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MEDI 203 - Body Defence > Bacterial Infection & Antimicrobial Resistance > Flashcards

Bacterial Infection & Antimicrobial Resistance Flashcards

1
Q

What is the first barrier of host defence?

A

The skin

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2
Q

What does the number and variety of microorganisms depend on?

A

Moisture
pH
Temperature
Salinity
Chemical wastes (urea and fatty acids)
Presence of other microbes

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3
Q

What are the three regions where different skin microbiota live?

A

Sebaceous sites
Moist sites
Dry sites

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4
Q

What are the normal skin microbiota?

A

Staphylococcus
Micrococcus
Diphtheroids
Malassezia furfur

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5
Q

Which is the most common skin microbiota?

A

Staphylococcus

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6
Q

What is the most common skin microbiota infection?

A

Acne Vulgaris

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7
Q

Is acne chronic or acute inflammation?

A

Chronic inflammation

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8
Q

What causes acne?

A

Propionibacterium acnes

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9
Q

What are the characteristics required for bacterial pathogenesis?

A

Route of entry
Adhesion
Colonisation & Invasion
Virulence factors
Survival

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10
Q

How is the skin abscess formation caused by staphylococcus aureus?

A

Bacterial entry & Adherence
Bacterial proliferation & PMNs influx
Abscess & pus formation

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11
Q

What is the infection triangle for disease?

A

Susceptible host
Virulent Pathogen
Favorable Environment

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12
Q

What is the infection triangle for less disease?

A

Susceptible host
Virulent Pathogen
Unfavourable Environment

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13
Q

What are examples of a susceptible host?

A

Burned skin or no defence

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14
Q

What are examples of virulent pathogens?

A

S. aureus
Virulence factors

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15
Q

What are examples of favourable environment?

A

Damaged tissue
Abundant nutrients for pathogen
Exposed wound
Lack of preventive measures

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16
Q

What is the bacterial growth cycle?

A

Bacteria divide by binary fission
Bacterial growth byproducts due to fermentation are acid, gas & various metabolites

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17
Q

What are the bacteria doubling time range?

A

Between 20 minutes (fast-growing) to more than 24 hours (slow growing bacteria)

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18
Q

When do bacteria start growing more rapidly?

A

When they establish their niche

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19
Q

What are the different stages of the bacterial growth cycle?

A

Lag phase
Log phase
Decline growth phase
Endogenous respiration phase

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20
Q

What happens in the lag phase?

A

No cell division occurs while bacteria adapt to their new environment

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21
Q

In which phase is there an exponential growth of the population, human disease symptoms usually develop?

A

The log phase

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22
Q

What is the stationary phase?

A

Reproductive and death rates equalize

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23
Q

What happens during the decline phase?

A

Accumulation of waste products and scarcity of resources causes population to die

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24
Q

What are the functions of the bacterial capsule (glycocalyx)?

A

Adhering layer of polysaccharides
Protects cells from the environment and allows them to attach to surfaces
Inhibits phagocytosis by immune cells

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25
Q

What is a capsule?

A

A thick layer of glycocalyx

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26
Q

What is a slime layer?

A

A diffuse layer of polysaccharides

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27
Q

What are pili?

A

Protein fibers extending from the surface of many bacteria that are used for attachment

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28
Q

What is the function of conjugation pili?

A

Transfer genetic material between cells

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29
Q

What is the function of the flagella?

A

Provide motility

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30
Q

What does a prokaryotic flagella contain?

A

Helical filament, a hook and a basal body

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31
Q

What is the bacterial cell wall?

A

A tough and protective external shell

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32
Q

What is the function of the cell wall?

A

Protects the cell from injury

Maintains the cell shape and water balance

Providing attachment sites

Countering effects of osmotic pressure

Essential for cell division

Antigenic determinants

Resistance of antibiotics

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33
Q

What does a ruptured bacterial cell wall mean?

