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BDS stage 2 > Microbiology for dentists theme 1 > Flashcards

Microbiology for dentists theme 1 Flashcards

1
Q

What are examples of microorgansims ?

A 
bacteria
viruses
archaea
fungi
protozoa
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2
Q

What are the origins of life ?

A

4 bn years ago cellular life came into being
2 bn years ago modern eukaryotes existed
0.5 bn years ago multicellular life evolved

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3
Q

What is evolution ?

A

the process of change over time which results in new species

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4
Q

What is phylogeny ?

A

evolutionary relationships between organisms

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5
Q

How is phylogeny determined ?

A

genetic relationhips- looking at the rRNA gene

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6
Q

Why is the rRNA gene used ?

A

present in all organisns

shows a high degree of variability

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7
Q

What is the process for determining phylogeny ?

A

isolate DNA
Make copies of the rRNA gene
sequence the DNA
analyse and compare

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8
Q

Which microorganisms dominate the tree of life ?

A

bacteria
arachaea
eukarya

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9
Q

What are example of eukarya ?

A

protozoa
animals
fungi
plants

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10
Q

What are archaea ?

A

they diverged from bacteria
they have some similarities to eukarya - similar DNA replication
correlation with periodontal disease

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11
Q

What are protozoa ?

A

single celled eukaryotes
found in aquatic environments- dental unit waterlines
graze on bacteria

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12
Q

What is an example of protozoa ?

A

plasmodium- malaria

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13
Q

What are fungi ?

A

simple eukaryotes
make multicellular structures
grow as branched tubes

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14
Q

What is the fungi cell wall made of ?

A

chitin

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15
Q

What are viruses ?

A

obligate intracellular parasites
acellular
nucleic acid in a protein coat
evovle rapidly

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16
Q

What are prions ?

A

proteinaceous infectious agents
proteins that have changed conformation from an alpha helix to a beta pleated sheet
they are autocatalytic- can cause further conformational changes
leads to degeneration in brain function
extremely resistant to heat

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17
Q

How can prions be transmitted ?

A

contamianted food
hormone treatments
surgical instruments

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18
Q

How is a prion formed ?

A

normal protein adopts a misfolded protein shape
prion binds to normal proteins
leads to the conversion of more protesins

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19
Q

What do prions aggregate to form ?

A

amyloid fibrils

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20
Q

How are amyloid fibrils made ?

A

from the stacking of beta pleated sheets

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21
Q

What do amyloid fibrils do ?

A

disrupt cell function

cause neuro-degenerative disorders

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22
Q

What type of neuro-degenerative disorders do prions cause ?

A

transmissable spongiform encephalopathies

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23
Q

What are prions resistant to ?

A

heat resistant

protease resistant

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24
Q

What are the 3 categories of prion disease ?

A

spontaneous
acquired
inherited

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25
Q

What is an example of a spontaneous prion disease ?

A

sporadic CJD

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26
Q

What is an example of inherited prion disease ?

A

familial CJD

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27
Q

What is an example of acquired prion disease ?

A

Kuru

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28
Q

Why do prions have long incubation periods ?

A

they replicate slowly

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29
Q

What property of prions allows them to form plaques ?

A

theyre insoluble

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30
Q

How is neuronal tissue death via prions visible ?

A

spongiform pathology

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31
Q

What is the relevance of prions to dentistry ?

A

dental tissues are considered low risk
could be iatrogenic transmission
difficult to destroy- essential to autoclave instruments and use single-use instruments

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32
Q

What is a major problem with prions ?

A

they cant be detected as they have no assay

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33
Q

What is the basic structure of a virus ?

A

a nucleic acid and a protein capsid coat

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34
Q

What are the 2 types of proteins ?

A

enveloped and non-enveloped

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35
Q

What are enveloped viruses ?

A

they consist of the nucleic acid and the protein capsid and the lipid layer which is embedded with glycoproteins

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36
Q

What are the 3 types of viral genome shapes ?

A

linear
circular
segmented

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37
Q

What are the 2 types of nucleic acid ?

A

DNA and RNA

single stranded or double stranded

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38
Q

What is the purpose of the viral genome ?

A

to encode for proteins- structural, proteases and enzymes

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39
Q

Which enzymes do viruses need ?

A

reverse transcriptase
DNA polymerase
RNA polymerase

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40
Q

What is the mode of action for a virus ?

A
  1. genome codes for proagation proteins
  2. Infection of the host
  3. Genome replication
  4. Invasion of immune system
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41
Q

Which types of virues are most likely to cause disease ?

A

Single stranded RNA

Double stranded DNA

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42
Q

What is the life cycle of a DNA virus ?

A 
phagocyte brings virus 
virus infects epithelial cell
harnesses replication machinery 
trasncribe into RNA 
RNA is translated into viral proteins 
lysis - pathology
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43
Q

What is the life cycle of an RNA virus ?

A

viruses contain reverse transcriptase- convert viral RNA into DNA
Replicate DNA
Integration into the genome
transcribed and translated
more RT Made, capsid proteins and envelope proteins to assemble new viruses

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44
Q

What is persistence ?

A

some proviruses will insert into the viral chromosome and remain there- evade the immune system - latent

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45
Q

What is an example of an RNA enveloped virus ?

A

HIV

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46
Q

What is an example of an RNA non-enveloped virus ?

A

Rhino

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47
Q

What is an example of a DNA enveloped virus ?

A

Herpes

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48
Q

What is an example of a DNA non-enveloped virus ?

A

HPV

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49
Q

What are some viruses that are systematic but cna have oral effects ?

A

MMR

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50
Q

What are the oral signs of measles ?

A

rash-kopliks spots

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51
Q

What are the oral signs of mumps ?

A

salivary gland inflammation

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52
Q

What are the oral signs of rubella ?

A

Rash

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53
Q

What are some viral infections of the mouth ?

A

hand, foot and mouth disease
Herpes
HIV

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54
Q

What is hand, foot and mouth disease ?

A

enterovirus that causes oral blisters

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55
Q

What is Herpes ?

A

Large class of structurally similar viruses

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56
Q

What is HPV ?

A

linked to oral cancer

causes papillomas of the oral mucosa and the genitals

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57
Q

Which HPV are associated with HPV ?

A

16 and 18

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58
Q

Which HPV are restricted to the oral cavity ?

A

13 and 32

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59
Q

What does HIV cause ?

A

AIDS

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60
Q

What is HIV Associated with ?

