based on hemolytic patterns?

A

beta vs. alpha/gamma patterns

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5
Q

Which Streptococcus species makes a beta hemolytic pattern and which group do they belong to?

A

S. pyogenes, Group A Streptococcus (GAS)

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6
Q

Which Streptococcus species makes a beta and gamma hemolytic pattern and which group do they belong to?

A

S. agalactiae, Group B Streptococcus (GBS)

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7
Q

Which Streptococcus species makes an alpha, beta and gamma hemolytic pattern and which group do they belong to?

A

E. faecalis and E. faecium, Group D Enterococci

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8
Q

Which Streptococcus species makes an alpha hemolytic pattern and which group do they belong to?

A

S. pneumoniae, no group

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9
Q

Which hemolytic pattern signifies a negative result?

A

gamma hemolytic pattern

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10
Q

What disease are S. pyogenes associated with?

A

strep throat, wound infections, and scarlet fever

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11
Q

What diseases are S. agalactiae (GBS) associated with?

A

(“B” for “baby”) infant meningitis & pneumonia, sepsis

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12
Q

Signature disease of S. pyogenes?

A

Strep throat

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13
Q

Signature disease of S. agalactiae?

A

diseases in infants

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14
Q

What diseases are E. faecalis and E. faecium associated with?

A

UTI and bacteremia

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15
Q

Signature disease of E. faecalis/faecium?

A

UTI

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16
Q

What diseases are S. pneumoniae associated with?

A

respiratory tract infections, bacteremia, meningitis

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17
Q

Signature disease of S. pneumoniae?

A

respiratory tract infections (ie: pneumonia)

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18
Q

Where are S. pyogenes found?

A

mouth, skin, throat

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19
Q

Where are S. agalactiae found?

A

GI tract, female genital tract

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20
Q

Where are E. faecalis/faecium found?

A

colon

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21
Q

Where are S. pneumoniae found?

A

mouth and throat

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22
Q

What are the 3 modes of transmission of streptococcal diseases?

A

direct contact, aerosols, fomites

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23
Q

How do these Streptococcus microbes (found in their normal areas) cause a disease?

A

when they get to sterile parts or other parts of the body that is other than their native place

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24
Q

Characteristics of S. pyogenes?

A

spherical cocci, 1.5µm , pairs/chains, optimal growth on enriched-blood agar media, can survive on dry surfaces

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25
Q

What are more virulent S. pyogenes strains characterized by?

A

presence of a capsule

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26
Q

What are 3 identification tests for S. pyogenes?

A

catalase (–); PYR (+); bactracin susceptible (–)

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27
Q

What is strep throat (acute pharyngitis)?

A

infection of the pharynx/tonsils usually in kids less than 3yo

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28
Q

What is scarlet fever?

A

skin rash; diffuse erythematous rash starts on the chest, spreads to extremities; common in kids

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29
Q

How to test for strep throat?

A

rapid strep test

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30
Q

What are skin wound infections (pyoderma)?

A

localized infection; preshcool kids

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31
Q

What is cellulitis?

A

infection of skin involving subcutaneous tissue

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32
Q

What is necrotizing fasciitis (gangrene)?

A

deep infection of skin involving destruction of muscle/fat layers; aka “flesh-eating bacteria”; 25% mortality rate

33
Q

How does S. pyogenes cause gangrene/why can it be called a “flesh-eating bacteria”?

A

gets into subcutaneous tissue and begins to “eat away” at it = gangrene

34
Q

What is a protein that is unique to Streptococcus?

A

M-protein

35
Q

What is M-protein?

A

adhesin with anti-phagocytic activity; asissts in infection; can bind to blood proteins

36
Q

What are the hemolytic toxins S. pyogenes secrete?

A

Streptolysins S and O

37
Q

What is a group of exotoxins that S. pyogenes secrete that act as super-antigens?

A

streptococcal pyrogenic exotoxins (Spes)

38
Q

What do streptokinase exotoxins that S. pyogenes do?

A

A and B; cleave plasminogen and lyse blood clots

39
Q

What does the capsule of S. pyogenes do to act as a virulence factor?

A

hyaluronic-acid capsule = prevents phagocytosis

40
Q

What are the 2 anitbiotics prescribed against S. pyogenes?

A

penicillin and erythromycin (protein synthesis 50S inhibitor)

41
Q

Characteristics of S. agalactiae?

A

beta or non-hemolytic, asymptomatic colonization of upper respiratory tract and genitourinary tract

42
Q

What are 3 identification tests for S. agalactiae?

A

catalase (–), CAMP and hippurate hydrolysis reactions

43
Q

What would happen during child delivery if the mother has an infection in her genitourinary tract system?

A

infection can be passed onto neonate = congenital disease

44
Q

Diseases associated with S. agalactiae?

A

neonatal sepsis and meningitis post-delivery; infections acquired during pregnancy or at birth

45
Q

What virulence factors are associated with S. agalactiae??

