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Principles > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What do bacteria have instead of a nucleus?

A

Nucleoid- DNA and associated proteins
No nuclear membrane
Co transcription and translation via DNA dependent RNA polymerase

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2
Q

How is the chromosome arranged in a bacteria?

A

Single circular chromosome organised by gyrases

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3
Q

What are DNA gyrases?

A

Essential bacterial enzymes that catalyses the DNA dependant negative super coiling of double stranded closed circular DNA (part of topsomerases)

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4
Q

What are extra chromosomal replications called?

A

Plasmids

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5
Q

Where do most biochemical processes take place in a prokaryote?

A

The cell membrane as tehre are no membrane bound organelles

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6
Q

How is energy generated in a bacterial cell?

A

Electrons are released from high energy compounds in the cytoplasm. They reach the membrane and are passed through a series of electron acceptors.
The energy released from this pumps H+ ions outside of the membrane producing an electrochamical gradient.
Inflow of protons generates ATP.
NB: This occurs on the surface of the cell- therefore if you damage the membrane you will damage/kill the bacteria

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7
Q

What is peptidoglycan made from?

A 
2 Sugars 
NAM = N-acetyl muramic acid
NAG = N-acetyl glucosamine 
and peptide bridges with 5 types of protein 
Repeated polysaccharide structure
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8
Q

Why do bacteria require a cell wall?

A

High osmotic pressure and concentrated cytoplasm

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9
Q

What is the target for penicillin?

A

Peptidoglycan cell wall

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10
Q

Describe the cell wall in a gram positive bacteria?

A

Thick multilayered peptidogylcan
Rope structure
Survive 8-10 atmospheres

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11
Q

Describe the cell wall in a gram negative bacteria?

A

Thin peptidoglycan layer
Survive 5-6 atmospheres
2 cell membranes (inner and outer)
Lipopolysaccharide extensively on outer membrane

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12
Q

What is the role of glycolipids?

A

Lipid A and core polysaccharide

Structural support but also as an antigen, bacterial toxin

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13
Q

What are flagella and fimbrae?

A

Proteinachious extensions

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14
Q

Which bacteria have flagella and what is the function?

A

Both gram positive and gram negative
Huge SA to help with attachment and adhesion of bacteria together
Some inject RNA and toxins
Useful for motility

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15
Q

What is a fimbrae/pillus and which bacteria have which one?

A

Non flagella proteinacious abhendage
Fibrae = gram positive
Pillus = gram negative (=> biofilm formation)
Used for adherence and sex in both

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16
Q

Where does prokaryotic protein synthesis take place and what are the features?

A

Cytoplasmic membrane
Co-transcription/translation
No polyadenylation of transcript (addition of poly A tails to mRNA)
Rapid => higher mutation rate

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17
Q

What is required for binary fission?

A

Food: C, H, O, N, Inorganic salts (metal), Trace elements (Zn, Cu, Mn, Ni) and vitamins (Folic acid and Niacin)
Specific temp, pH, osmotic protection and oxygen concentration

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18
Q

What are the 4 phases of binary fission?

A

1) Lag phase
2) Exponential phase
3) Stationary phase- all nutrients used up
4) Decline phase- bacteria die and produce toxins. No more nutrients

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19
Q

What is a bacteria called that works at low, high and body temp?

A

Low = Psycrophiles
High = Thermophiles
Body temp = mesophiles

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20
Q

What is the preferred pH and osmotic protection for human commensal bacteria?

A
  1. 8-7.2 pH

0. 85% NaCl

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21
Q

What is a microaerophile?

A

A bacterium which requires oxygen at a less than atmospheric pressure

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22
Q

Bacteria can sense there population density. T or F?

A

True

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23
Q

What is multicellularity?

A

Colony development and differentiation

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24
Q

What are planktonic cells?

A

Free flowing bacteria in suspension

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25
Q

What is a biofilm?

A

A group of microorganisms that stick together on a surface

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26
Q

If cocci divide in one plane they produce…?

A

Chains eg Streptococci

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27
Q

If cocci divide in 3 planes they produce…?

A

Clumps eg staph aureus

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28
Q

If cocci divide in right angled planes they produce…?

A

Socina => Perfect packets of 4

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29
Q

What is a bacillus and how are they commonly found?

A

Rod shaped bacterium

Normally gram positive in chains

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30
Q

Give an example of a curved rod bacterium and the gram stain?

A

Vibro Cholerae

Gram negative

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31
Q

Give 2 examples of spiral shaped bacterium?

A 
Rigid = Spirillium 
Flexible = Spirochaete
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32
Q

What is a fusiform bacteria?