A

oral candidosis

NUG

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61
Q

Which cells does HSV 1 infect ?

A

mucosal epithelial cells

neuronal cells

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62
Q

How is HSV 1 latent ?

A

hides in the immune system until reactivated

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63
Q

What does reactivated HSV1 cause ?

A

stomatitis

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64
Q

How is HSV1 transmitted ?

A

through saliva

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65
Q

What are the factors that lead to NUG ?

A

stress
smoking
HPV

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66
Q

What plaque control methods are used for NUG ?

A

ultrasonic
chlorohexidine
metronidiazole
OHI

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67
Q

What are the symptoms of HSV1 ?

A

cold sores

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68
Q

What are the symptoms of Varicella-zoster ?

A

child- chicken pox

adult-shingles

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69
Q

What are the symptoms of epstein barr ?

A

Glandular fever

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70
Q

What are the symptoms of cytomegalovirus ?

A

congential defects

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71
Q

What are the symptoms of HHV8?

A

Kaposis sarcoma-affects AIDS patients

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72
Q

How is varicella - zoster virus trasnmitted ?

A

aerosols and direct contact

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73
Q

How do shingles appear ?

A

in the facial nerve tract

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74
Q

Why arent kids vaccinated against chicken pox ?

A

because its mild

also vaccinating kids reduced the boosting of immunity ex-chicken pox adults get from being exposed to chicken pox kids

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75
Q

How is Hepatitis B transmitted ?

A

blood saliva STI

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76
Q

What are the severe effects of Hepatitis B ?

A

hepatocellular carcinoma

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77
Q

Is Hep B present in the mouth ?

A

it is present in the mouth but does not cause oral disease

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78
Q

How can you look for viral infection ?

A

clinical apperance
lab tests- ELISA and sero conversion to look for antibodies
viral culture
histology from a biopsy

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79
Q

How can we prevent viral infections ?

A

cross infection control

vaccines

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80
Q

Which drugs are used in anti-viral healthcare ?

A

acyclovis

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81
Q

What are the characteristics of prokaryotes ?

A

no membrane bound organelles
haploid
no fusion of gametes

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82
Q

Why are fungi described as chemoorganotrophs ?

A

secrete extracellular enzymes which digest organic material

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83
Q

What are hyphae ?

A

network of filaments of fungi

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84
Q

What are mycelium ?

A

they grow over surfaces in a network

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85
Q

What is the fungi cell wall made of ?

A

chitin

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86
Q

What is different about fungi cell membranes ?

A

they contain ergestrol rather than cholesterol

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87
Q

What colour is the gram stain in GP bacteria and why ?

A

Purple

thick peptidoglycan layer able to retain the crystal-iodide complex

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88
Q

What are flagella ?

A

rotating protein motors that allow motility

made of flagellin sub units

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89
Q

What is rotation in flagella couple to ?

A

flow of protons across the membrane

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90
Q

What is the method for the gram stain ?

A 
create a heat fixed smear
flood with crystal violet 
add iodide complex 
decolourise with alcohol
counterstain with safarnin
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91
Q

What are acid-fast bacterial cell walls ?

A

very high lipid/wax content
contain mycolic acids
found in mycobacterium TB

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92
Q

What is the method for detecting acid fast bacterial cell walls ?

A

detected with carbol fuschin
driven in with heat
destain with 3% alcohol

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93
Q

What are the cytoplasmic membranes of gram positive and gram negative cell walls ?

A

phospholipid bilayer

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94
Q

What is the structure of gram negative outer membranes ?

A

LPS

asymmetrical

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95
Q

What are fimbriae ?

A

protein filamentous structures
enable cells to adhere to surfaces
aid in biofilm production

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96
Q

What are pili ?

A

used in conjugation- DNA transfer
used in adhesion
found in streptococus pyogenes
type 4 have a twitching motility

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97
Q

What are capsules made of ?

A

polysaccharides and the proteins

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98
Q

What is the purpose of the capsule ?

A

aid adherence - biofilm production
evade phagocytosis
stop desiccation (protect against drying out )

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99
Q

What are cell inclusions ?

A

packets of energy resources

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100
Q

What is the purpose of cell inclusions ?

A

safe way to store energy and avoid osmotic stress

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101
Q

What are some examples of cell inclusions ?

A

glycogen

poly-B-hydroxybutyric acid

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102
Q

What are endospores ?

A

certain bacteria can only form them

highly differentiated cells that are very resistant

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103
Q

How are endospores destroyed ?

A

by autoclaving

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104
Q

What is an examples of endospores ?

A

clostridium dificil

arent killed by antibiotics

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105
Q

What do bacteria require to grow ?

A

they consume and produce energy-
they require macronutrients and micronutrients
water
trace elements

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106
Q

What are heterotrophs ?

A

obtain carbon from organic material

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107
Q

What are autotrophs ?

A

obtain carbon from C02

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108
Q

What are auxotrophs ?

A

cant synthesis organic compounds like amino acids

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109
Q

What is fermentation ?

A

an anaerobic process

organic compound used as the electron acceptor and donor

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110
Q

What is respiration ?

A

aerobic process

electron donor is oxidised with oxygen

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111
Q

Where do fermentation and respiration happen ?

A

in both humans and bacteria

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112
Q

What is homolactic fermentation ?

A

fermentation of hexose sugars leads to 2 lactate and 2 H+

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113
Q

What is the relevance of lactic acid ?

A

major product found in dental caries

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114
Q

Which bacteria in plaque ferment to produce lactic acid ?

A

streptococus mutans

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115
Q

What is the first step in both respiration and fermentation ?

A

glycolysis

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116
Q

How is ATP produced in fermentation ?

A

substrate level phosphorylation

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117
Q

How is ATP produced in respiration ?

A

oxidative phosphorylation

electron transport chain

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118
Q

How much ATP is made in aerobic respiration ?

A

38 ATP

included glycolysis and the citric acid cycle

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119
Q

What is the purpose of the citric acid cycle ?

A

to produce reducing agents

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120
Q

What protein is needed for ATP synthesis in respiration ?

A

FOFI ATPase

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121
Q

What is FOFI ATPase ?

A

A highly abundant proten growing in bacterial cell walls

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122
Q

How does FOFI ATPase generate ATP ?

A

flow of protons into cells

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123
Q

How do Oral bacteria use FOFI ATPase ?

A

streptococus mutans uses ATPase to pump protons out of cells when conditions are too acidic to reduce the acidity

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124
Q

What is the definition of bacterial growth ?

