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Microbiology > Bacteria > Flashcards

Bacteria Flashcards

1
Q

what is s. aureus an example of

A

a classic pathogen

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2
Q

what does s. aureus cause

A

oral diseases such as angular cheilitis, mucositis and bone infection

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3
Q

what is angular cheilitis

A

inflammation of the corners of the mouth

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4
Q

what is the pathway following suspected infection of s. aureus causing angular cheilitis

A
  • sample with a sterile swab moistened with sterile water
  • rub swab on blood agar
  • incubate the bacteria at an appropriate temperature
  • look at the colony morphology to identify s. aureus
  • can then do a gram stain, and look at the clumping factor detection
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5
Q

how does s. aureus appear on gram stains

A

as black dots, resembling very closely to a bunch of grapes

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6
Q

what does s. aureus contain that allows it to clump in serum

A

coagulase positive virulence factor

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7
Q

what is an example of non selective agar

A

blood agar

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8
Q

what are the benefits of using blood agar

A

grows everything on the sample, which can give a good overal impression of the bacteria

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9
Q

what are the negatives of using blood agar

A

grows everything which can make it difficult to pick out pathogens of interest

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10
Q

what is an example of selective agar - in the context of s. aureus

A

mannitol salt agar

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11
Q

what do the elements of mannitol salt agar involve

A

the mannitol is a sugar that when fermented changes pH and can indicate the presence of s. aureus. the salt inhibits the growth of lots of different types of bacteria while still allowing s. aureus to grow if you play around with the concentration.

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12
Q

how is s. aureus characterised

A

its clumpy grape gram stain appearance

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13
Q

what is the process of testing the presence of s. aureus in a sample on mannitol salt agar

A
  • the salt suppresses the growth of other bacteria beside s. aureus
  • s. aureus ferments mannitol, which lowers the pH within the agar, making it acidic
  • the pH indicator in the mannitol salt agar changes the colour of the agar from pink to yellow
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14
Q

what other species of staph are there

A

s. epidermis

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15
Q

how can you differentiate between s. aureus and s. epidermis.

A

s. epidermis does not ferment mannitol and therefore will not change the colour of the agar. s. epidermis also lacks the coagulent factor and will not clump in serum, whereas the s. aureus will.

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16
Q

how can colony morphology aid in the identification of s. aureus

A

when s. aureus is present it has a round, convex shape and can also be characterised by its size and sharp odor

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17
Q

what is found on the cell wall of s. aureus

A

clumping factor and protein A

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18
Q

break down the name of s. aureus

A

staphyloccocus aureus
- staphyl is the genus, and is related to the grape shape it adopts on gram stains
- coccus is related to the round shape
- aureus is related to the gold colour on blood agar

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19
Q

is s. epidermis coagulase negative or coagulase positive

A

coagulase negative

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20
Q

what is another antimicrobial testing method that can be used to identify presence of s. aureus

A

minimum inhibitory concentration

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21
Q

what is minimum inhibitory concentration

A

measures how much antibiotic is required to inhibit the bacteria - helps with prescribing

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22
Q

what does minimum inhibitory concentration highlight the importance of

A

taking specimens for identification and susceptibility training

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23
Q

what is present in mannitol salt agar that presents a colour change

A

pH indicator

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24
Q

what changes the pH in mannitol salt agar

A

the fermentation of the mannitol by the s. aureus

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25
Q

what is a bacterial endotoxin

A

toxic substances bound to the bacterial cell wall that are released when the bacterium ruptures or disintegrates

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26
Q

how do prions lead to a spongiform appearance in the affected brain

A

they affect signalling processes, damaging neurons and leading to the spongiform

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27
Q

what is spongiform encephalopathy

A
  • spongiform = sponge like. brain tissue degenerates, where the healthy tissue become cysts and the brain looks like a sponge.
  • encephalo (brain) pathy (disease process) - cause is the accumulation of misfolded proteins called prions
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28
Q

what are prions

A

misfolded proteins

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29
Q

what does fomite mean

A

objects or materials which are likely to carry infection, such as clothes, utensils, and furniture

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30
Q

what does SICP stand for

A

standard infection control precautions

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31
Q

what is the ecological plaque hypothesis used to explain

A

the disease process for caries and periodontal disease

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32
Q

what is the ecological plaque hypothesis

A

a theory that dental plaque induced diseases are not caused by specific species, but by changes in the environment that lead to an imbalance in the normal oral microflora

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33
Q

break down the ecological plaque hypothesis

A
  • stress such as increased sugar intake leads to increased acid production
  • this leads to an environmental shift, where the neutral pH falls to a lower pH level
  • this changes the ecological environment, which leads to disease, like caries
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34
Q

what does the understanding of the difference between host and bacterial cells also help with