A

A long elongated form

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33
Q

What are capsules made from and what is there function?

A

Carbohydrates,

Physical and chemical protection

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34
Q

What are spores?

A

Innert structures resistant to physical and chemical challenge. Resistant to disinfectant so survive a long time outside the body.
Produced by C diff

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35
Q

How are spores produced and released?

A

Binary fission -> Sporulation -> Prespore (dehydrated and condensed) -> endospore -> cell lysis -> germination of spore

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36
Q

What is gram staining?

A

The retention of crystal violet/iodine staining by gram positive bacteria

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37
Q

How is gram staining carried out?

A

1) Add cyrstal violet (the greater the PG the greater the uptake)
2) Add decolouring agent eg ethanol/acetone for 10-15 seconds. Decolourises the cell that has not taken up crystal violet
3) Add water to stop the decolourising process
4) Add the iodine complex to see colourless structures

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38
Q

What are the limitations of gram staining?

A

Not all organisms stain well eg mycobacterium have a lipid rich waxy cell wall, treponema pallidum (causes syphilis

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39
Q

What is an aerobic bacteria?

A

Grows in air/oxygen

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40
Q

What is an obligate aerobe?

A

Must have oxygen

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41
Q

What is an obligate anaerobe?

A

Killed by oxygen.
Respiration uses another electron acceptor (nitrogen)
Smaller reduction potential, less proton motive force across membranes and less energy released per molocule oxidised. (Alternative is fermentation)

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42
Q

What is a facultative anaerobe?

A

Tolerates oxygen

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43
Q

What is a capnophile?

A

Prefer CO2 conditions

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44
Q

What is a selective media?

A

a culture medium containing ingredients that inhibit growth of contaminants or microorganisms other than that desired.

45
Q

What is a differential media?

A

a medium that can allow different types of organism to be distinguished by their different forms of growth.

46
Q

What type of medium is Mannitol salt agar and what organism is it used to identify?

A

Selective

Staphylococci

47
Q

What type of medium is Salmonella Shingella and what organism is it used to identify?

A

Selective

Bile salts and inhibits coliforms eg ecoli

48
Q

What is haemolysis used to identify?

A

Streptococci

49
Q

What is alpha, beta and gamma haemolysis?

A 
Alpha = blaching of erythrocytes 
Beta = Bacteria digest erythrocytes around them = group A strep
Gamma = no haemolysis
50
Q

What type of medium is MacConkay agar and what organism is it used to identify?

A

Differential

Identification of enetrobacteriaceae

51
Q

What type of medium is Eosin and methylene blue and what organism is it used to identify?

A

Differential

Identification of lactose fermenters like E coli

52
Q

What is the linnaean classification?

A 
King Philip came over from great spain
Kingdom
Phylum
Class
Order
Family
Genus
Species
53
Q

What biochemical tests/markers can hep identify bacteria?

A

Metabolic profiling
Exoenzyme production
Now all automater

54
Q

What is a serological test and what are the advantages?

A

Agglutination reaction of IgM antibody with a specific antigen on bacteria
+ Rapid detection 24 hours, can identify different stereotypes of bacteria, works well if you know what you’re looking for

55
Q

What is genome sequencing?

A

Sequence DNA targetusing PCR and primers and compare with many organisms that have already been sequenced

56
Q

What is MALDI-TOF and what is it used for?

A

Used for identifying peptides an their patterns of arrangement. Works like a mass spectrometer.
Very precise identification of bacteria and cost effective

57
Q

What is Multi locus sequence typing used for?

A

Checking resistance of an organism => targeted prescribing

58
Q

What are the 8 steps to pathogenesis of bacteria?

A

1) Reservoir of pathogen
2) Enter host
3) Colonise/invade host
4) Overcome host defences
5) Multiply complete life cycle
6) Damage the host
7) Exit the host
8) Released and spread

59
Q

What is an endogenous pathogen?

A

Pathogens which live in the body normally but become pathogenic

60
Q

What is virulence?

A

The capacity of a microbe to cause damage to the host. LD50 is the level at which 50% of infected organisms die

61
Q

What is a microbiome?

A

Natural microorganisms that live within the body

62
Q

What is an exogeneous organism?

A

Not normal flora but can be beneficial and give protection from other microorganisms.
Can also be pathogenic

63
Q

What is a pathogen?

A

A disease causing organism

64
Q

What is a commensal?

A

An organism that is part of the normal flora. Often mutualistic symbiosis and an endogeneous organism

65
Q

What is a contaminant?

A

Organism in a culture by accident

66
Q

What is an opportunistic pathogen?

A

Organism that causes infection when opportunity/ change in natural immunity arises

67
Q

Give 2 examples of common fungal pathogens?