A

irreversible increase in biomass and usually numbers of bacteria

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125
Q

How can we measure bacterial growth ?

A

microscopy
colony forming units
absorbance
growth curves

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126
Q

What is the process of bacterial cell division ?

A 
binary fission 
DNA replication
cell elongation 
septum formation 
distinct cells 
cell separation 
distinct cells
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127
Q

How is bacterial growth described ?

A

exponential

number of cells doubles during a constant time

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128
Q

What is the risk of such a high increase in a short time ?

A

increases the risk of pathogenic bacteria

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129
Q

What are the phases of bacterial growth ?

A

exponential
ststionary
death

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130
Q

What are the 3 methods used for measuring bacterial growth ?

A

microscopic counts
viable and serial dilutions
tubidimetric methods

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131
Q

Why is e.coli used as a lab model organism ?

A

more is known about it than any organism
grows rapidly and has simple nutritional requirements
established genetics and genome

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132
Q

What is the e.coli genome like ?

A

circular chromosome made of 4.6 million base pairs

encodes around 4400 base pairs

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133
Q

What is an operon ?

A

genes encoding enzymes in a single biochemical pathway

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134
Q

What are plasmids ?

A

small circular pieces of DNA found in varying numbers in the cell

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135
Q

What types of genes do chromosomes carry ?

A

genes that are useful but arent essential for survival

eg. antibiotic resistance

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136
Q

How can genetic information be exchanged by plasmids ?

A

bacteria die and release plasmids that can be absorbed by bacteria

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137
Q

What are the 3 types of horizontal gene transfer ?

A

conjugation
transformation
transduction

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138
Q

What does horizontal gene transfer have the ability to do ?

A

ability to change the genotype and the phenotype of an organism
make the bacteria “fitter”- multiply faster or give resistance

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139
Q

What is DNA transformation ?

A

DNA uptake freely from the environment

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140
Q

What is transduction ?

A

bacteriophage mediated
bacteriophage will infect a bacterial cell and take up the host DNA
it will then inject the DNA into another cell and then integrate it into the chromosome - donor DNA will take up new functions

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141
Q

What is conjugation ?

A

pilus mediated
pilus extends from the donor to the recipient and adheres
plasmids are transported down the pillus

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142
Q

How is DNA incorporated into the chromosome of the recipient ?

A

Homologous recombination

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143
Q

Give an example of transformation using tryptophan ?

A

e.coli strains that lacka a tryptophan pathway grow on an a tryptophan lacking agar- no growth
take DNA from tryptophan from tryptophan positive cells - cells will uptake DNA
grow on tryptophan agar- see visible growth

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144
Q

What are the goals of genetic manipulation ?

A

knock out genes
change individual amino acids in a protein
FISH
produce recombinant proteins like insulin

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145
Q

What are the steps in Recombinant DNA technology ?

A

Creation of the recombinant DNA
Cloning of the DNA in an organism
Using the DNA - express the gene

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146
Q

How can we clone recombinant DNA ?

A

amplify the DNA by introducing it into a living cell which will produce many identical copies

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147
Q

What are the tools for Recombinant DNA technology and why ?

A

enzymes- to cut DNA and RNA
vectors - act as a vehicle to transport the DNA into host cell for replication
cells- Amplify and express the DNA
DNA and RNA - Raw genetic material

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148
Q

Which enzymes are needed in recombinant DNA technology ?

A

Restriction enzymes
SNA Ligase
Taq polymerase
Reverse transcriptase

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149
Q

What do restriction enzymes do and give an example ?

A

cleave and cut DNA at very specific sequences- molecular scissors
eg. Restriction endonuclease

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150
Q

What does DNA ligase do ?

A

stick DNA fragments together

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151
Q

What does Taq polymerase do ?

A

used in PCR- creates multiple copies of the DNA fragment

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152
Q

What does reverse transcriptase do ?

A

convert RNA into DNA

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153
Q

How are restriction enzymes produced and whyn ?

A

naturally produced by bacteria to cleave bacteriophage DNA

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154
Q

Which sequences do restriction enzymes recognise and what do they produce ?

A

recognise 4-8 base pairs in a palindromic sequence

produce either sticky or blunt ends

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155
Q

What are sticky ends ?

A

they are overhanging at either the 5’ or 3’ end

compatible overhangings are annealed with DNA ligase

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156
Q

What do vectorrs contain that allows the insertion of the new recombinant DNA ?

A

restriction sites so DNA can be efficiently introduced into host DNA

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157
Q

How can we check which cells have taken up the DNA ?

A

the plasmid will have an antibiotic resistance gene - if the cell has taken up the plasmid the gene will be expressed and the cells will be able to be grown on agar containing penicillin

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158
Q

What do vectors contain to allow for expression of the inserted gene ?

A

regulatory sequences

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159
Q

How do plasmids replicate ?

A

independent of the bacterial chromosome

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160
Q

What do plasmids have that allows recognition by the host replication machinery ?

A

origin of repication

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161
Q

What is the polylinker ?

A

a piece of synthetic DNA that allows the insertion of new gene

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162
Q

What does the polylinker contain ?

A

lacZ gene which codes for the B-galactosidase enzyme
which turns a dye from blue to white
If the polylinker is disrupted - gene is successfully added- blue colonies

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163
Q

What are other example of vectors beside plasmids ?

A

phagemids
cosmids
bacteriophages

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164
Q

What are cosmids and phagemids ?

A

genetically engineered hybrids which replicate as a plasmid but can be packaged as a bacteriophage

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165
Q

How is the recombinant plasmid inserted into the cells ?

A

via transformation- either by electroporation or using Calcium chloride heat shock, 42 degrees for 3 mins

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166
Q

Where does each cell in a colony arise from ?

A

a single e.coli cell

each cell in the colony will contain copies of the same plasmid - clones

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167
Q

What were the disadvantages of using amimal insulin ?

A

side effects
difficult to purify
autoimmune reactions

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168
Q

How is recombinant insulin made ?

A

the gene for proinsulin has 2 introns - DNA is first converted to mRNA
then reverse transcribed into DNA to get rid of introns
the gene is inserted into a plasmid
plasmid inserted into cell and cloned in E.coli

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169
Q

Examples of other proteins made using recombinant technology ?

A

Erythropoietin

Tpa

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170
Q

How can recombinant DNA be applied dentally ?

A

recombinant DNA can be used to manipulate genes

create a genetically altered strain of S.mutans that doesnt produce lactic acid

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171
Q

What is a planktonic solution ?