A

polysaccharide capsule

46
Q

What 2 antibiotics are prescribed against S. agalactiae?

A

Penicillin G, and vancomycin

47
Q

Why is CAMP reaction assay the best way to identify S. agalactiae or GBS?

A

S. aureus enhances GBS hemolysis

48
Q

Characteristics of Enterococci?

A

lacks autolysin gene = penicillin only bacteriostatic in these bacteria,

49
Q

How do enterococcus species cause a UTI if they are normally found in the colon?

A

can get accidentally passed through the genitourinary tract system = cause infection

50
Q

Because enterococci strains are becoming more resistant to antibiotics, how do we go about this?

A

antibiotic combinations

51
Q

Characteristics of S. pneumoniae?

A

1 µm gram+ encapsulated diplococcus; alpha-hemolysis (aerobic) and beta-hemolysis (anaerobic)

52
Q

About how many different serotypes are there with the polysaccharide capsules of S. pneumonia?

A

~90

53
Q

What does serotypes mean?

A

composed of different antigens that will react with different antibodies due to different epitopes (on antigen)

54
Q

Why is it important to know if we have more than one different S. pneumoniae strain that reacts with different antibodies?

A

important for vaccine development; need to include different serotypes in vaccine

55
Q

What are the 5 diseases associated with S. pneumoniae?

A

otitis media, bacterial sinusitis, chronic bronchitis, bacterial pneumonia, pneuomococcal meningitis

56
Q

What is otitis media?

A

middle-ear infection in kids, self-limited disease; not serious infection and goes away w/o antibiotic interference

57
Q

What is bacterial sinusitis?

A

acute infection of the paranasal sinuses (patients of all ages)

58
Q

What is chronic bronchitis?

A

long-term inflammation of the bronchi in the lungs (supposed to be sterile = but if S. pneumoniae resides area = infection)

59
Q

What is bacterial pneumonia?

A

infection of alveoli (sterile) can result into sepsis; high death rate if not treated

60
Q

What is pneumococcal meningitis?

A

S. pneumoniae can escape respiratory tract and cause infection in the membrane that surrounds the brain; common in kids

61
Q

What species of bacteria is the cause of most respiratory tract infections?

A

S. pneumoniae

62
Q

What are the 4 virulence factors associated with S. pneumoniae

A

pneumolysin toxin, adhesins, capsule, cell wall components (peptidoglycan and LTA)

63
Q

What does the capsule of S. pneumoniae do to act as a virulence factor?

A

anti-phagocytic activity

64
Q

What do the adhesins of S. pneuominae do to act as a virulence factor?

A

binds to IgA antibodies and inactivates them

65
Q

What do the cell wall components of S. pneumoniae do to act as a virulence factor?

A

contribute to inflammation

66
Q

What does the pneumolysin exotoxin of S. pyogenes do to act as a virulence factor?

A

forms cell pores (Type II exotoxin) contributes to lung damage

67
Q

How serious is bacterial pneumoniae?

A

500K cases/yr USA; 1M+ deaths worldwide/yr

68
Q

When do bacteria usually migrate from their original reservoir to infect another area?

A

usually when there’s another infection taking place = easier for other microbes to migrate (via macrophages) and infect

69
Q

If bacteria utilizes macrophages to migrate and spread/infect, how does the macrophages not kill these bacteria?

A

the capsule protects the bacteria well

70
Q

What is one diagnostic of S. pneumoniae damage to the lungs?

A

X-ray = helps physically see the damage of the lungs

71
Q

How can otitis media happen if S. pneumoniae resides in throat and mouth?

A

it can move up and colonize nose = gives opportunity for access to the middle ear

72
Q

What are common symptoms associated with S. pneumoniae infections?

A

severe shaking chills, high fever, productive cough w/ bloody sputum, CP (chest pain)

73
Q

What are the 5 antibiotics prescribed against S. pneumoniae?

A

penicillin, vancomycin, cephalosporins, chroramphenicol, erythromycin

74
Q

What is the pneumococcal vaccines currently in use for kids?

A

7-valent (and 13-) pneumococcal conjugative vaccine (PCV-13)

75
Q

What is the pneumococcal vaccines currently in use for adults?

A

23-valent pneumococcal polysaccharide vaccine (PPSV-23)

76
Q

When refering to the pneumococcal vaccines, what does “valent” stand for and the numbers associated with it and why?

A

stands for the different serological types since S. pneumoniae has ~90 different serological capsule types

77
Q

Why must there be a different vaccine for kids?

A

current pneumococcal vaccines uses carbohydrate as part of the antigen = kids immune systems do not yet respond to polysaccharide agents = need to attach protein to polysaccharide antigen so kids’ immune systems can recognize it

78
Q

How many doses of the PCV vaccine is required for kids?

A

4 doses within 15 months

Medical Microbiology (20 decks)

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