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Medicine Year 2 5 > Microbiology - basics > Flashcards

Microbiology - basics Flashcards

1
Q

Give 3 gram positive cocci

A
  • ) Staphylococci
  • ) Streptococci
  • ) Enterococci
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2
Q

Give 2 gram negative cocci

A
  • ) Neisseria

- ) Moraxella

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3
Q

Give 3 gram positive bacilli

A
  • ) C. diptheriae
  • ) Listeria monocytogenes
  • ) Clostridia
  • ) Propionibactiera
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4
Q

Give 5 gram negative bacilli

A
  • ) E. coli
  • ) Campylobacter
  • ) Pseudomonas
  • ) Salmonella
  • ) Shigella
  • ) Proteus
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5
Q

What colour does positive gram bacteria stain?

A

Purple

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6
Q

What colour does negative gram bacteria stain?

A

Pink

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7
Q

What is a gram positive anaerobic cocci?

A

Peptostreptococcus

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8
Q

What test do we do to differentiate between streptococcus and staphylococcus?

A

Catalase test

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9
Q

How does streptococcus stain in a catalase test?

A

Negative, no bubbles

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10
Q

How does staphylococcus stain in a catalase test?

A

Positive, bubbles

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11
Q

What test do we do to differentiate streptococcus?

A

Haemolysis on BA

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12
Q

What colour does beta haemolytic strep stain?

A

White/clearing/yellow

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13
Q

What colour does alpha haemolytic strep stain?

A

Green

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14
Q

Give an example of beta haemolytic strep

A

Antigenic group A, B, C, G

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15
Q

Give an example of alpha haemolytic strep

A

Viridans strep

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16
Q

What test do we do to differentiate between alpha haemolytic streps

A

Optochin test

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17
Q

What are the results of the optochin test?

A

Resistant or sensitive

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18
Q

Give an example of a sensitive alpha haemolytic strep

A

S. pneumoniae

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19
Q

What test do we do to differentiate between staphylococcus?

A

Coagulase

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20
Q

What are the results of the coagulase test?

A

Positive or negative

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21
Q

Give an example of a coagulase positive staphylococcus

A

S. aureus

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22
Q

Give an example of a coagulase negative staphyloccocus

A

Coagulase negative staphyloccus

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23
Q

Give an example of an anaerobic gram negative rod

A

B. fragilis

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24
Q

What do we do to differentiate between gram negative bacilli?

A

Lactose fermentation

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25
Q

What are lactose fermenting bacteria?

A

Enterobacteriaceae (coliforms)

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26
Q

Give an example of a lactose fermenting enterobacteriaceae

A

E. coli, Klebsiella

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27
Q

What do we do to distinguish between enterobacteriaceae? (2)

A

Biochemical identification and sensitivity tests

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28
Q

Give an example of a biochemical identification test

A

API strip

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29
Q

Give 2 examples of a non lactose fermenting bacteria

A
  • ) Shigella
  • ) Salmonella
  • ) Pseudomonas
  • ) Proteus
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30
Q

What test do we do distinguish between non lactose fermenting bacteria?

A

Oxidase test

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31
Q

What are the results of the oxidase test

A

Positive and negative

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32
Q

Give an example of an oxidase test negative bacteria

A

Enterobactericeae

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33
Q

Give an example of a non lactose fermenting enterobacteriaceae

A
  • ) Proteus

- ) Shigella

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34
Q

Give an example of a oxidase test positive bacteria

A

Pseudomonas species

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35
Q

What do we do to test pseudomonas species?

A

Anti-pseudomonal sensitivity tests

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36
Q

What colour does a positive coagulase test stain?

A

Gold

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37
Q

What colour does a negative coagulase test stain?

A

White

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38
Q

What colour does non-lactose fermentation stain?

A

Yellow/colourless

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39
Q

What colour does lactose fermentation stain?

A

Pink

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40
Q

What colour does a positive oxidase test stain?

A

Purple

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41
Q

What colour does a negative oxidase test stain?

