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BDS stage 2 > MFD practicals > Flashcards

MFD practicals Flashcards

1
Q

What does the enzyme urease do ?

A

convert urea into ammonia

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2
Q

What happens in the urease test?

A

bacteria mixed with urease

conversion of urea to ammonia

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3
Q

What is the significance of ammonia ?

A

it can raise pH

protect against caries

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4
Q

Which bacterium uses urease ?

A

helicobacter pylori

ammonia made neutralises stomach acid- allow it to survive

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5
Q

What does the enzyme catalase do ?

A

converts hydrogen peroxide into water and oxygen

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6
Q

What does the catalase test involve ?

A

drops of hydrogen peroxide on slide
add loopfuls of bacteria
see fizzing if catalase is present- liberation of oxygen

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7
Q

What happens in the DNase test ?

A

release of free nucleotides by bacteria can turn toludine blue into a pink color

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8
Q

What happens in the coagulase test?

A

latex particles covered in fibrinogen

if bacteria have coagulase- see agglutination of particles turn blue

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9
Q

What is the appearance of staph aureus ?

A

bunches of grapes

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10
Q

Where does staph aureus live ?

A

anterior nares
nasopharynx
skin

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11
Q

What are the properties of staph aureus that enbale it to live on the skin ?

A

can withstand high levels of salt

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12
Q

Is staph aureus commensal or opportunsitic ?

A

both- can cause infections when compromised host

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13
Q

What are some of the diseases that staph aureus can cause ?

A

MRSA
food poisoning
toxic shock syndrome

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14
Q

Is staph aureus gram positive or gram negative ?

A

gram positive

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15
Q

Which enzymes is staph aureus positive for ?

A

coagulase positive
catalase positive
DNase psoitive

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16
Q

What is the advantage of being DNase positive ?

A

allows bacteria to escape extracellular DNA rleeased in infection

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17
Q

What are some diseases oral streptococci can cause ?

A

infective endocarditis

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18
Q

Why can strep salivaris be sold as a probiotic ?

A

makes bacteriocns- AMPs

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19
Q

Which enzymes is strep salivarius positive for ?

A

Urease positive

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20
Q

What is the shape of streo salivarius ?

A

strips of streps

cocci

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21
Q

Is strep salivarius gram positive or gram negative ?

A

gram positive

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22
Q

What type of bacteria is E.coli ?

A

gram negative

enteric

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23
Q

What is e.coli mainly used for ?

A

lab model organism

growth

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24
Q

Which strains of e.coli are pathgoenic ?

A

those that possess the 157th version of the O polysaccharide in the LPS

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25
Q

What can e.coli cause ?

A

UTIs

foodbourne oubreaks

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26
Q

What is the shape of E.coli ?

A

rod shaped bacillus

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27
Q

Which agar is used to grow e.coli and what is its appearance ?

A

grown on macConkey agar

large red colonies

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28
Q

What does e.coli ferment ?

A

lactose

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29
Q

Which enzymes does e.coli possess /

A

catalase positive

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30
Q

What clues can help in species identification ?

A

morphology
colour
smell

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31
Q

What are selective media ?

A

they allow the growth of certian bacteria by inhibitng the growth of others

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32
Q

What are indcator media ?

A

chromogenic tests designed to identify presence of specific bacteria

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33
Q

What do carbohydrate test profiles do ?

A

each row column has a different bacteria and different substrate
phenol red- turns from red to yellow when there is fermentation of sugar to acid.

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34
Q

What are the advantages of broth culture ?

A

large amount of cells cna be cultured

easy to set up

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35
Q

What are the disadvantages of broth culture ?

A

difficult to get a pure colony

difficult to identify different bacteria in the broth

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36
Q

What are the uses of broth culture ?

A

antibiotic susceptibility testing

total viable counts

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37
Q

What does a high temperature do ?

A

above 39

inhibit the growth of most enteric bacteria

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38
Q

What is XLD agar used for ?

A

has phenol red in it
used for identification of enteric bacteria
contains sodium desoxycholate
inihibits gram positive bacteria

39
Q

What is CLED agar used for ?

A

used for culture of bacteria from urine specimens

non-selective

40
Q

What is staph agar used for ?

A

selective for staph aureus
high salt concentration
staphylococci can resist high salt concentrations

41
Q

What are the methods of bacteria identification ?

A

culture
microscopy
molecular technques

42
Q

Which molecular techniques can be used to identify the presence of certain bacteria ?

A

FISH
used to detect specific DNA sequences
PCR can be used to amplify

43
Q

What does LPS consist of ?

A

lipid
core polysaccharide
O polsaccharide- has variants

44
Q

What is significant about the 157th O antigen in E,coli ?

A

it is found in pathogenic e.coli

associated with outbreaks of disease

45
Q

How can we detect specific antigens ?

A

latex agglutination
latex beads are covered in antibody for specific antigen
mix with bacterial suspension
if the bacteria express the antigen there will be agglutination

46
Q

Which factor of S.aureus is responsible for food poisoning ?

A

enterotoxin

47
Q

What substance is used for diagnostic tests of Clostriduum dificile infections ?

