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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
What are lactose fermenting bacteria?
Enterobacteriaceae (coliforms)
26
Give an example of a lactose fermenting enterobacteriaceae
E. coli, Klebsiella
27
What do we do to distinguish between enterobacteriaceae? (2)
Biochemical identification and sensitivity tests
28
Give an example of a biochemical identification test
API strip
29
Give 2 examples of a non lactose fermenting bacteria
- ) Shigella - ) Salmonella - ) Pseudomonas - ) Proteus
30
What test do we do distinguish between non lactose fermenting bacteria?
Oxidase test
31
What are the results of the oxidase test
Positive and negative
32
Give an example of an oxidase test negative bacteria
Enterobactericeae
33
Give an example of a non lactose fermenting enterobacteriaceae
- ) Proteus | - ) Shigella
34
Give an example of a oxidase test positive bacteria
Pseudomonas species
35
What do we do to test pseudomonas species?
Anti-pseudomonal sensitivity tests
36
What colour does a positive coagulase test stain?
Gold
37
What colour does a negative coagulase test stain?
White
38
What colour does non-lactose fermentation stain?
Yellow/colourless
39
What colour does lactose fermentation stain?
Pink
40
What colour does a positive oxidase test stain?
Purple
41
What colour does a negative oxidase test stain?
Not purple/no change
42
Define pathogen
An organism that causes/is capable of causing disease
43
Define commensal
An organism which colonises the host but causes no disease in normal circumstances
44
Define opportunist pathogen
A microbe that only causes disease if host defences are compromised
45
Define virulence/pathogenicity
The degree to which a given organism is pathogenic
46
Define asymptomatic carriage
When a pathogen is carried harmlessly at a tissue site where it causes no disease
47
Give 2 colonisation factors
-) Adhesions -) Invasins -) Nutrient acquisition -) Defence Etc
48
Define toxins
Effectors that are usually secreted proteins that cause damage and subversion
49
What are the 2 main shapes of bacteria?
Cocci (round) and bacilli (rod)
50
Why does a positive gram stain response occur?
Stain is able to fix to the single membrane cell wall on a gram positive bacteria
51
Why does a negative gram stain occur?
Stain cannot fix due to 2 membranes on gram negative bacteria
52
Give 2 types of bacterial toxins
- ) Endotoxin | - ) Exotoxin
53
Give 3 features of an exotoxin
- ) Made up of protein - ) Specific action - ) Labile to heat - ) Strong antigenicity - ) Produced by mostly gram +ve - ) Convertible to toxoid
54
Give 3 features of an endotoxin
- ) Made up of lipopolysaccharide, LPS - ) Non-specific action - ) Stable to heat - ) Weak antigenicity - ) Produced by mostly gram --ve - ) Not convertible to toxoid
55
What is a toxoid?
A toxin treated so that it loses its toxicity but retains its antigenicity
56
Give 3 ways in which bacteria can get genetic variation
- ) Mutations - ) Swap bits of DNA with environment (via plasmids) - ) Gene transfer
57
Give 3 ways in which gene transfer can occur
- ) Transformation, via plasmid - ) Transduction, via virus - ) Conjugation, via sex pilus
58
What is are plasmids?
Autonomously replicating pieces of DNA
59
What is coagulase?
An enzyme produced by bacteria that clots blood plasma by forming a fibrin clot around bacteria, may protect it from phagocytosis
60
Give 3 virulence factors of staphylococcus
- ) Pore forming toxins - ) Proteases - ) Toxic shock syndrome - ) Protein A
61
Give 3 virulence factors of streptococcus pyogenes
- ) Surface factors (capsule, M protein) - ) Enzymes - ) Toxins
62
Give 3 virulence factors of streptococcus pneumoniae
- ) Thick capsule - ) Inflammatory wall constiuents - ) Cytotoxin
63
What is the most virulent group of viridian's streptococci?
Milleri
64
What plate does haemolysis staining us?
Red blood agar
65
What is Lancefield typing?
Bacteria are grouped according to carbohydrate antigens on cell surfaces
66
What indicates recognition on a Lancefield typing test?