A

Not purple/no change

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42
Q

Define pathogen

A

An organism that causes/is capable of causing disease

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43
Q

Define commensal

A

An organism which colonises the host but causes no disease in normal circumstances

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44
Q

Define opportunist pathogen

A

A microbe that only causes disease if host defences are compromised

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45
Q

Define virulence/pathogenicity

A

The degree to which a given organism is pathogenic

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46
Q

Define asymptomatic carriage

A

When a pathogen is carried harmlessly at a tissue site where it causes no disease

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47
Q

Give 2 colonisation factors

A

-) Adhesions
-) Invasins
-) Nutrient acquisition
-) Defence
Etc

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48
Q

Define toxins

A

Effectors that are usually secreted proteins that cause damage and subversion

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49
Q

What are the 2 main shapes of bacteria?

A

Cocci (round) and bacilli (rod)

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50
Q

Why does a positive gram stain response occur?

A

Stain is able to fix to the single membrane cell wall on a gram positive bacteria

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51
Q

Why does a negative gram stain occur?

A

Stain cannot fix due to 2 membranes on gram negative bacteria

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52
Q

Give 2 types of bacterial toxins

A
  • ) Endotoxin

- ) Exotoxin

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53
Q

Give 3 features of an exotoxin

A
  • ) Made up of protein
  • ) Specific action
  • ) Labile to heat
  • ) Strong antigenicity
  • ) Produced by mostly gram +ve
  • ) Convertible to toxoid
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54
Q

Give 3 features of an endotoxin

A
  • ) Made up of lipopolysaccharide, LPS
  • ) Non-specific action
  • ) Stable to heat
  • ) Weak antigenicity
  • ) Produced by mostly gram –ve
  • ) Not convertible to toxoid
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55
Q

What is a toxoid?

A

A toxin treated so that it loses its toxicity but retains its antigenicity

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56
Q

Give 3 ways in which bacteria can get genetic variation

A
  • ) Mutations
  • ) Swap bits of DNA with environment (via plasmids)
  • ) Gene transfer
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57
Q

Give 3 ways in which gene transfer can occur

A
  • ) Transformation, via plasmid
  • ) Transduction, via virus
  • ) Conjugation, via sex pilus
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58
Q

What is are plasmids?

A

Autonomously replicating pieces of DNA

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59
Q

What is coagulase?

A

An enzyme produced by bacteria that clots blood plasma by forming a fibrin clot around bacteria, may protect it from phagocytosis

60
Q

Give 3 virulence factors of staphylococcus

A
  • ) Pore forming toxins
  • ) Proteases
  • ) Toxic shock syndrome
  • ) Protein A
61
Q

Give 3 virulence factors of streptococcus pyogenes

A
  • ) Surface factors (capsule, M protein)
  • ) Enzymes
  • ) Toxins
62
Q

Give 3 virulence factors of streptococcus pneumoniae

A
  • ) Thick capsule
  • ) Inflammatory wall constiuents
  • ) Cytotoxin
63
Q

What is the most virulent group of viridian’s streptococci?

A

Milleri

64
Q

What plate does haemolysis staining us?

A

Red blood agar

65
Q

What is Lancefield typing?

A

Bacteria are grouped according to carbohydrate antigens on cell surfaces

66
Q

What indicates recognition on a Lancefield typing test?

A

Clumping

67
Q

What does ASLO stand for?

A

Anti-streptolysin O

68
Q

What do both gram negative and positive bacteria contain?

A

Peptidoglycan

69
Q

What plate do enterobacteria grow on?

A

MacConkey agar

70
Q

What are enterobacteria (coliforms)?

A

Gamma proteobacteria

71
Q

Give 3 examples of gamma proteobacteria

A
  • ) E. coli
  • ) Shigella
  • ) Salmonella enterica
  • ) Proteus mirabilis
  • ) Klebsiella pneumoniae
  • ) Vibrio cholera
  • ) Pseudomonas aeruginosa
  • ) Haemophilus influenza
  • ) Legionella pneumoniae
72
Q

Give 2 examples of beta proteobacteria

A
  • ) Bordetella pertussis

- ) Neisseria (meningitides and gonorrhoea)

73
Q

What is the organism what causes pertussis?

A

Bordetella pertussis

74
Q

Give 2 examples of epsilon proteobacteria

A
  • ) Campylobacter

- ) Helicobacter pylori

75
Q

Why is phagocytosis of fungi hard?