A

clostridoum toxins

find in faeces samples

48
Q

Is brilliance candida agar selective or indicative ?

A

both

49
Q

Which gene is most commonly targeted for PCR bacterial identification ?

A

16S rRna gene

50
Q

What is meant by the specifictiy of a diagnostic test ?

A

How many false positives it can detect

51
Q

What changes occur in beta haemolysis on blood agar ?

A

complete lysis of red blood cells

agar turns translucent

52
Q

Which antibiotics are selective for fusobacterium ?

A

vancomycin

neomycin

53
Q

What is FAA ?

A

fastidious anaerobic organism cultivation agar

54
Q

What is reduced transport fluid ?

A

used to provide anaerobic conditions

55
Q

What is MSB agar and what is it selective for ?

A

mits-salivarius agar

bacitracin added make it selective for strep mutans and strep sobrinus

56
Q

Is MSB agar selective or indicative ?

A

both

57
Q

What is TYCS agar ?

A

differnetiate strep mutans from strep sanguis

uses high sucrose content to promote glucan formation vy S mutans

58
Q

Is TYCS selective or indicative ?

A

selective

selects for strep mutans due to high sucrose content whic is utilised to make glucans

59
Q

What is blood agar ?

A

nutrient rich

non selective

60
Q

What is alpha haemolysis ?

A

green colour change
hydrogen peroxide oxidising Haemoglobin
Fe3+ to Fe2+

61
Q

What is beta haemolysis ?

A

complete lysis of RBCs

appears translucent

62
Q

What is gamma haemolysis ?

A

no lysis

63
Q

What does chlorhexidine do and what is it used for ?

A

reduces pahthogenic oral flora and allows the reestablishment of the normal oral flora
used for periodontal treamtent and beofre surgery to reduce bacteriaemia risk

64
Q

What is the equation for CFU/ml ?

A

no of colonies x DF/ vol of culture plate

65
Q

What does the snyder test detect ?

A

acidogenic and aciduric bacteria

supposed caries indicator

66
Q

What are the pH indications of the snyder test ?

A

5.4+ blue
<3.8 yellow
3.8-5.4 Green

67
Q

Which bacteria does the snyder test detect ?

A

lactobacillus
an acidophile
found in caries lesions- the carious lesions select for them

68
Q

Why is there a colour change to yellow in the snyder test ?

A

lactic, acetic and formic acid

69
Q

Why does P.gingivalis produce dark pigments ?

A

prophyryn pigments contain haem from the host

70
Q

Why was there a lot of alpha haemolysis in the kiss plate ?

A

oral streptococci are alpha haemolytic

71
Q

How can we work out CFU/ml ?

A

DF x number of colonies/ volume of culture plate

72
Q

Which carbohydrate is fermented in the snyder test ?

A

glucose

73
Q

Which acids are produced in the snyder test?

A

lactic acid
formic acid
acetic acid

74
Q

What is the main function of fructans in plaque ?

A

energy

75
Q

What type of spectrum antibiotic is methicillin ?

A

broad spectrum

76
Q

How did MRSA acquire resistance ?

A

through pencillin binding protein

mecA gene

77
Q

How are gram negative bacteria intrisically resistant to vancomycin ?

A

LPS

78
Q

How does vancomycin have to be administered and why ?

A

IV

too big- highly glycosylated glycopeptide- too big too pass across membranes

79
Q

What is amoxicillin ?

A

moderate spectrum antibiotic
against gram psitive bacteria
and limited gram negative bacteria

80
Q

What is metronidazole ?

A

active agaisnt gram positive and gram negative

81
Q

What is clavulanic acid ?

A

inhibits beta lactamases

combine with amoxicillin to make augementin

82
Q

How do we carry out antibiotic sensitivty testing ?

A

carry out broth dilution
make serial dilutions of antibiotic
innocualte with bacteira
innocualte overnight

83
Q

Is MBC or MIC usually bigger ?

A

MBC

84
Q

What are MIC ad MBC useful for ?

A

drug efficacy
admistration
resistance

85
Q

What does the ZOI indicate in antibiotic testing ?

A

sensitivity of bacteria to the antibiotic

larger the ZOI- more potent antibiotic

86
Q

What does it mean if bacteria are present in the ZOI ?

A

they are resistant

87
Q

What does PBP 2a do ?

A

confers resistance as it allow transpeptidase to work in the presence of methicillin

88
Q

What makes staph aureus appear yellow on agar ?

A

makes a pigment called staphloxanthin

89
Q

What is the function of staphyloxanthin ?

A

protects cells against oxidative stress

90
Q

Which test can distinguish between staph aureus/ epidermidis ?

A

coagulase test- positive fro staph aureus

91
Q

In what form does fluoride enter bacterial cells ?

A

HF- uncharged so cn corss membranes

92
Q

how does vancomycin work ?

A

binds to peptidoglycan and interferes woth synthesis

93
Q

Why is vancomycin inappropriate for e,coli infections ?

A

e.coli is gram negative

vancomycin cant get past the LPS

BDS stage 2 (28 decks)

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