A

a solution of cells that are homogenous , single species and nutrient rich

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172
Q

What is a surface associated collection ?

A

they have limited hetrogeneity
single species
nutrient rich

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173
Q

What are natural collections of bacteria ?

A

in the from of a structured community with organic matter and active microbes
heterogenous
mixed species
nutrient limited (gradient of nutrients)

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174
Q

What is a biofilm ?

A

a functioning and growing community of microbial cells encased within a matrix polymers and associated with a surface

175
Q

In nature how are most bacteria found ?

A

associated at a surface

176
Q

How are biofilms produced ?

A

attachment of planktonic cells

sticky matrix develops

177
Q

What is the difference in growth rates between biofilms and planktonic solutions ?

A

biofilms have mixed growth rates

planktonic cells have uniform growth rates

178
Q

What is the difference in the distribution of oxygen and nutrients between planktonic cells and biofilms ?

A

even distribution of nutrients and oxygen in planktonuc solutions
uneven distribution in biofilms

179
Q

What is the contact between cells like in biofilms and planktonic solutions ?

A

biofilms- cells in close contact

planktonic- cells separated

180
Q

Is there an ECM in biofilms ?

A

yes

not in planktonic solutions

181
Q

What are emergent properties ?

A

properties that emerge as a result of putting things together
bacteria behave differently in cultures and biofilms

182
Q

What is the difference in antibiotic resistance between a biofilm and a solution of cells ?

A

biofilm is 1000 x more resistant to antibiotics than planktonic cells

183
Q

Are biofilms likely to be more or less pathogenic than planktonic cells ?

A

more pathogenic

184
Q

What can biofilms do with the immune system ?

A

biofilms can hide from host immunity

185
Q

What type of niches can biofilms produce ?

A

strictly anaerobic bacteria can be found at interfaces if the bacteria surrounding them suck oxygen away

186
Q

Where are biofilms found ?

A

anywhere there is an interface
moisture
nutrients and energy source

187
Q

What is the biofilm structure ?

A

3D
Open
water channels permeate the matrix
heterogeneous distribution with microcolonies found
unequal distribution of waste and nutrients as the marix impedes mass transfer
oxygen and nutrient gradients

188
Q

What is the matrix a mixture of ?

A

polysaccharides
proteins
nucleic acids

189
Q

What is the purpose of the matrix ?

A

bind cells together
trap nutrients for microbial growth
prevent cell detachment

190
Q

Which smaller molecules may also be trapped in the matrix ?

A

nutrients
metals
signalling molecules

191
Q

What is pseudomonas aeruginosa ?

A

model bacterium used for biofilm development
makes mushroom shaped biofilms
opportunistic pathogen
present in water and lungs of those with CF
catheter infections

192
Q

What are diagnostic criteria for biofilm infections ?

A

pathogenic
associated with a surface
aggregated cells in clusters with a matric
resistant to antibiotics

193
Q

Why are bacteria resistant to antibiotics ?

A 
poor penetration 
slow growing 
persister cells 
sequestration from the immune system 
elevated expression of efflux pumps
194
Q

How does slow growing cells lead to antibiotic resistance ?

A

antibiotics work by virtue or targeting fast bacterial growth processes such as cell wall synthesis .
Biofilm bacteria are slow growing - no processes to target

195
Q

Is growth a major factor to consider when determining antibiotic resistance ?

A

no growth is a minor factor because evidence has showed that antibiotics are just as effective at targeting mRNA synthesis in planktonic and biofilm bacteria

196
Q

What are persister cells ?

A

populations of bacteria contain a small proportion of inactive dormant cells
difficult to kill dormant cells with antibiotics
they are significant proportion of biofilm bacteria
responsible for hip joint replacements 15-20 years later

197
Q

How do biofilm bacteria evade the immune system ?

A

resitant to phagocytosis- inflammatory cells cant penetrate matrix
antibodies penetrate poorly
adaptive responses

198
Q

How does pseudomonar Spp evade the immune system ?

A

produces rhamndlipids which kill neutrophils

interactions with oral stretococci produces a complement evading protein

199
Q

Which bacteria upregulate efflux pumps ?

A

e.coli
Pseudomans aeurigonosa
candida albacans
efflux pumps are not effective against all antibiotics

200
Q

What is mass transfer ?

A

movement in and out

201
Q

How can we measure mass transfer ?

A

using fluorescently labelled latex beads

202
Q

Is diffusion impeded by the matrix ?

A

it can be but not for small molecules
water molecules can be carried through water channels
large molecules are also only weakly limited

203
Q

Is the matrix charged ?

A

yes the matrix is anionic

204
Q

What is the significance of the matrix being charged ?

A

metal cations can become trapped in an anionic matrix

reactive molecules such as peroxide can be ianctivated by the matrix

205
Q

What is the structure of the matrix ?

A

it is thought to be a 3D web.

206
Q

What is the pan genome ?

A

all gene present in a whole species

207
Q

What is the size of the genome of Haemophilus Influenzae ?

A

1.8 million base pairs

208
Q

What is the smallest naturally occuring genome ?

A

Cassoerella mdii

209
Q

What is the largest bacterial genome ?

A

Soragrium Cellulosom

210
Q

When was the first human genome draft published ?

A

2001

211
Q

How are microbial genomes represented ?

A

open reading frames on the outside

genes colour coded by function

212
Q

What does an ORF consist of ?

A

ribosomal binding site
starting codon
coding sequence

213
Q

How do computers determine if ORFs are genuine ?

A

find possible start/stop codons
count codons between to see if it could be a protein- need 300 amino acids
find a possible ribosome binding site

214
Q

What is the core genome ?

A

shared by all strains of the same species

for basic functions like DNA Replication

215
Q

What is the pan genome ?

A

includes optional extras-present in some strains of the species but not all eg.genes for virulence
pan=core+accessory

216
Q

What are chromosomal islands ?

A

regions of the bacterial chromosome that are foreign origin
contain clustered genes for extra properties
found by comparison of the core and pan genome

217
Q

What are pathogenicity islands ?

A

chromosomal islands that encode genes for virulence factors

218
Q

Why are chromosomal islands assumed to be foreign ?

A

come about via horizontal gene transfer
come about via transposition
codon bias that differs from the norm
found in some strains but not others

219
Q

What is the mircobiome ?

A

total complement of microorganims in an environment (including those associated with a higher organism)

220
Q

What does metagenomic sequencing do ?