A

Cell death

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34
Q

What is the structure of gram-negative bacteria cell wall?

A

Lipopolysaccharides also called endotoxins

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35
Q

What is the structure of gram-positive bacteria cell wall?

A

Thick peptidoglycan layer

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36
Q

What part of the bacteria represents a selectively permeable barrier?

A

The cell membrane

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37
Q

Which part of the bilayer form a permeability barrier? Why?

A

The hydrophobic fatty acid chain because they are negatively charged

38
Q

What are the functions of the membrane proteins?

A

Cell wall synthesis
Energy metabolism
DNA replication
Sensation of stimuli
Molecule transport, and active transport

39
Q

Where do ribosomes exist?

A

In cell cytoplasm

40
Q

What is the function of ribosomes?

A

Protein synthesis

41
Q

How is bacterial DNA organised?

A

With the nucleoid

42
Q

How does the DNA of chromosomes usually exist as?

A

Single, circular chromosomes

43
Q

What is the structure of DNA with a nucleoid?

A

Highly compacted

44
Q

What do plasmids carry?

A

Nonessential but often useful information

45
Q

What are the bacterial cell shapes?

A

Cocci, bacilli, coco bacilli, spiral

46
Q

What kind of tests help identify the genus and the species of bacteria?

A

Colony morphology, biochemical tests and serological tests

47
Q

How do antibiotics kill bacteria?

A

Cell wall (peptidoglycan synthesis)
Protein synthesis
Membrane integrity
Nucleic acid synthesis
Metabolic pathways

48
Q

Which components of the cells are affected by antibacterials?

A

Membrane
Ribosomes
Metabolic pathways

49
Q

Which antibiotics affect the cell wall?

A

β-lactams:
Penicilins
Cephalosporins
Carbapenems
Monobactams
Bacitracin
Glycopeptides

50
Q

Which antibiotics affect the protein synthesis?

A

30s inhibitors:
Aminoglycosides
Tetracyclines
Tigecycline

50s inhibitors:
Chloramphenicol
Clindamycin
Linezolid
Macrolides
Streptogramins

51
Q

Which antibiotics affect the membrane integrity?

A

Polymixin B
Daptomycin

52
Q

Which antibiotics affect the nucleic acid synthesis?

A

Fluroquinolones
Metronidazole
Rifamycins

53
Q

Which antibiotics affect the metabolic pathways (folate)?

A

Sulfonamides
Trimethoprim

54
Q

What are the antimicrobial resistance mechanisms?

A

Efflux pump
Blocked penetration
Inactivation of enzymes
Target modification

55
Q

Which antibiotics are affected by efflux pumps in antimicrobial resistance?

A

Fluoroquinolones
Aminoglycosides
Tetracyclines
β-lactams
Macrolides

56
Q

Which antibacterial are affected by blocked penetration?

A

β-lactams
tetracyclines
fluroquinolones

57
Q

Which antibacterials are affected by the inactivation of enzymes?

A

β-lactams
aminoglycosides
macrolides
rifamycins

58
Q

What do target modifications (mutation) affect?

A

fluoroquinolones
rifamycins
vancomycin
β-lactams
macrolides
aminoglycosides

59
Q

Which organelles affected by target modifications?

A

Ribosomes & DNA

60
Q

What is DNA gyrase?

A

Essential bacteria enzyme responsible for replication

61
Q

How do fluoroquinolones affect the DNA gyrase?

A

They attach to it, blocking bacteria DNA replication leading to cell death.

62
Q

How does antibiotic resistance occur?

A

Population of bacteria
Bacteria divide, and one cell undergoes a mutation
Cell with gene conferring resistance to antibiotic
Only resistance cell survives
Bacterium divides many times

63
Q

What are the mechanisms of antibiotic resistance?

A

Intrinsic or acquired

64
Q

Where does acquired resistance come from?

A

Genetic methods –> chromosomal methods or extra chromosomal methods

65
Q

What are the chromosomal methods of antibiotic resistance?

