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Exam 2 MIM Microbiology > Clinical Bacteriology I & II > Flashcards

Clinical Bacteriology I & II Flashcards

1
Q

What is a biofilm?

A

A bacterial community

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2
Q

What is a consortium?

A

Another term for a community of bacteria

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3
Q

What are the two phyla of bacteria which are predominant in the GI tract?

A

1) firmicutes

2) bacteroidetes

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4
Q

What are some characteristics of bacteria present in biofilms?

A

1) grow slower
2) more abx resistant
3) might use different metabolic pathways
4) more diverse

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5
Q

What surface on the human body demonstrates biofilms most readily?

A

teeth!

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6
Q

What are the five steps in the biofilm lifecycle?

A

1) adhesion
2) colonization
3) accumulation
4) climax community
5) dispersal

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7
Q

What determines whether a biofilm will grow in a certain environment?

A

whether the surface is shedding or non-shedding

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8
Q

On what clinical surfaces would you find biofilms?

A

1) orthopedics
2) catheters
3) hospital equipment

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9
Q

What two micriobiological diagnostic tools can physicians use?

A

1) staining and cultured growth

2) abx sensitivity tests

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10
Q

What is a substratum?

A

surface for bacterial colonization

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11
Q

What is a pioneer?

A

the first bacterial colonizers

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12
Q

What are two non-culturable bacteria?

A

1) treponema

2) mycobacterium leprae

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13
Q

What are the factors that we need to grow bacteria from a clinical specimen?

A

1) temperature
2) ph
3) gaseous requirements
4) minerals, trace elements, and vitamins
5) nitrogen and carbon sources
6) energy generation

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14
Q

What are five categories of bacteria by gaseous requirements?

A

1) obligate aerobes
2) microaerophiles
3) capnophiles
4) facultative anaerobes
5) obligate anaerobes

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15
Q

What is unique about obligate aerobes?

A

They NEED oxygen in order to survive

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16
Q

What is unique about microaerophiles?

A

They are inhibited by oxygen content, but will not be killed by increased oxygen

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17
Q

What is unique about capnophiles?

A

They grow best in hypercapnic conditions

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18
Q

What is unique about facultative anaerobes?

A

they can grow in all oxygen environments

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19
Q

What is unique about obligate anaerobes?

A

They cannot grow in any oxygen environment and exposure to oxygen kills the cells

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20
Q

What is dysbiosis?

A

Microbial imbalance in the “normal” microbiota of the body

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21
Q

Which group of bacteria is the most medically important?

A

facultative anaerobes

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22
Q

For what purpose is liquid media used to select bacteria?

A

It is used to culture bacteria that are from usually sterile sites and which there will generally be a monoculture.

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23
Q

For what purpose is solid media used to select bacteria?

A

It is used for all other populations of bacteria and dilution and separation of the bacteria of interest can be more easily obtained

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24
Q

Outline the blood culture technique.

A

Take a small amount of blood and inject it into multiple “blood bottles” over time intervals. You take it at different times and different places to minimize risk of contamination

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25
Q

What are the four phases of the bacterial growth curve?

A

1) lag
2) log
3) stationary
4) death

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26
Q

What is the lag phase?

A

Time where growth is minimal as the bacteria adapt to the host.

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27
Q

What is the log phase?

A

Time where bacteria grow the fastest. This is where signs and symptoms appear and you get tissue destruction

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28
Q

What is the stationary phase?

A

The growth of bacteria is offset by the their death facilitated by phagocytosis with antibodies

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29
Q

What is the death phase?

A

This is where bacteria are cleared from the system

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30
Q

At what point will a spore-forming bacteria sporulate?

A

At the inflection point between the log phase and the stationary phase

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31
Q

In which phase is a bacteria most susceptible to antibiotics?

A

The log phase because the bacteria are the most metabolically active

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32
Q

What are the five techniques in which to identify bacteria in the “clin lab”?

A

1) direct microscopic identification
2) antigen detection/serology
3) cell component detection - chemical/biochemical analysis
4) molecular diagnosis
5) culture

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33
Q

What are the two main microscopic morphologies?

A

1) cocci

2) rods (bacilli)

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34
Q

What is the Gram’s stain?

