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

Bacterial Infection & Antimicrobial Resistance Flashcards

(92 cards)

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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
What is a capsule?
A thick layer of glycocalyx
26
What is a slime layer?
A diffuse layer of polysaccharides
27
What are pili?
Protein fibers extending from the surface of many bacteria that are used for attachment
28
What is the function of conjugation pili?
Transfer genetic material between cells
29
What is the function of the flagella?
Provide motility
30
What does a prokaryotic flagella contain?
Helical filament, a hook and a basal body
31
What is the bacterial cell wall?
A tough and protective external shell
32
What is the function of the cell wall?
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
33
What does a ruptured bacterial cell wall mean?
Cell death
34
What is the structure of gram-negative bacteria cell wall?
Lipopolysaccharides also called endotoxins
35
What is the structure of gram-positive bacteria cell wall?
Thick peptidoglycan layer
36
What part of the bacteria represents a selectively permeable barrier?
The cell membrane
37
Which part of the bilayer form a permeability barrier? Why?
The hydrophobic fatty acid chain because they are negatively charged
38
What are the functions of the membrane proteins?
Cell wall synthesis Energy metabolism DNA replication Sensation of stimuli Molecule transport, and active transport
39
Where do ribosomes exist?
In cell cytoplasm
40
What is the function of ribosomes?
Protein synthesis
41
How is bacterial DNA organised?
With the nucleoid
42
How does the DNA of chromosomes usually exist as?
Single, circular chromosomes
43
What is the structure of DNA with a nucleoid?
Highly compacted
44
What do plasmids carry?
Nonessential but often useful information
45
What are the bacterial cell shapes?
Cocci, bacilli, coco bacilli, spiral
46
What kind of tests help identify the genus and the species of bacteria?
Colony morphology, biochemical tests and serological tests
47
How do antibiotics kill bacteria?
Cell wall (peptidoglycan synthesis) Protein synthesis Membrane integrity Nucleic acid synthesis Metabolic pathways
48
Which components of the cells are affected by antibacterials?
Membrane Ribosomes Metabolic pathways
49
Which antibiotics affect the cell wall?
β-lactams: Penicilins Cephalosporins Carbapenems Monobactams Bacitracin Glycopeptides
50
Which antibiotics affect the protein synthesis?
30s inhibitors: Aminoglycosides Tetracyclines Tigecycline 50s inhibitors: Chloramphenicol Clindamycin Linezolid Macrolides Streptogramins
51
Which antibiotics affect the membrane integrity?
Polymixin B Daptomycin
52
Which antibiotics affect the nucleic acid synthesis?
Fluroquinolones Metronidazole Rifamycins
53
Which antibiotics affect the metabolic pathways (folate)?
Sulfonamides Trimethoprim
54
What are the antimicrobial resistance mechanisms?
Efflux pump Blocked penetration Inactivation of enzymes Target modification
55
Which antibiotics are affected by efflux pumps in antimicrobial resistance?
Fluoroquinolones Aminoglycosides Tetracyclines β-lactams Macrolides
56
Which antibacterial are affected by blocked penetration?
β-lactams tetracyclines fluroquinolones
57
Which antibacterials are affected by the inactivation of enzymes?
β-lactams aminoglycosides macrolides rifamycins
58
What do target modifications (mutation) affect?
fluoroquinolones rifamycins vancomycin β-lactams macrolides aminoglycosides
59
Which organelles affected by target modifications?
Ribosomes & DNA
60
What is DNA gyrase?
Essential bacteria enzyme responsible for replication
61
How do fluoroquinolones affect the DNA gyrase?
They attach to it, blocking bacteria DNA replication leading to cell death.
62
How does antibiotic resistance occur?
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
What are the mechanisms of antibiotic resistance?
Intrinsic or acquired
64
Where does acquired resistance come from?
Genetic methods --> chromosomal methods or extra chromosomal methods
65
What are the chromosomal methods of antibiotic resistance?
Mutations
66
What are the extra chromosomal methods of antibiotic resistance?
Plasmids
67
How does antibiotic resistance happen from one bacteria to the rest?
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
What kind of bacteria does an antibiotic kill?
Both bacteria that cause the disease and good bacteria that protect the organism
69
What are the mechanisms of antibiotic antibiotic resistance gene transfer?
Transformation Transduction Conjugation
70
What is antibiotic resistance gene transfer transformation?
Donor cell releases DNA including antibiotic-resistant genes to the recipient cell
71
What is the antibiotic resistance gene transfer transduction?
Phage-infected donor cell releases phage onto the recipient cell
72
What is a phage?
Small virus that affects bacteria
73
What is the antibiotic resistance gene transfer conjugation?
Transposon from the donor cell is transported to the recipient cell.
74
What are the three fundamental mechanisms of antimicrobial resistance?
Enzymatic degradation Alteration of bacterial proteins Changes membrane permeability to antibiotics
75
In which ways do bacteria produce enzymes that inactivate the antibiotics?
Inactivation of β-lactams Inactivation of chloramphenicol Inactivation of aminoglycosides
76
Which bacteria inactivate the β-lactams?
S. aureus, N. gonorrhoea, H. influenza
77
How do bacteria inactivate the β-lactams?
They produce β-lactamase which cleaves β-lactam ring
78
How is chloramphenicol inactivated?
By chloramphenicol acetyltransferase
79
Which kind of bacteria have a higher resistance to chloramphenicol and why?
Gram -ive because the enzyme chloramphenicol acetyltransferase is present
80
How are aminoglycosides inactivated?
Inactivated by acetyl, phospho, and adenylyl transferases which are present in both kinds of bacteria
81
82
Which antibiotic is altered in such a way that it binds to 50s r-RNA and prevents movement along m-RNA?
Erythromycin
83
How does altered tetracycline interfere with antibiotic targets?
Tetracycline interferes with the t-RNA anticodon reading of m-RNA
84
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?
Streptomycin
85
What is the function of the efflux pump?
It recognises the antibiotic and kicks it out.
86
In the disc diffusion method what is measured?
Zone of inhibition in mm
87
How is bacterial sensitivity categorised in the disc diffusion method?
Sensitive, Intermediate and Resistant It depends on the diameter of the zone of inhibition, the greater the zone the more effective the antibiotic
88
What does the e-testing method determine?
The minimum inhibitory concentration in μg/ml
89
What does a low MIC indicate?
The antibiotic is working and a lower dose is required to reach the target effect.
90
Which are the ESKAPE pathogens?
E: enterococci S: staphylococcus aureus K: klebsiella A: acinetobacter P: pseudomonas aeruginosa E:enterobacter
91
What are ESAKPE pathogens?
They are the pathogens that carry and spread the antibiotic resistance
92
What might cause antibiotic resistance?
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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