A

insight into disease diagnosis and treatment

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35
Q

what are the key anatomical elements to bacterial cells

A
  • outer capsule and protective layers
  • other bacterial components
  • genome, which is a circular strand of DNA
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36
Q

what are examples of virulence factors

A

fimbriae, pili, fibrillae, and colonisation factors

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37
Q

what is virulence

A

the severity or harmfulness of a disease

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38
Q

what contributes to how harmful a disease is

A

adhesion and antiphagocytics

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39
Q

what are the first steps in pathogenesis

A

exposure and adhesion

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40
Q

what is an adhesin

A

a protein or glycoprotein found on the surface of a pathogen that attaches to receptors on the host cell

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41
Q

what pathogen causes dental caries

A

streptococcus mutans

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42
Q

what is the adhesin of s. mutans

A

adhesin p1

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43
Q

where does adhesin p1 attach to

A

teeth

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44
Q

what is chemotaxis

A

the movement of an organism or entity in response to chemical stimulus

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45
Q

what does aerobic bacteria require

A

oxygen

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46
Q

what does capnophilic bacteria require

A

carbon dioxide

47
Q

what does facultative bacteria require

A

with and without oxygen

48
Q

what does anaerobic bacteria require

A

no oxygen

49
Q

what does microaerophilic bacteria require

A

small amounts of oxygen

50
Q

how do bacteria grow

A

binary fission

51
Q

what does binary fission describe

A

the way in which bacteria grow

52
Q

what is another way of describing the way in which bacteria grow

A

exponential growth

53
Q

what illustrates binary fission of bacteria

A

cell number growth curves

54
Q

what are the different phases of a growth curve of bacteria

A
  • lag phase
  • exponential growth phase
  • stationary phase
  • death curve
55
Q

what occurs in the lag phase

A

the bacteria are inoculated into a system, and the bacteria acclimatise to their new surroundings

56
Q

what occurs in the exponential growth phase

A

binary fission - rapid reproduction of bacteria

57
Q

when is it thought that exponential growth occurs in the body

A

during infection

58
Q

what is the stationary phase

A

this is when production is equal to death

59
Q

what is the death curve

A

this is when the bacteria death rate is greater than bacterial reproduction

60
Q

what is managing infection about in regards to the cell number growth curve

A

discourgaing the growth phase and encouraging the death curve

61
Q

what is the purpose of a gram stain

A

visualising bacteria

62
Q

why do we not just use a microscope to visualise bacteria

A

the bacteria are too thin and the light will shine right through them

63
Q

why can gram stains be used if someone is infected

A

if you look at the specimen using special stains under the microscope to visualise the bacteria, you can then make a judgement call on the best antibiotic to use for treatment

64
Q

what are the different classifications of bacteria in gram stains

A

gram positive and gram negative

65
Q

what is within the cell wall material of gram positive cells that allows the crystal violet dye to stick

A

peptidoglycan

66
Q

how are bacteria classified as being either gram positive or gram negative

A

based on the difference in the structure of their peptidoglycan cell wall

67
Q

what is the main role of peptidoglycan

A

gives strength to the outer structure of the organism

68
Q

how is peptidoglycan vital for binary fission

A

when the bacteria divide themselves into two, the peptidoglycan in the cell wall must grow as the bacterium elongates before dividing. and then when it has split, the cell wall must reform so the two new cells are both enclosed

69
Q

what is the series of events of using a gram stain to visualise bacteria

A
  • specimen added to film
  • chemical called crystal violet is added to film
  • all cells take up the dye
  • flood film with lugols iodine
  • all cells appear blue black
  • decolourise with acetone
  • gram pos cells retain dye complex
  • gram neg cells are decolourised
  • counterstain with a red dye
  • gram pos appear blue black
  • gram neg appear red
70
Q

how do penicillin binding proteins link to the importance of peptidoglycan and gram positive cells

A

PBP are enzymes involved in the cross linking of the peptidoglycan layer of the cell wall

71
Q

how do penicillin binding proteins link with antibiotics

A

they are targets for penicillin based antibiotics and stop further linking of peptidoglycan side chains

72
Q

what are exotoxins

A

toxins secreted by bacteria. they are produced by both gram pos and gram neg bacteria

73
Q

what exotoxin is produced by clumps of s. aureus

A

panton valentine leukocidin - kills white blood cells

74
Q

what do high concentrations of panton valentine leukocidin cause

A

pmn lysis

75
Q

what does pmn lysis mean

A

polymophonuclear leukocytes are phagocytes that consume s. aureus, but some s. aureus strains are able to cause lysis of these cells after being consumed