A

They have a well defined cell wall made up of chitins and polysaccharides

76
Q

Give 3 ways we can classify fungi

A
  • ) Moulds
  • ) Yeasts
  • ) Dimorphic
77
Q

How do fungi move?

A
  • ) Growth

- ) Spores

78
Q

Where are fungi found?

A
  • ) Food
  • ) Soils
  • ) Animal faeces
79
Q

What is the plasma membrane of a fungal cell made up of?

A

Ergosterol

80
Q

How do yeasts reproduced?

A

Asexual budding

81
Q

How do dimorphic fungi grow, depending on their location/temperature?

A
  • ) Tissue - yeasts

- ) In vitro at room temperature - moulds

82
Q

What are moulds also known as?

A

Filamentous fungi

83
Q

Are fungi eukaryotic or prokaryotic?

A

Eukaryotic

84
Q

What 3 levels of infection can fungi cause?

A
  • ) Superficial
  • ) Subcutaneous
  • ) Systemic
85
Q

Give an example of a superficial fungal infection

A
  • ) Skin, nail, hair infection
  • ) Ringworm/athlete’s foot
  • ) Yeast infection/thrust
86
Q

Give an example of a subcutaneous fungal infection

A
  • ) Chromomycosis

- ) Mycetoma

87
Q

Give an example of a systemic fungal infection

A
  • ) Usually in immunocompromised

- ) Opportunistic - aspergillus niger

88
Q

What are mycobacteria?

A

Aerobic, non-spore forming, non-motile bacilli

89
Q

Why can mycobacteria survive inside macrophages even in a low pH environment?

A

High cell wall content of high molecular weight lipids

90
Q

What are mycobacteria that stain with Ziehl-Nielsen?

A

Acid fast bacilli

91
Q

What does the high cell wall content in mycobacteria lead to?

A

SLOW:

  • ) Reproduce
  • ) Grow
  • ) Culture
  • ) Respond to treatment
92
Q

Give 2 diseases caused by mycobacteria

A
  • ) TB
  • ) Leprosy
  • ) Disseminated infection in AIDS
93
Q

What do highly stimulated macrophages become?

A

Epithelioid cells

94
Q

What can epithelioid cells fuse to become?

A

Langhans giant cells, giant multinucleate cells

95
Q

What occurs if the central tissue of a granulomata necroses in TB?

A

Caseating granuloma

96
Q

What is the causative organism of TB?

A

Mycobacterium tuberculosis

97
Q

What is the causative organism of leprosy?

A

M. leprae

98
Q

What are protozoa?

A

Single celled eukaryotic organisms

99
Q

What are the 2 stages of protozoa?

A
  • ) Proliferative stage, tropozoite

- ) Dormant stage, cyst

100
Q

Give 4 of the 5 main types of protozoa

A
  • ) Flagellates
  • ) Amoebae
  • ) Microsporidia
  • ) Ciliates
  • ) Sporozoa
101
Q

What type of protozoa is giardia lambia?

A

Flagellate

102
Q

What type of protozoa is malaria?

A

Sporozoa

103
Q

What is malaria transmitted by?

A

Bite of a female anopheles mosquito

104
Q

When should we consider malaria?

A

Fever and exotic travel

105
Q

Where do viruses grow?

A

Inside living cells

106
Q

What is the structure of a virus?

A
  • ) Outer protein coat (capsule)
  • ) Sometimes surrounded by a lipid envelope
  • ) Have RNA/DNA
107
Q

Where do viruses reproduce?

A

Inside cells

108
Q

What do the proteins on viruses function as? (2)

A
  • ) Enzymes inside the cell

- ) Allow attachment to complementary receptors on susceptible host cell plasma membranes

109
Q

What 2 shapes can viruses be?

A

Helical or polyhedral

110
Q

What are the 6 stages of viral replication?

A

1) Attachment
2) Cell entry
3) Interaction with host cells
4) Replication
5) Assembly
6) Release

111
Q

Give 4 ways in which viruses cause damage

A
  • ) Direct destruction of host cells
  • ) Modification of host cell structure or function (physical/functional)
  • ) Over-reactivity of host as response to infection, immune pathological damage
  • ) Cell proliferation and cell immortalisation
  • ) Evasion of extracellular and intracellular host defects (persistence/variability)
112
Q

Give 2 ways in which viruses are variable

A
  • ) Surface proteins/antigens

- ) Formation of quasi-species

113
Q

What are interferons?

