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Medical microbiology and infectious diseases > Week 13 > Flashcards

Week 13 Flashcards

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
Q

How can an antibiotic cause cytolysis?

A

By preventing crosslinking of peptidoglycan

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26
Q

What is Gram+ve peptidoglycan crosslinking like?

A

Pentaglycine cross-links, very ordered and rigid

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27
Q

What is Gram-ve peptidoglycan crosslinking like?

A

Cross links between tetrapeptide chains, less rigid and more spaced out

28
Q

Teichoic acids

A

Alcohols linked by phosphate groups

29
Q

What charge are phosphate groups?

30
Q

What are the two types of teichoic acid?

A

Ribitol and glycerol

31
Q

What is a lipoplysaccharide (LPS)?

A

Gram -ve bacterial endotoxin

32
Q

What are LPS made up of?

A

Hexose sugar + O specific chain + 2 heptose sugars + tentacles to anchor it in the membrane

33
Q

Describe an O specific chain

A

Very variable
allows identification of species and strain of bacteria

34
Q

Capsule vs slime

A

Capsule=lo water content
Slime=hi water content

35
Q

How does a cell become motile?

36
Q

How does the basal apparatus work?

A

Protein gradient across bacterial membrane rotates basal apparatus causing the flagellum to move

37
Q

Name the type of bacteria that have flagellum:
1
2
Many from one end
everywhere

A

1=polar
2=amphitrichous
Many from one end= lopotrichous
everywhere= petritrichous

38
Q

How do Gram +ve and -ve crosslinking differ?

A

Gram+ve………pentaglycine cross bridges
Gram-ve………..DAP cross linking

39
Q

Which Gram has teichoic acids and which has LPS?

A

Gram+ve………teichoic acid
Gram-ve………..LPS

40
Q

4 types of culture media?

A

Rich Medium
Selective Media
Differential media
Enrichment media

41
Q

Rich Medium

A

Grows everything

42
Q

Selective Media

A

eg. bile salts kill bacteria not from the gut

43
Q

Differential media

A

Identifies different strains/ species based on divergent metabolic processes

44
Q

Enrichment media

A

Presence of particular growth factors allows growth of fastidious organisms

45
Q

How does blood agar and haemolysis help differentiate bacteria?

A

What effect the bacteria has on the blood indicates the type of bacteria

46
Q

What effect does strep A have on blood agar?

A

Clears agar

47
Q

What effect does strep B have on blood agar?

A

Partially clears agar

48
Q

What effect does Streptococcus pneumoniae have on blood agar?

A

Dark green cloudy

49
Q

How does catalase help with biochemical differentiation?

A

Causes fizzing if Gram +ve due to breakdown of h2o2

50
Q

Staph vs Strep
Location?

A

Staph=skin
Strep=respiratory

51
Q

How does coagulase help with biochemical differentiation?

A

Can indicate the presence of pathogenic s.aureus by causing the clotting of blood plasma

52
Q

How do The IMVic test and API strip help differentiate bacteria?

A

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
Q

Define species

A

Collection of strains sharing properties that differ significantly from other strains

54
Q

Define strain

A

Clonally identical descendants from single pure culture

55
Q

What is serology?

A

Using antibodies to identify antigen of pathogen (agglutination occurs where bacteria clump into beads with antibodies that match their antigens)

56
Q

Differentiation by serotype: O antigens

A

Gram -ve, LPS side chains

57
Q

Differentiation by serotype: K antigens

A

capsular monomers

58
Q

Differentiation by serotype: H antigens

A

Flagellar proteins

59
Q

How does CHROM agar work?

A

Requires culture from clinical samples (UTI’s) Grown as a lawn and type of bacteria is identified by it’s colour

60
Q

How much bacteria will there be in blood vs urine if a genuine infection is present?

A

Blood: 10^7 cfu/ml
Urine: 10^2 cfu/ml

61
Q

Why is BactAlert not great?

A

Many false positives
Still have to plate out to identify type

62
Q

MALDI-TOF
(mixed assissted laser desorption/ ionisation time of flight spectroscopy)

A

Mass spectrometry calibrated with many bacterial samples

63
Q

How does PCR allow identification of MRSA?

A

MRSA (methilin resistant s.aereus) via mec A gene

64
Q

RAPD PCR
(Random Amplified Polymorphic PCR)

A

Makes ‘fingerprint’ for an organism, helps to discover relatedness of strains

65
Q

MLST
(Multi Locus Sequence Typing)

A

Sequencing DNA of the PCR product.
Primers specifically target a sequence that all species have, then ‘allele numbers’ identify the organism

66
Q

Number of Sequence Nucleotide Polymorphisms (SNPs)

A

Dictates distance on the graph, allowing whole genome sequencing to identify source of the outbreak

Medical microbiology and infectious diseases (5 decks)

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