76
Q

what is the issue with PMN lysis

A

causes an inflammatory response and eventually tissue necrosis (cell death)

77
Q

what is an example of an endotoxin

A

lipopolysaccharides

78
Q

what are lipopolysaccharides

A

large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. they are potent biochemical molecules

79
Q

what is the clinical relevance of endotoxins

A

they cause localised disease like chronic periodontitis and can trigger sepsis

80
Q

what does cocci mean

A

round shaped

81
Q

what does bacilli mean

A

rod shaped

82
Q

why are spiral forms of bacteria of dental relevance

A

cause acute ulcerative gingivitis

83
Q

why are spiral forms of bacteria difficult to visualise using conventional gram staining

A

they have very thin cell walls

84
Q

what kind of bacteria is an exception to gram stains

A

mycobacteria - they have a thick, waxy cell wall whcih makes gram stains difficult to penetrate

85
Q

how can mycobacteria be visualised

A

using fluorescent microscopy

86
Q

what is a clinical example of mycobacteria

A

the mycobacteria abscessus infection that had an outbreak in georgie in a dental practice to children who had a pulpotomy. it was caused by contaminated water being used during the pulpotomies

87
Q

what is m. abscessus

A

a rapidly growing, non tuberculosis mycobacterium found in the environment in water, soil and dust

88
Q

what is an example of a gram positive cocci bacteria

A

streptococcus mutans, which occur in chains and cause dental caries

89
Q

what is an example of a gram positive bacilli bacteria

A

clostridium tetani which has a rice shape and causes spinal contraction

90
Q

what is an example of a gram negative cocci bacteria

A

diplococci antiphagocytic such as neisseria meningitidis which causes meningitis

91
Q

what is an example of a gram negative bacilli

A

prevotella intermedia which causes periodontal disease - black pigmented anaerobic rods

92
Q

what is an endotoxin

A

a toxin present inside a bacterial cell wall that is released wehn the bacteria disintegrates

93
Q

where are the lipopolysaccharides

A

the outer membrane of gram negative bacteria

94
Q

what do endotoxin lipopolysaccharides cause

A

fever, inflammation and septic shock

95
Q

which type of bacterial cells are endotoxins found in

A

only gram negative bacteria

96
Q

why are endotoxins found only in gram negative bacteria

A

gram positive bacteria lack an outer membrane so they cannot produce endotoxins

97
Q

what is the key difference between endotoxins and exotoxins

A

endo are released when the cell dies, exo are released while the cell still lives

98
Q

what is an exotoxin

A

a toxin released by a living bacterial cell

99
Q

what is an example of an exotoxin

A

panton valentine leukocydin, which is released from s. aureus

100
Q

what does PVL do

A

causes lysis of the white blood cells neutrophil polymorphonuclear cells. some strains of s. aureus have the enhanced ability to cause PMN lysis after phagocytosis

101
Q

what is the cell wall of gram positive cells like

A

a thick peptidoglycan cell wall containing teichoic acid

102
Q

what is the cell wall of gram negative bacteria like

A

a thin peptidoglycan cell wall with no teichoic acid

103
Q

what is teichoic acid

A

a polymer of ribitol or glycerol phosphate

104
Q

what is a major difference in the cell walls of gram positive cells and gram negative cells

A

gram positive cells do not have an outer membrane and therefore lack the endotoxin lipopolysaccharide

105
Q

what colour do gram positive cells go in a gram stain

A

purple

106
Q

what colour do gram negative cells go in a gram stain

A

red

107
Q

why do gram stains differ depending on gram positive and gram negative bacteria

A

gram positive bacteria have a single thick layer of peptidoglycan above their plasma membrane that can retain the dye.
gram negative bacteria have a thin layer of peptidoglycan sandwhiched between the surface membrane and the plasma membrane so it cannot retain the dye

108
Q

what structural properties do bacteria have that aid them in moving and attaching to other cells

A

pili and fimbriae which are hairlike structures that allow them to attach to the other cells.
flagella are whip like processes that allow them to move

109
Q

what are the functions of the bacterial plasma membrane

A
  • acquire nutrients
  • eliminate waste
  • maintain a constant, organised state
110
Q

what does pleomorphic mean

A

there are multiple layers

111
Q

what are the functions of the cell wall of bacteria

A

protect the bacteria and maintain the shape

112
Q

what are some bacteria also surrounded by

A

a capsule that acts as a shield, and protects the bacteria against phagocytosis, and helps to adhere to surfaces.

113
Q

what are the different shapes of bacteria

A

cocci is round shaped
bacili is rod shaped
spirilla is spiral shaped

114
Q
A

Microbiology (7 decks)

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