A

obtains information about all DNA present

221
Q

Which gene can be specfically sequenced ?

A

16S rRNA gene

222
Q

Which organisms do not have the 16S rRNA gene ?

A

viruses- lack rRNA gene

fungi-18s rRNA gene

223
Q

What technique should you use to identify which microbes are present ?

A

SSU rRNA approaches

224
Q

Which techniques should you use to observe microbial activity ?

A

look at
RNA- metatranscriptomics
Proteins- Metaproteomics
Metabolites- Metabonomics

225
Q

What techniques should you use to assess the genetic potential of a microorganism ?

A

Metagenomics

226
Q

What is beta diversity ?

A

diversity between individuals at a single body site

227
Q

What is alpha diversity ?

A

Diversity between individuals at different body sites

228
Q

Which is generally lower beta or alpha diversity ?

A

beta diversity

229
Q

What can the core microbiome influence ?

A 
lifestyle 
genotype 
physiology 
immune system 
pathobiology
230
Q

What does mothers milk contain ?

A

antibodies that lead to protection against pathogens and sugars that good bacteria feed on

231
Q

What diseases does the human microbiome have a role in determining ?

A

obesity
IBD
liver development
DM

232
Q

What is the link between mouthwashes and blood pressure ?

A

normally oral bacteria convert nitrates to nitrites
in saliva that we swallow
reduced to nitric oxide
widens blood vessels
mouthwashes get rid of the bacteria that do this- leads to increase in BP

233
Q

What is disease aetiology ?

A

study of the causation of diseases

234
Q

What is the germ theory of disease ?

A

states that microorganisms lead to disease

235
Q

What is anthrax ?

A

a disease of cattle and sometimes humans

caused by bacillus anthracis

236
Q

What did koch establish regarding anthrax ?

A

bacteria were always present in blood of animal with disease
took samples and cultured in virtreous humour
injected blood into mouse
injected into mouse- got anthrax

237
Q

What is bacillus anthracis ?

A

endospore forming
gram positive soil bacterium
3 forms

238
Q

What are the criteria that form Kochs Postulates ?

A
  1. Organism must be present in all cases of disease and not in healthy individuals
  2. Must be able to be isolated in pure culture
  3. Isolated cells must cause disease in a suitable animal
  4. the organism must be reisolated from the infected animal
239
Q

Where are Legionnaires bacteria found ?

A

in the environment - usually warm water environments

240
Q

How do legionella bacteria grow ?

A

grow with amoebae - allows them to survive in harsh environments.

241
Q

From 2011 what must all dental practices have ?

A

a legionnaires risk assessment

242
Q

Under what circumstances is it not possible to fulfil Kochs postulates ?

A

Asymptomatic carriers- carry organism and not have disease
viruses- could not be cultured in 1900s as well as prions
some infections are polymicrobial
might not be suitable animal organisms
might be the level of the bacterium rather than its presence that leads to disease

243
Q

How do organisms cause disease ? 6 Is

A 
implantation 
in-utero 
ingestion 
inhalation 
injection 
inunction (rubbing)
244
Q

What is the advantage of using DNA analysis to identify infectious agents ?

A

circumvents the isolation of the infectious agents
very sensitive
quantitative

245
Q

What does commensal mean ?

A

an organism that lives in harmless association with its host ?

246
Q

What is colonisation ?

A

sustained presence of an organism at a body site

247
Q

What is a pathogen ?

A

an organism that can cause disease in otherwise healthy individuals

248
Q

What is a carriage ?

A

When the host acts as a source of infection but shows no symptoms themselves

249
Q

What is an opportunistic pathogen ?

A

an organism which requires the host to have a pre-existing deficit before it causes disease

250
Q

What is an infection ?

A

growth of a non native microorganism at a body site without damage to the host

251
Q

What is virulence ?

A

a measure of the capacity of microorganism to cause disease

252
Q

What are virulence factors ?

A

genes which express proteins or other molecules which contribute to virulence

253
Q

What are endogenous infections ?

A

caused by infectious agents that are already present in the body but have dormant and inactive for some time.

254
Q

What are exogenous infections ?

A

acquired from sources outside the patient

255
Q

What are examples of virulence factors that pathogens can possess ?

A

adhesins
invasins
toxins
extracellular enzymes

256
Q

What do virulence factors enable pathogens to do ?

A

survive and replicate in the host

257
Q

What does bordotella pertussis cause ?

A

whooping cough

258
Q

What does yeninia pestis cause ?

A

plague

259
Q

What are some examples of opportunistic pathogens ?

A

staphyloccus epidermis - catheters develops biofilms
Pseudomonas aeuriginosa- burns can break down skin allowing the bacteria to penetrate.
E.coli

260
Q

What are the stages of an infection ?

A 
exposure to pathogens 
adherence to skin and mucosa 
invasion through epithelium 
infection 
growth and production of virulence factors 
toxicity and invasiveness
261
Q

What is adherence ?

A

initial attachment and interaction between bacterial surface and tissue

262
Q

Which bacterial structures allow adherence ?

A

pilli
fimbriae
surface proteins

263
Q

What does E.coli do with its pili ?

A

it has type 1 pilli that adhere to epithelial cells in the urinary tract and stop the bacteria from being flushed out

264
Q

What does vibrio cholerae do ?

A

it is highly motile in bodily fluids and mucosa of intestinal epihelium
make contact with cells and causes disease

265
Q

How does the skin act as defence ?

A

natural barrier

antimicrobial fatty acids and antibacterial peptides

266
Q

How does the stomach act as a defence ?

A

it has a very high acidity of around 2
lots of bacteria needed to vause infection however in the case of proton pump inhibitor medicine a lower number of bacteria are needed to infect

267
Q

What do tears contain ?

A

lysozymes that degrade bacterial cell walls

268
Q

What do epithelial cells have that can protect against infection ?

A

tight junctions - inhibit pathogen invasion and infection

269
Q

What are the bodys adaptive host defences ?

A

phagocytosis
inflammation
antibodies

270
Q

How can bacteria overcome skin defences ?

A

they have keratinases that degrade the junctions between epithelial cells and penetrate skin

271
Q

How do bacteria overcome flushing ?

A

flagella and fimbriae carry out adherence - attach to mucosa to stop flushing out

272
Q

How can bacteria overcome mucus ?

A

they can swim and degrade mucin

273
Q

How can bacteria evade phagocytosis ?

A

they have VI capsules that prevent against complement fixation

274
Q

How can bacteria overcome antibodies ?