A

The Gram’s stain will test for the presence of a particular cell wall and separate bacteria into gram-positive and gram-negative

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35
Q

What are the steps of the Gram’s stain procedure?

A

1) dye with crystal violet
2) dye with iodide
3) decolorize with ethanol
4) counterstain with safranin

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36
Q

What are the six bacteria which can cause bacterial meningitis?

A

1) strep pneumoniae
2) strep agalactiae
3) listeria monocytogenes
4) neisseriea meningitidis
5) escherichia coli
6) haemophilus influenza

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37
Q

What is a primary cause of neonatal sepsis?

A

strep agalactiae

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38
Q

Which bacteria can cross the placental barrier?

A

listeria monocytogenes

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39
Q

What does the acid-fast stain stain for?

A

Mycobacterium

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40
Q

How do you know you have an acceptable sputum culture?

A

Presence of PMNs

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41
Q

What are the three groups of solid media?

A

1) general purpose
2) differential or partially selective
3) selective

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42
Q

What is chocolate agar?

A

Agar plated with RBCs that have become lysed

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43
Q

What is chocolate agar used for?

A

Fastidious bacteria such as H. influenzae which need particular conditions

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44
Q

What is sheep’s blood agar?

A

An agar-based plate with 5% sheep’s blood whose RBCs are plated intact

45
Q

What is unique about blood agar plates?

A

Because the RBCs are intact, it can show specific strains of bacteria which are hemolytic

46
Q

What is beta hemolysis?

A

This is complete hemolysis which goes through the full width of the plate

47
Q

What is alpha hemolysis?

A

This is the discoloration of RBCs but incomplete lysis usually due to production of hydrogen peroxide

48
Q

Why are differential plates also called partially selective plates?

A

Because they select for some strains by suppressing the growth of particular strains. And they dye others to separate strains by some type of quality (“differential”)

49
Q

What is MacConkey Agar?

A

This inhibits the growth of Gram positive bacteria, while selecting for growth of lactose fermenters which will dye the media

50
Q

What pathogens does MacConkey Agar select for?

A

Enteric pathogens

51
Q

What is a selective media?

A

That which combines a solid media with both antifungals and certain antibiotics

52
Q

What is a type of selective media?

A

Thayer-Martin agar

53
Q

What does Thayer-Martin agar select for?

A

It is particular good at selecting for neisseria strains, as they are sometimes found in populations which have yeast or other mixed populations which might make them otherwise hard to isolate

54
Q

What defines a bacterial colony?

A

it is a clonal population that has grown out of one bacteria

55
Q

What are three ways to identify different colony morphologies?

A

1) form
2) elevation
3) margin

56
Q

What do most antibiotics targets?

A

cell wall assembly

57
Q

What functions have the cell wall replaced in the prokaryotic cell?

A

organelles

58
Q

What is the major constituent of the cell wall?

A

peptidoglycan

59
Q

What does the cell membrane of a prokaryote lack which cell membranes of eukaryotes have?

A

cholesterol

60
Q

What is the only organelle that prokaryotes do have?

A

ribosome

61
Q

Which two species of bacteria have no cell wall?

A

mycoplasma and ureaplasma

62
Q

What do the plasma membranes of mycoplasma and ureaplasma have to make up for having no cell wall?

A

sterols

63
Q

What are the different strategies which bacteria use to counteract their hosts?

A

1) adherence
2) anti-complementary
3) anti-phagocytic
4) mechanisms to subvert humoral immunity
5) mechanisms to subvert cellular immunity
6) production of exo- and endotoxins

64
Q

Pili, fimbriae, and the bacterial capsule are all pathogenic strategies of?

A

adherence

65
Q

The capsule of a protein serves which purposes for host-pathogen interaction?

A

1) adherence
2) anti-complement
3) anti-phagocytic

66
Q

What are proteases particularly useful for in defense of a bacterium?

A
  • degradation of complement proteins

- degradation of immunoglobulins

67
Q

What are specific mechanisms which bacteria use to subvert humoral immunity?

A

Fc receptors, Ig proteases, endotoxins, LPS/LTA, cell wall

68
Q

To what two antigens do we develop vaccines?