Clumping
67
What does ASLO stand for?
Anti-streptolysin O
68
What do both gram negative and positive bacteria contain?
Peptidoglycan
69
What plate do enterobacteria grow on?
MacConkey agar
70
What are enterobacteria (coliforms)?
Gamma proteobacteria
71
Give 3 examples of gamma proteobacteria
- ) E. coli - ) Shigella - ) Salmonella enterica - ) Proteus mirabilis - ) Klebsiella pneumoniae - ) Vibrio cholera - ) Pseudomonas aeruginosa - ) Haemophilus influenza - ) Legionella pneumoniae
72
Give 2 examples of beta proteobacteria
- ) Bordetella pertussis | - ) Neisseria (meningitides and gonorrhoea)
73
What is the organism what causes pertussis?
Bordetella pertussis
74
Give 2 examples of epsilon proteobacteria
- ) Campylobacter | - ) Helicobacter pylori
75
Why is phagocytosis of fungi hard?
They have a well defined cell wall made up of chitins and polysaccharides
76
Give 3 ways we can classify fungi
- ) Moulds - ) Yeasts - ) Dimorphic
77
How do fungi move?
- ) Growth | - ) Spores
78
Where are fungi found?
- ) Food - ) Soils - ) Animal faeces
79
What is the plasma membrane of a fungal cell made up of?
Ergosterol
80
How do yeasts reproduced?
Asexual budding
81
How do dimorphic fungi grow, depending on their location/temperature?
- ) Tissue - yeasts | - ) In vitro at room temperature - moulds
82
What are moulds also known as?
Filamentous fungi
83
Are fungi eukaryotic or prokaryotic?
Eukaryotic
84
What 3 levels of infection can fungi cause?
- ) Superficial - ) Subcutaneous - ) Systemic
85
Give an example of a superficial fungal infection
- ) Skin, nail, hair infection - ) Ringworm/athlete's foot - ) Yeast infection/thrust
86
Give an example of a subcutaneous fungal infection
- ) Chromomycosis | - ) Mycetoma
87
Give an example of a systemic fungal infection
- ) Usually in immunocompromised | - ) Opportunistic - aspergillus niger
88
What are mycobacteria?
Aerobic, non-spore forming, non-motile bacilli
89
Why can mycobacteria survive inside macrophages even in a low pH environment?
High cell wall content of high molecular weight lipids
90
What are mycobacteria that stain with Ziehl-Nielsen?
Acid fast bacilli
91
What does the high cell wall content in mycobacteria lead to?
SLOW: - ) Reproduce - ) Grow - ) Culture - ) Respond to treatment
92
Give 2 diseases caused by mycobacteria
- ) TB - ) Leprosy - ) Disseminated infection in AIDS
93
What do highly stimulated macrophages become?
Epithelioid cells
94
What can epithelioid cells fuse to become?
Langhans giant cells, giant multinucleate cells
95
What occurs if the central tissue of a granulomata necroses in TB?
Caseating granuloma
96
What is the causative organism of TB?
Mycobacterium tuberculosis
97
What is the causative organism of leprosy?
M. leprae
98
What are protozoa?
Single celled eukaryotic organisms
99
What are the 2 stages of protozoa?
- ) Proliferative stage, tropozoite | - ) Dormant stage, cyst
100
Give 4 of the 5 main types of protozoa
- ) Flagellates - ) Amoebae - ) Microsporidia - ) Ciliates - ) Sporozoa
101
What type of protozoa is giardia lambia?
Flagellate
102
What type of protozoa is malaria?
Sporozoa
103
What is malaria transmitted by?
Bite of a female anopheles mosquito
104
When should we consider malaria?
Fever and exotic travel
105
Where do viruses grow?
Inside living cells
106
What is the structure of a virus?
- ) Outer protein coat (capsule) - ) Sometimes surrounded by a lipid envelope - ) Have RNA/DNA
107
Where do viruses reproduce?
Inside cells
108
What do the proteins on viruses function as? (2)
- ) Enzymes inside the cell | - ) Allow attachment to complementary receptors on susceptible host cell plasma membranes
109
What 2 shapes can viruses be?