A

have proteases that break down antibodies
kill host defence host cells
antigenic variation

275
Q

What is antigenic variation ?

A

infectious agents able to change their surface proteins and carbohydrates expressed leading to evasion from the immune system
this leads to a cycling of fever

276
Q

What is bacteraemia ?

A

invasion of bacteria into the blood stream

277
Q

What is septicaemia ?

A

infection in the blood stream

278
Q

How can septicaemia be detected ?

A

cytokine storm- increased levels of cytokines

279
Q

What are the ways in which bacteria can invade ?

A 
lungs
gut 
UT
nerve pathways
cell to cell
280
Q

What are examples of tissue degrading enzymes and what do they do ?

A

collagenase- breaks down collagen
hyaluronidase - breaks down junctions between cell walls
haemolysin- lyses erythrocytes

281
Q

What do siderophores do ?

A

take up iron

282
Q

What are some exmaples of microbial virulence factors ?

A

O-antigen inhibits phagocyte killing

VI capsule stops complement binding

283
Q

What is an example of an endotoxin ?

A

LPS in gram negative outer membrane

causes fever, septic shock and inflammation

284
Q

What are exotoxins ?

A

they are secreted by bacteria

285
Q

What is the problem with exotoxins ?

A

the dont require the bacterium to cause infection

antibiotics are now useless so better to vaccinate against

286
Q

What are some examples of exotoxins ?

A

tetanus toxin

diptheria toxin

287
Q

Where can you find tetanus toxin ?

A

soil - it attacks the CNS

288
Q

What does the diptheria toxin do ?

A

stops cell protein synthesis

289
Q

What is clostridium tetani ?

A

gram postive, spore forming rod
secretes a neurotoxin that stops neurotransmitter release from inhibitory synapses
leads to lockjaw

290
Q

What is clostridium botulinim ?

A

bacterium found in soil, water and food

tinned food undergoes botulinum cook

291
Q

What is the clostridium botulinum toxin used for ?

A

treat muscle conditions

botox

292
Q

What does diptheria do ?

A

inhibits protein synthesis

causes a pseudomembrane that can block the airways

293
Q

What is necrotising fascitis ?

A

tissue destruction by toxins initiate an overactive immune response
flesh eating

294
Q

What are some pathogens involved in necrotising fascitis ?

A

S.pyogenes and MRSA

295
Q

What is an acute infection ?

A

short duration

296
Q

What is a chronic infection ?

A

long duration

297
Q

What are some factors that increase susceptibility to disease ?

A

trauma
age
nutrition
hormones

298
Q

How has their been a shift in the way that we now view the way disease is caused ?

A

Kochs gave us the idea that the presence of a pathogen was enough to cause disease but now we think it might be the level rather than the presence that can cause disease.

299
Q

What is dysbiosis ?

A

a shift in the balance of bacteria towards an unhealthy number of bacteria

300
Q

Sequencing the 16srRNA gene tells us what ?

A

it can help us identify the pathogen but it is not exact- OTU- operational taxonomic unit

301
Q

What do we need to be careful about when we find pathogens in disease ?

A

correlation is not causation

302
Q

What is metagenomic sequencing ?

A

sequencing all the DNA present including non bacterial and then suing bioinformatics to predict function of DNA

303
Q

Identifying bacteria from different body sites led to what conclusion ?

A

different body sites are dominated with certain bacteria

core taxa at every site

304
Q

What is the commensal gut microbiota essential for ?

A

the development of an immune system

305
Q

Which diseases are associated with differences in the gut microbiota ?

A

Obesity
Colorectal cancer
IBD

306
Q

What can antibiotics potentially do ?

A

control pathogens but also lead to dysbiosis

307
Q

What is important about microbial function when it comes to disease ?

A

disease isnt just about the pathogens being present- changes in the function of the community can also be a driver for disease.
eg. Crohns disease- reduced expression of amino acid metabolism

308
Q

What is associated with inflammatory bowel disease ?

A

genetics
change in the microbial microbiotia - composition and function - decrease in amino acid synthesis
decrease in alpha diversity

309
Q

What do we need to consider when treating the microbiome with antibiotics ?

A

careful selection of antibiotics to minimise shifts in microbiota
avoid repeated use of single antibiotics
repopulate the gut with good bacteria

310
Q

What are prebiotics ?

A

designed to feed good bacteria
encourage good bacteria to take over
eg. amino acids

311
Q

What are probiotics ?

A

deliver microorganims to the gut

not very regulated

312
Q

What is a foecal microbiotia transplantation ?

A

take good bacteria and insert into infected people

results arent long lasting

313
Q

What are the major dental plaque related diseases ?

A

periodontitis

dental caries

314
Q

What is the specific plaque hypothesis ?

A

diseases are caused by a single microorganism

315
Q

What is the non specific plaque hypothesis ?

A

diseases are caused by the amount of plaque

316
Q

What is the ecological plaque hypothesis ?

A

diseases are caused by the interactions of specific microorganisms in the microbial community

317
Q

What is the process of dental caries ?

A

health
subsurface demineralisation
white spot lesion
cavitation

318
Q

What does the ecological plaque hypothesis state about dental caries aetiology ?

A 
stress
excess sugar 
acid production 
low pH 
leads to environmental and ecological change 
demineralisation
319
Q

What are keystone species ?

A

disproprptionately large effects on the population given their abundance

320
Q

What does a keystone pathogen do ?

A

supports and stabilises the dysbiotic state

triggering an immune response that is overactive and unhelpful

321
Q

What are keystone species associated with ?

A

periodontitis

322
Q

What type of microbiotia is periodontitis initiated by ?

A

synergistic and dysbiotic

323
Q

What does polymicrobial synergy say about periodontitis ?

A

different members of the community have different gene combinations that fulfil roles that allow shaping and survival of a disease provoking microbiotia

324
Q

What is clinical microbiology ?

A

in vitro diagnosis and management of diseases caused my microorganisms

325
Q

What is the role of the clinical microbiology lab ?

A

provide accurate info about the presence or absence of microbes in a patient sample
aid in management
provide info about antimicrobial susceptibility
testing in a clinically relevant time frame

326
Q

What makes a good diagnostic test in microbiology ?

A

specific
sensitive
time is relevant
easy to use

327
Q

What does specificity mean with clinical testing ?

A

no false positives

provides high level of confidence with results

328
Q

What does sensitivity mean ?

A

detect low levels of cells and viral particles

329
Q

What can we use direct microscopy for ?