A

Naturally occurring antivirals

114
Q

What are the 3 types of worms?

A
  • ) Nematodes (round)
  • ) Trematodes (flat, flukes)
  • ) Cestodes (tape)
115
Q

What do worms produce which may cause disease?

A

Larvae or eggs

116
Q

What is the pre-patent period?

A

Interval between infection and appearance of eggs in stol

117
Q

How do we diagnose a worm infection?

A

Microscopy

118
Q

How are intestinal nematodes transmitted?

A

Oro-faecally via eggs/larvae that have developed in the soil

119
Q

What is the most common cause of iron deficiency anaemia?

A

Hookworm

120
Q

Where are trematodes found?

A

Blood, liver lungs, bowel

121
Q

What is the intermediate host of flukes?

A

Snails

122
Q

What is an antibiotic?

A

An agent produced by micr-organism that kill or inhibit the growth of other microorganism in high dilution

123
Q

How do antibiotics work?

A

By binding to a target site on a bacterium

124
Q

What organism is a risk with the use of antibiotics?

A

C. difficile

125
Q

What are the 2 main types of antibiotic?

A
  • ) Bacteriostatic

- ) Bactericidal

126
Q

How do bacteriostatic antibiotics work?

A

Prevents growth of bacteria, MIC required

127
Q

How do bactericidal antibiotics work?

A

Kill bacteria, MBC required

128
Q

What does MBC stand for?

A

Minimal bactericidal concentration

129
Q

What does MIC stand for?

A

Minumum inhibitory concentration

130
Q

What are the 2 major determinant of antibacterial effects?

A
  • ) Concentration

- ) Time remains at binding sites

131
Q

What are the 4 parts of pharmacokinetics?

A
  • ) Release
  • ) Absorption
  • ) Distribution
  • ) Elimination (metabolism/excretion)
132
Q

Give 3 considerations for an antibiotic’s distribution

A
  • ) BBB
  • ) pH of site
  • ) Lipid solubility
  • ) Half life
  • ) Safe for patient? (allergies, liver function, pregnancy)
133
Q

Give 3 ways in which the bacteria can prevent the antibiotic from working

A
  • ) Changing target
  • ) Destroying antibiotic
  • ) Preventing access
  • ) Removing antibiotics from bacteria
  • ) Resistance
134
Q

How do we visualise viruses?

A

Electron microscopy

135
Q

What does PCR stand for?

A

Polymerase chain reaction

136
Q

Which Igs appear when in an infection?

A
  • ) IgM - immediate

- ) IgG - later, stays for longer

137
Q

How is a gram stain performed? (5)

A
  • ) Fixation of sample
  • ) Crystal violet added
  • ) Iodine treatment
  • ) Decolourisation
  • ) Safranin counter stain
138
Q

How does a catalase test work?

A

Looks at whether O2 can be reduced by superoxide dismutase to produce H2O2

139
Q

How does a coagulase test work?

A

Coagulase activates prothrombin to convert fibrinogen to fibrin

140
Q

How does haemolysis work?

A

Looks at ability of bacteria to break down RBCs in blood agar

141
Q

What are the 3 results of haemolysis, and why?

A

Alpha - oxidation, green
Beta - lysis, clear
Gamma - nothing, unchanged

142
Q

How do we detect a cytopathic effect in viruses?

A

Culture virus in cell, monitor effects

143
Q

What characteristic of fungi do antifungals target?

A

Ergesterol plasma membranes

144
Q

Why is it difficult to develop treatments for fungal infections?

A

They are eukaryotic/similar RNA and DNA synthesis

145
Q

Why do fungi rarely cause serious disease?

A

They cannot survive above 37 degrees and so are eradicated by fever

146
Q

Name 2 differences between properties of gram negative and positive bacteria

A
  • ) Positive have single cell wall, negative have double
  • ) Positive have small peptidoglycan area whereas negative have large
  • ) Negative produce endotoxins, positive do not
147
Q

TB is treated with 4 antibiotics for 6 months, explain why the treatment is so long and why 4 antibiotics are used (2)

A

Duration - TB replicates slowly

Combined antibiotics - to target all mutations

Medicine Year 2 5 (17 decks)

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