A

Candida (budding yeast)
Linked to prescriptions of antibiotics because more nutrients are available and inhaler use as steroids suppress the immune system
Aspergillus (mould)
Infection in the immunocomprimised

68
Q

Give 3 examples of protozoa?

A

Malaria, toxoplasma, Leishmaniasis

GI infection: cryptosporidiosis

69
Q

Gram positive or gram negative: Neisseria?

A

-

70
Q

Gram positive or gram negative: Escherichia?

A

-

71
Q

Gram positive or gram negative: Streptococcus?

A

+

72
Q

Gram positive or gram negative: Klebsiella?

A

-

73
Q

Gram positive or gram negative: Enterobacter?

A

-

74
Q

Gram positive or gram negative: salmonella?

A

-

75
Q

Gram positive or gram negative: Staphylococcus?

A

+

76
Q

Gram positive or gram negative: Enterococcus?

A

+

77
Q

Gram positive or gram negative: Shingella?

A

-

78
Q

Gram positive or gram negative: Haemophylous?

A

-

79
Q

Gram positive or gram negative: Clostridium?

A

+

80
Q

Gram positive or gram negative: Fusobacterium?

A

+

81
Q

Gram positive bacteria produce endo/exotoxin?

A

Exotoxin

82
Q

Gram negative bacteria produce endo/exotoxin?

A

Endotoxin

83
Q

What is the most common cause of bacterial meningitis?

A

Neisseria Meningitidis

Gram negative cocci (aerobic diplococci)

84
Q

What causes gonorrhoea?

A

Neisseria Gonorrhoea
Gram negative cocci (aerobic diplococci)
Becoming resistant to azithromycin

85
Q

What is a colliform?

A

Species of gram negative bacilli that look like E coli on a gram film

86
Q

What are the characteristics of coliforms?

A

Grow best aerobically but can grow anaerobically
Part of normal bowel flora
Differentiated from each other by biochemical reactions and the antigenic structure of the cell wall.

87
Q

Where is a O antigen, K antigen and a H antigen found on a coliform?

A

O on the cell wall
H on flagella
K on the capsule

88
Q

Gram positive or gram negative: Proteus?

A

-

89
Q

When is endotoxin released?

A

Released from the cell wall when gram negative bacteria die

90
Q

What is the first line antibiotic for coliforms?

A

Gentamycin

91
Q

What is SIRS?

A

Systemic inflamatory response syndrome (Endotoxin shock)

92
Q

What happens in SIRS?

A

Endotoxin, LPS, Peptidoglycan bind to receptors on macrophages. Endotoxins can also bind to T cells
=> Release of inflamatory cytokines and an immune response

93
Q

Is a fever considered benifical in infection?

A

Yes as the higher temperature slows bacterial growth

94
Q

What is sepsis?

A

Step up from SIRS.

1) Small blood vesels become leaky => oedema and reduced blood volume
2) Lower blood volume => lower BP and increased work of the heart to perfuse tissues
3) Poor perfusion means blood supply to less essential organs is shut down
4) COagulation cascade is activated => clotting in small vessels uses all the clotting factors => increased risk of haemorrhage

95
Q

Which strep species show alpha haemolysis?

A

S. pneumoniae and S. viridans

96
Q

Which strep species show beta haemolysis?

A

Strep group A, B, C, F, G

97
Q

Which strep species show gamma haemolysis?

A

Strep group B and enterococci

98
Q

What is VRE?

A

Vancomycin resistant Enterococci.

Common outbreaks in hospitals

99
Q

Where is enterococci usually found?

A

Part of normal bowel flora and a common cause of UTI

100
Q

What infections does S aureus usually cause?

A

Bone and joint infections
Skin and wound infections
Food poisoning

101
Q

What infections are associated with staph epidemidis?

A

Infections associated with external devices eg heart valves and catheters.
Lives on skin and mucus membranes

102
Q

Is staph aureus a aerobic bacteria?

A

Yes

103
Q

What is MRSA and which patients are more likely to get it?

A

Methacillin resistant staph aureus
Elderly, immunocomprimised, burns and surgical patients
Dialasis and IV lines are risk factors

104
Q

What type of organism is clostridium?

A

Gram positive ANAEROBIC organism which produces spores which can survive for months and exotoxins which cause severe tissue dammage

105
Q

When does C diff perliferate?

A

In the absence of normal gut flora

106
Q

Clostridium difficile causes what?

A

Chronic diarrhoea in elderly

107
Q

Clostridium perfringes causes what?

A

Gangrene

108
Q

Clostridium tetani causes what?

A

Tenanus

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