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Medical microbiology and infectious diseases > Week 13 > Flashcards

Week 13 Flashcards

(66 cards)

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1
Q

Prokaryotes vs Eukaryotes
Which are bigger?

A

Eukaryotes

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2
Q

Prokaryotes vs Eukaryotes
Which do not have organelles?

A

prokaryotes

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3
Q

Prokaryotes vs Eukaryotes
Which are more likely to be multicellular?

A

Eukaryotes

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4
Q

What is prokaryotic DNA like?

A

Closed circular DNA- nucleoid

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5
Q

What do eukaryotes have that prokaryotes do not?

A

Organelles, chromosomes, histones, introns

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6
Q

What are the four shapes bacteria can take?

A

Rods
Spheres
Spirals
Threads/filaments

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7
Q

What type of bacteria are rod shaped?

A

Bacilli

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8
Q

What type of bacteria are sphere shaped?

A

coccus

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9
Q

What are endospores?

A

Intracellular spores produced by Gram +ve bacteria as a survival mechanism

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10
Q

What are 2 structural features of an endospore?

A

highly retractile
thick walls

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11
Q

Give two examples of bacteria that produce endospores?

A

Bacillus
Clostridium

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12
Q

What gram is Clostridium? Where does it come from?

A

Anaerobic, Gram +ve bacteria
Inhabits soil and intestinal tracts of animals

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13
Q

In a gram stain, which bacteria is stained pink and which is stained purple?

A

Gram +ve …….. Purple (take up gram stain)
Gram -ve ……….Pink (take up secondary stain)

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14
Q

Give an example of Gram +ve bacteria?

A

Streptococcus sp

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15
Q

Give an example of Gram -ve bacteria?

A

Escherichia coli

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16
Q

Bacterial envelope of Gram +ve bacteria

A

Peptidoglycan thick outer membrane

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17
Q

Bacterial envelope of Gram -ve bacteria

A

Peptidoglycan thin sandwich layer

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18
Q

Which Gram bacteria is more antibiotic resistant and why?

A

Gram -ve
They’re more restrictive about what enters the cell due to double membrane and porin channels. Molecules over 700 daltons can’t enter and can downregulate porins. Antibiotic is less likely to enter the bacteria.

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19
Q

How is peptidoglycan made up?

A

NAG and NAM joined by 1,4 glycosidic bond

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20
Q

L and D amino acids present in peptidoglycan, what’s the difference?

A

D amino acids resist peptide breakdown, so have more rigidity and don’t wear.

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21
Q

Which Gram bacteria have teichoic and lipoteichoic acids present?

A

Gram +ve

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22
Q

Which Gram bacteria have O specific side chains present?

A

Gram -ve

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23
Q

Pentaglycine bridges

A

Bridge containing 5 glycine molecules in Gram +ve bacteria

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24
Q

Peptidoglycan polymerisation

A

monomers joined by more beta 1,4 glycosidic bonds

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25
How can an antibiotic cause cytolysis?
By preventing crosslinking of peptidoglycan
26
What is Gram+ve peptidoglycan crosslinking like?
Pentaglycine cross-links, very ordered and rigid
27
What is Gram-ve peptidoglycan crosslinking like?
Cross links between tetrapeptide chains, less rigid and more spaced out
28
Teichoic acids
Alcohols linked by phosphate groups
29
What charge are phosphate groups?
-ve
30
What are the two types of teichoic acid?
Ribitol and glycerol
31
What is a lipoplysaccharide (LPS)?
Gram -ve bacterial endotoxin
32
What are LPS made up of?
Hexose sugar + O specific chain + 2 heptose sugars + tentacles to anchor it in the membrane
33
Describe an O specific chain
Very variable allows identification of species and strain of bacteria
34
Capsule vs slime
Capsule=lo water content Slime=hi water content
35
How does a cell become motile?
Flagellum
36
How does the basal apparatus work?
Protein gradient across bacterial membrane rotates basal apparatus causing the flagellum to move
37
Name the type of bacteria that have flagellum: 1 2 Many from one end everywhere
1=polar 2=amphitrichous Many from one end= lopotrichous everywhere= petritrichous
38
How do Gram +ve and -ve crosslinking differ?
Gram+ve.........pentaglycine cross bridges Gram-ve...........DAP cross linking
39
Which Gram has teichoic acids and which has LPS?
Gram+ve.........teichoic acid Gram-ve...........LPS
40
4 types of culture media?
Rich Medium Selective Media Differential media Enrichment media
41
Rich Medium
Grows everything
42
Selective Media
eg. bile salts kill bacteria not from the gut
43
Differential media
Identifies different strains/ species based on divergent metabolic processes
44
Enrichment media
Presence of particular growth factors allows growth of fastidious organisms
45
How does blood agar and haemolysis help differentiate bacteria?
What effect the bacteria has on the blood indicates the type of bacteria
46
What effect does strep A have on blood agar?
Clears agar
47
What effect does strep B have on blood agar?
Partially clears agar
48
What effect does Streptococcus pneumoniae have on blood agar?
Dark green cloudy
49
How does catalase help with biochemical differentiation?
Causes fizzing if Gram +ve due to breakdown of h2o2
50
Staph vs Strep Location?
Staph=skin Strep=respiratory
51
How does coagulase help with biochemical differentiation?
Can indicate the presence of pathogenic s.aureus by causing the clotting of blood plasma
52
How do The IMVic test and API strip help differentiate bacteria?
Identifies the presence of enzymes or metabolic pathways in a bacteria. Then add up the scores to find which species of bacteria is present
53
Define species
Collection of strains sharing properties that differ significantly from other strains
54
Define strain
Clonally identical descendants from single pure culture
55
What is serology?
Using antibodies to identify antigen of pathogen (agglutination occurs where bacteria clump into beads with antibodies that match their antigens)
56
Differentiation by serotype: O antigens
Gram -ve, LPS side chains
57
Differentiation by serotype: K antigens
capsular monomers
58
Differentiation by serotype: H antigens
Flagellar proteins
59
How does CHROM agar work?
Requires culture from clinical samples (UTI's) Grown as a lawn and type of bacteria is identified by it's colour
60
How much bacteria will there be in blood vs urine if a genuine infection is present?
Blood: 10^7 cfu/ml Urine: 10^2 cfu/ml
61
Why is BactAlert not great?
Many false positives Still have to plate out to identify type
62
MALDI-TOF (mixed assissted laser desorption/ ionisation time of flight spectroscopy)
Mass spectrometry calibrated with many bacterial samples
63
How does PCR allow identification of MRSA?
MRSA (methilin resistant s.aereus) via mec A gene
64
RAPD PCR (Random Amplified Polymorphic PCR)
Makes 'fingerprint' for an organism, helps to discover relatedness of strains
65
MLST (Multi Locus Sequence Typing)
Sequencing DNA of the PCR product. Primers specifically target a sequence that all species have, then 'allele numbers' identify the organism
66
Number of Sequence Nucleotide Polymorphisms (SNPs)
Dictates distance on the graph, allowing whole genome sequencing to identify source of the outbreak

Medical microbiology and infectious diseases (10 decks)

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