Helical or polyhedral
110
What are the 6 stages of viral replication?
1) Attachment 2) Cell entry 3) Interaction with host cells 4) Replication 5) Assembly 6) Release
111
Give 4 ways in which viruses cause damage
- ) 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
Give 2 ways in which viruses are variable
- ) Surface proteins/antigens | - ) Formation of quasi-species
113
What are interferons?
Naturally occurring antivirals
114
What are the 3 types of worms?
- ) Nematodes (round) - ) Trematodes (flat, flukes) - ) Cestodes (tape)
115
What do worms produce which may cause disease?
Larvae or eggs
116
What is the pre-patent period?
Interval between infection and appearance of eggs in stol
117
How do we diagnose a worm infection?
Microscopy
118
How are intestinal nematodes transmitted?
Oro-faecally via eggs/larvae that have developed in the soil
119
What is the most common cause of iron deficiency anaemia?
Hookworm
120
Where are trematodes found?
Blood, liver lungs, bowel
121
What is the intermediate host of flukes?
Snails
122
What is an antibiotic?
An agent produced by micr-organism that kill or inhibit the growth of other microorganism in high dilution
123
How do antibiotics work?
By binding to a target site on a bacterium
124
What organism is a risk with the use of antibiotics?
C. difficile
125
What are the 2 main types of antibiotic?
- ) Bacteriostatic | - ) Bactericidal
126
How do bacteriostatic antibiotics work?
Prevents growth of bacteria, MIC required
127
How do bactericidal antibiotics work?
Kill bacteria, MBC required
128
What does MBC stand for?
Minimal bactericidal concentration
129
What does MIC stand for?
Minumum inhibitory concentration
130
What are the 2 major determinant of antibacterial effects?
- ) Concentration | - ) Time remains at binding sites
131
What are the 4 parts of pharmacokinetics?
- ) Release - ) Absorption - ) Distribution - ) Elimination (metabolism/excretion)
132
Give 3 considerations for an antibiotic's distribution
- ) BBB - ) pH of site - ) Lipid solubility - ) Half life - ) Safe for patient? (allergies, liver function, pregnancy)
133
Give 3 ways in which the bacteria can prevent the antibiotic from working
- ) Changing target - ) Destroying antibiotic - ) Preventing access - ) Removing antibiotics from bacteria - ) Resistance
134
How do we visualise viruses?
Electron microscopy
135
What does PCR stand for?
Polymerase chain reaction
136
Which Igs appear when in an infection?
- ) IgM - immediate | - ) IgG - later, stays for longer
137
How is a gram stain performed? (5)
- ) Fixation of sample - ) Crystal violet added - ) Iodine treatment - ) Decolourisation - ) Safranin counter stain
138
How does a catalase test work?
Looks at whether O2 can be reduced by superoxide dismutase to produce H2O2
139
How does a coagulase test work?
Coagulase activates prothrombin to convert fibrinogen to fibrin
140
How does haemolysis work?
Looks at ability of bacteria to break down RBCs in blood agar
141
What are the 3 results of haemolysis, and why?
Alpha - oxidation, green Beta - lysis, clear Gamma - nothing, unchanged
142
How do we detect a cytopathic effect in viruses?
Culture virus in cell, monitor effects
143
What characteristic of fungi do antifungals target?
Ergesterol plasma membranes
144
Why is it difficult to develop treatments for fungal infections?
They are eukaryotic/similar RNA and DNA synthesis
145
Why do fungi rarely cause serious disease?
They cannot survive above 37 degrees and so are eradicated by fever
146
Name 2 differences between properties of gram negative and positive bacteria
- ) Positive have single cell wall, negative have double - ) Positive have small peptidoglycan area whereas negative have large - ) Negative produce endotoxins, positive do not
147
TB is treated with 4 antibiotics for 6 months, explain why the treatment is so long and why 4 antibiotics are used (2)
Duration - TB replicates slowly | Combined antibiotics - to target all mutations

Medicine Year 2 5 (17 decks)

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