A

1) capsule

2) endotoxins

69
Q

Where is the capsule located?

A

most externally located

70
Q

What are two other names for the capsule?

A

1) slime

2) glycocalyx

71
Q

What is a capsule typically made of?

A

polysaccharides

72
Q

What is the exception to polysaccharide capsules?

A

Bacillus, which uses a proteinaceous capsule

73
Q

What is capsule termed in gram negative bacteria?

A

K antigen

74
Q

How is a capsule antigenically diverse?

A

It might have a lot of different types of antigenic capsules expressing different antigens or combinations of such

75
Q

What are examples of virulence factors?

A

1) flagella
2) capsule
3) toxins
4) adhesive proteins

76
Q

What are flagella termed in gram negative bacteria?

A

H antigen

77
Q

How are flagella driven?

A

proton-motive force

78
Q

What is a flagellum composed of?

A

helically arranged flagellin

79
Q

What was the original distinction between those bacteria which had fimbriae and those which had pili?

A

Gram positive bacteria had fimbriae. Gram negative bacteria had pili.

80
Q

What is it termed when a structure can be “turned” on and off?

A

phase variation

81
Q

Flagella, fimbriae, and pili are all examples of what, in terms of immunity?

A

MAMPs

82
Q

How do pili exert tropism for a particular tissue?

A

act as lectins in that they bind only to specified sugar moieties

83
Q

What is the structure of the bacterial cell wall?

A

NAM and NAG disaccharide backbone with tetrapeptide cross-linkages

84
Q

What are Gram-negative bacteria lacking in their peptidoglycan?

A

cross linkages between tetrapeptides

85
Q

From which sugar does the tetrapeptide come off of in peptidoglycan?

A

N-acetylmuramic acid

86
Q

What amino acid does the tetrapeptide begin and end with?

A

alanine

87
Q

What is the third amino acid in the tetrapeptide sequence?

A

always a di-amino acid

88
Q

What is the name of the antigen that is recognized by PRRs in peptidoglycan?

A

muramyl dipeptide

89
Q

What do mycobacteria add to their cell wall?

A

layers of mycolic acid

90
Q

What is the difference between lipoteichoic and teichoic acid?

A

Teichoic acid is covalently linked to cell wall.

91
Q

To what is lipoteichoic acid tethered?

A

Plasma membrane due to a lipid chain

92
Q

What are the purposes of LTA/TA?

A

capturing cations and maybe adhesion

93
Q

Why is LTA/TA like the LPS in Gram - bacteria?

A

it is highly pro-inflammatory

94
Q

What immune responses does LPS elicit?

A

-polyclonal B cell activation

95
Q

How does LPS elicit an immune response?

A

acts as a potent MAMP and is recognized by CD14 and TL4

96
Q

What is LPS composed of?

A

1) lipid A
2) core polysaccharide
3) O polysaccharide

97
Q

What is O polysaccharide also called?

A

somatic antigen

98
Q

What function does the outer membrane of Gram-negative bacteria function as?

A

1) effective barrier
2) molecular sieve
3) attachment site for adhesion
4) pathogenic determinants

99
Q

What is the layer which contains peptidoglycan called in Gram negative bacteria?

A

periplasmic space

100
Q

What are the outer membrane components of E.coli?

A

LPS and porins

101
Q

What is the periplasmic space used as?

A

1) area of import/export

2) area for hydrolytic enzymes

102
Q

What is most extrachromosomal DNA in a bacterium?

A

plasmids

103
Q

What do plasmid genes confer?

A

selective advantage

104
Q

What type of proteins are used in the transeptal processes in binary fission?

A

cytoskeletal proteins

105
Q

What can be in inclusion granules?

A

polyphosphate, glycogen/starch, and lipid

106
Q

What are the only medically relevant bacteria which produce spores?

A

Gram-positive rods (Clostridium and Bacillus)

107
Q

What is the difference between Clostridium and Bacillus?

A

Clostridium is gram-negative whereas Bacillus is gram-positive

108
Q

At what point do these species usually produce spores?

A

In late log phase. usually when there is a limitation of the amino acid alanine

Exam 2 MIM Microbiology (5 decks)

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