A

visualise microorganisms
lacks sensitivity and specificity
requires large amount of pathogen
use gram stain and morphology

330
Q

How can we identify bacteria based on isolation techniques ?

A

bacteria have different growth requirements like oxygen/temperature
use specialised media

331
Q

How can we use antibodies to test for pathogens ?

A

detect antigens using latex particles coated in antibod, leads to agglutination, useful if patient has already had antibiotics
take blood samples and look for evidenc eof antibodies to certain diseases- eg.MMR

332
Q

How does PCR happen ?

A

heat DNA to denature it
separate strands
anneal primers at lower temp
taq polymerase binds and amplifies DNA

333
Q

What are the advantages of PCR based testing ?

A

rapid
detect different pathogens in the same tube
increased sensitivity
specific

334
Q

For which disease is PCR testing standard ?

A

whooping cough

bordetella pertusis

335
Q

How do you carry out the gram stain ?

A

apply crystal violet
Add iodine
wash with alcohol
counter stain with safranin

336
Q

What is the oxidase test ?

A

oxidase positive bacteria contain cytochrome C oxidase
this uses oxygen for energy production in the etc
test for the presence of cytochrome C oxidase

337
Q

Which bacteria are usually OX+ ?

A

gram negative

helicobacter pylori etc

338
Q

What are the limitations of culture based methods ?

A

some organisms grow slowly, difficult to grow or dont grow at all
not helpful if patient has already taken antibiotics

339
Q

What is syndromic testing ?

A

testing for multiple pathogens at the same time

340
Q

How do you carry out the urease test ?

A

mix bacteria with urease broth (urea and phenol red)
broth is mix of urea and indicator
if bacteria have the enzyme urease they will break down the urea into ammonia - colour change to yellow

341
Q

What is the catalase test ?

A

place hydrogen peroxide on slide
add loopful of bacteria
if the bacteria have catalase they will break the hydrogen peroxide down into oxygen and water

342
Q

How is urease relevant to dental plaque ?

A

having urease means that bacteria can convert urea toa ammonia and raise the pH - this can protect against caries

343
Q

How do helicobacter pylori use urease ?

A

ammonia produced neutralises the stomach acid and allows the bacterium to survive ad cause stomach ulcers

344
Q

What is the DNase test ?

A

degradation of DNA releases free nucleotides

this turns toludine blue pink

345
Q

What is the coagulase test ?

A

latex particles are coated with fibrinogen if the bacteria have coagulase - bind the fibrinogen into a clot. Visible as agglutination of the blue particles

346
Q

What is the appearance of Staphylococus Aureus ?

A

appears a bunch of grapes - cocci shaped

347
Q

Is S.Aureus gram positive or negative ?

A

gram positive- stains purple due to thick peptidoglycan layer

348
Q

Where can you find S.aureus ?

A

anterior nares, nasopharynx and skin

349
Q

Is S.aureus catalase positive or negative ?

A

Catalase positive- can liberate oxygen from hydrogen peroxide

350
Q

Is S.aureus commensal ?

A

it can be commensal but is associated with infection so can be opportunistic

351
Q

Is S.aureus coagulase positive ?

A

coagulase positive

352
Q

Is S.aureus DNase positive ?

A

yes- helps it escape from host DNA released to trap pathogens

353
Q

What is a major problem with S.aureus ?

A

MRSA

354
Q

What are some diseases S.aureus can cause ?

A

food poisoning, toxic shock syndrome

355
Q

What are streptococcus salivarius ?

A

oral streptoccoci that are potentially pathogenic - can cause infective endocarditits

356
Q

How is S.salivarius importnat in dental caries ?

A

it can produce acid from sugar and has increased numbers at carious lesions

357
Q

is S.salivarius urease positive ?

A

yes- urease converts urea to ammonia which can protect against dental caries

358
Q

Is S.Salivarius gram positive ?

A

yes gram positive-stains purple

359
Q

What is the shape of S.salivarius ?

A

cocci shaped but forms strips of streps

360
Q

Why does S.salivarius produce a greenish tinge on blood agar ?

A

they produce hydrogen peroxide and lack catalase

361
Q

Where can you mainly find e.coli ?

A

enteric

362
Q

Is e.coli harmful ?

A

it is commonly used as a lab model organism

some strains are pathogenic

363
Q

Which strains of e.coli are pathogenic ?

A

those that possess the 157 version of the O antigen- part of the LPS

364
Q

What common diseases does e.coli cause ?

A

diarrhoea and vomiting

UTIs

365
Q

Are e.coli gram negative or positive ?

A

gram negative

366
Q

What is the shape of e.coli ?

A

rod shaped bacillus

367
Q

Is e.coli motile ?

A

yes and it has fimrbriae

368
Q

Does e.coli ferment lactose ?

A

yes

369
Q

Is e.coli catalase postive ?

A

yes - gives it protection against hydrogen peroxide

370
Q

What is selective media ?

A

designed to allow the growth of selected bacteria whilst inhibiting most

371
Q

What is indicator media ?

A

chromogenic tests that allow us to identify particular media

372
Q

How can we use carbohydrate profiles to detect bacteria ?

A

bacteria ferment sugars into acids

overnight incubation turns a red indicator to yellow in presence of acid

373
Q

What are the advantages of broth culture ?

A 
easy 
large amounts of cells can be cultured 
economic 
in broth culture all cells are growing whilst in agar only cells at the edges are growing 
use for total viable counts
374
Q

What are the disadvantages of broth culture ?

A

distinguish between different bacteria

difficult to get a colony of one type

375
Q

What is XLD agar ?

A

used for the identification of enteric bacteria because it contains sodium desoxycholate - inhibits gram positive bacteria

376
Q

What is CLED agar used for ?

A

non selective and used for culture of bacteria from urine specimens

377
Q

What is blood agar ?

A

uses haemolysis to idnetify different bacteria from alpha, beta or gamma haemolysis

378
Q

What is staph agar ?

A

a selective medium based on a high salt concentration

staphyloccoci are resistant to salt

379
Q

Which stains can you use to make bacteria visible under a microscope ?

A

gram stain

ziehl neelson

380
Q

Which samples is microsocopy useful for ?

A

samples that otherwise wouldnt contain bacteria

381
Q

What is the structure of LPS ?

A

consists of a lipid, core polysaccharide and O-polysaccharide

382
Q

How is it better to detect diseases ?

A

by tracking antigens in pathogens rather thatn identiying the pathogen

383
Q

How can we use latex agglutination to detect antigens ?