A

Mutations

66
Q

What are the extra chromosomal methods of antibiotic resistance?

A

Plasmids

67
Q

How does antibiotic resistance happen from one bacteria to the rest?

A

Lots of germs, and only a few drug-resistant
Antibiotics kill bacteria causing the illness, as well as good bacteria protecting the body from infection.
The drug-resistant bacteria are allowed to grow and take over.
Some bacteria give their drug-resistance to other bacteria, causing more problems.

68
Q

What kind of bacteria does an antibiotic kill?

A

Both bacteria that cause the disease and good bacteria that protect the organism

69
Q

What are the mechanisms of antibiotic antibiotic resistance gene transfer?

A

Transformation
Transduction
Conjugation

70
Q

What is antibiotic resistance gene transfer transformation?

A

Donor cell releases DNA including antibiotic-resistant genes to the recipient cell

71
Q

What is the antibiotic resistance gene transfer transduction?

A

Phage-infected donor cell releases phage onto the recipient cell

72
Q

What is a phage?

A

Small virus that affects bacteria

73
Q

What is the antibiotic resistance gene transfer conjugation?

A

Transposon from the donor cell is transported to the recipient cell.

74
Q

What are the three fundamental mechanisms of antimicrobial resistance?

A

Enzymatic degradation
Alteration of bacterial proteins
Changes membrane permeability to antibiotics

75
Q

In which ways do bacteria produce enzymes that inactivate the antibiotics?

A

Inactivation of β-lactams
Inactivation of chloramphenicol
Inactivation of aminoglycosides

76
Q

Which bacteria inactivate the β-lactams?

A

S. aureus, N. gonorrhoea, H. influenza

77
Q

How do bacteria inactivate the β-lactams?

A

They produce β-lactamase which cleaves β-lactam ring

78
Q

How is chloramphenicol inactivated?

A

By chloramphenicol acetyltransferase

79
Q

Which kind of bacteria have a higher resistance to chloramphenicol and why?

A

Gram -ive because the enzyme chloramphenicol acetyltransferase is present

80
Q

How are aminoglycosides inactivated?

A

Inactivated by acetyl, phospho, and adenylyl transferases which are present in both kinds of bacteria

81
Q
A
82
Q

Which antibiotic is altered in such a way that it binds to 50s r-RNA and prevents movement along m-RNA?

A

Erythromycin

83
Q

How does altered tetracycline interfere with antibiotic targets?

A

Tetracycline interferes with the t-RNA anticodon reading of m-RNA

84
Q

Which antibiotic is altered in such a way where it is responsible for the change of shape of 30s r-RNA and causes m-RNA to be read incorrectly?

A

Streptomycin

85
Q

What is the function of the efflux pump?

A

It recognises the antibiotic and kicks it out.

86
Q

In the disc diffusion method what is measured?

A

Zone of inhibition in mm

87
Q

How is bacterial sensitivity categorised in the disc diffusion method?

A

Sensitive, Intermediate and Resistant
It depends on the diameter of the zone of inhibition, the greater the zone the more effective the antibiotic

88
Q

What does the e-testing method determine?

A

The minimum inhibitory concentration in μg/ml

89
Q

What does a low MIC indicate?

A

The antibiotic is working and a lower dose is required to reach the target effect.

90
Q

Which are the ESKAPE pathogens?

A

E: enterococci
S: staphylococcus aureus
K: klebsiella
A: acinetobacter
P: pseudomonas aeruginosa
E:enterobacter

91
Q

What are ESAKPE pathogens?

A

They are the pathogens that carry and spread the antibiotic resistance

92
Q

What might cause antibiotic resistance?

A

Over-prescription
Misuse of antibiotics
Antibiotics used in agriculture
Poor infection control
Poor hygiene
Lack of rapid lab tests

MEDI 203 - Body Defence (6 decks)

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