A

coloured latex beads have antibody specific for an antigen attached
mix suspension of bacterial cells with beads and antibody will bind to antigen if present casing agglutination

384
Q

Is N.Gonnorhoeae gram positive or negative ?

A

gram negative- stains pink

385
Q

What is the advantage of N.gonorrhoaeae being encapsulated ?

A

the polysaccharide layer limits the ability of phagocytes to engulf it

386
Q

Is N.gonoorhoaea DNase positive ?

A

yes it can break down host bacteria and trap the pathogen

387
Q

What is the shape of N.Gonorrhoae ?

A

diploccocus

388
Q

Is N.Gonorrhoaeae catalase positive ?

A

yes

389
Q

What does it mean if N.gonorrhoeae is fastidious ?

A

has complex nutrtitional requirement that requires blood and amino acids to groq

390
Q

Is Gonoorhoaea an STI ?

A

yes- 2nd most common after chlamidya

391
Q

Which areas does N.gonorrhoeae affect ?

A

genitals
rectum
eyes
mucous membranes

392
Q

What is the mechanism of action of N.gonorrhoeae ?

A

bacteria adheres to cells via pilli
proteases are produced to digest epithelial cells
trigger inflammatory response- leads to damage in the fallopian tubes and leads to infertility.

393
Q

What are the virulence factors of S.Aureus ?

A

potent exotoxins- TSSt1 leading to toxic sock syndrome

394
Q

What are the virulence factors in N. gonorrhoae ?

A

outer membrane porin that protects against phagocytes

395
Q

What are the transmission and symptoms of N.gonorrhoeae ?

A

green discharge, lower abdomen pain and burning when urinating
transmitted by unprotected sex and childborth

396
Q

Is L.pneumophilia gram negative or positive ?

A

gram negative- stains pink

397
Q

What is the shape of L.pneumophilia ?

A

small short rod with flagella

398
Q

Where can you find L.pneumophilia ?

A

water environments
aerosols
dental water lines- run water though every morning to get rid of stagnant water

399
Q

What are the virulence factors of L.pneumophilia ?

A

secretes molecules that protect it against phagocytes

400
Q

What are the diseases that L.pneumophilia causes ?

A

Legionnaires disease- lethal pneumonia

pontiac fever

401
Q

How can L.pneumophilia lead to lung damage ?

A

results in lysis of the macrophage- immune system unable to clear- leading to lung damage

402
Q

How can we diagnose infection with L.Pneumophilia ?

A

Rapid diagnosis with PCR

403
Q

Is C.diificile gram positive or negative ?

A

gram positive- stains purple

404
Q

What does C.dificile do ?

A

colonises intestinal epithelium leading to diarrhoea, abdominal pain
pseudomembrane formation in the pharynx
releases toxins

405
Q

What are the virulence factors of C.difficile ?

A

toxins that have enterotoxic and cytotoxic activity
toxins A and B
proinflammatory interluekins and TNF

406
Q

Where can you find C.difficile ?

A

digestive system
elderly
immunosupressed

407
Q

Is N.Gonnorhoeae gram positive or negative ?

A

gram negative- stains pink

408
Q

What is the advantage of N.gonorrhoaeae being encapsulated ?

A

the polysaccharide layer limits the ability of phagocytes to engulf it

409
Q

Is N.gonoorhoaea DNase positive ?

A

yes it can break down host bacteria and trap the pathogen

410
Q

What is the shape of N.Gonorrhoae ?

A

diploccocus

411
Q

Is N.Gonorrhoaeae catalase positive ?

A

yes

412
Q

What does it mean if N.gonorrhoeae is fastidious ?

A

has complex nutrtitional requirement that requires blood and amino acids to groq

413
Q

Is Gonoorhoaea an STI ?

A

yes- 2nd most common after chlamidya

414
Q

Which areas does N.gonorrhoeae affect ?

A

genitals
rectum
eyes
mucous membranes

415
Q

What is the mechanism of action of N.gonorrhoeae ?

A

bacteria adheres to cells via pilli
proteases are produced to digest epithelial cells
trigger inflammatory response- leads to damage in the fallopian tubes and leads to infertility.

416
Q

What are the virulence factors of S.Aureus ?

A

potent exotoxins- TSSt1 leading to toxic sock syndrome

417
Q

What are the virulence factors in N. gonorrhoae ?

A

outer membrane porin that protects against phagocytes

418
Q

What are the transmission and symptoms of N.gonorrhoeae ?

A

green discharge, lower abdomen pain and burning when urinating
transmitted by unprotected sex and childborth

419
Q

Is L.pneumophilia gram negative or positive ?

A

gram negative- stains pink

420
Q

What is the shape of L.pneumophilia ?

A

small short rod with flagella

421
Q

Where can you find L.pneumophilia ?

A

water environments
aerosols
dental water lines- run water though every morning to get rid of stagnant water

422
Q

What are the virulence factors of L.pneumophilia ?

A

secretes molecules that protect it against phagocytes

423
Q

What are the diseases that L.pneumophilia causes ?

A

Legionnaires disease- lethal pneumonia

pontiac fever

424
Q

How can L.pneumophilia lead to lung damage ?

A

results in lysis of the macrophage- immune system unable to clear- leading to lung damage

425
Q

How can we diagnose infection with L.Pneumophilia ?

A

Rapid diagnosis with PCR

426
Q

Is C.diificile gram positive or negative ?

A

gram positive- stains purple

427
Q

What does C.dificile do ?

A

colonises intestinal epithelium leading to diarrhoea, abdominal pain
pseudomembrane formation in the pharynx
releases toxins

428
Q

What are the virulence factors of C.difficile ?

A

toxins that have enterotoxic and cytotoxic activity
toxins A and B
proinflammatory interluekins and TNF

429
Q

Where can you find C.difficile ?

A

digestive system
elderly
immunosupressed

430
Q

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

A

enterotoxin- a preformed toxin so symptoms occur faster

431
Q

Name 3 different characteristics of bacterial cells that allow us to identify them by microscopy ?

A

shape
colour
motility- flagella

432
Q

What type of substance is the target of diagnostic tests for clostridium difficile ?

A

clostridium toxin- use antobody based detection for toxin in faeces

433
Q

Is brillialnce candida agar selective or indicative ?

A

both

434
Q

What changes occur following the growth of beta haemolytic bacteria ?

A

lysis of red blood cells

bleaching of agar- becomes straw coloured and translucent

BDS stage 2 (28 decks)

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