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Microbiology 1 > ANTIBIOTICS > Flashcards

ANTIBIOTICS Flashcards

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1
Q

What are important considerations when prescribing antimicrobial therapy

A
  1. Obtaining an accurate diagnosis of infection
  2. Understanding drug characteristics that are perculiar to antimicrobial agents
  3. Understanding the difference between empiric and definitive therapy
  4. Cost effective oral agents for the shortest duration necessary
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2
Q

What are antibiotics

A

Are substances obtained and purified from other microbial organisms

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3
Q

What is the difference between bacteriostatic and bactericidal

A

Bactericidal antibiotics kill bacteria.
Bacteriostatic antibiotics inhibit bacterial growth and reproduction

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4
Q

Difference between broad spectrum and wide spectrum antibiotics

A

Narrow-Spectrum Antibiotics:
Purpose: These antibiotics target a specific range of bacteria.

Broad-Spectrum Antibiotics:
Purpose: Formulated to combat a wide range of bacterial infections.

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5
Q

Mention 4 examples of general bacteriostatic

A

Trimethoprim
Tetracyclines
Linezolid
Erythromycin

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6
Q

Mention 4 examples of bactericidal antibiotics

A

Vancomycin
Telavancin
Metronidazole
Teicoplanin

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7
Q

Classify antibiotics based on their mechanism of action

A

1.Target bacterial cell wall biosynthesis
2. Target ribosomes
3. DNA replication

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8
Q

Mention the antibiotics that inhibits cell wall synthesis

A
  1. Penicillins
  2. Cephalosporins
  3. Glycopeptides
  4. Vancomycin
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9
Q

What is the use of penicillin antibiotic group

A

An antibiotic that that inhibits cell wall synthesis

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10
Q

General characteristics of penicillins

A
  1. Safe, with very few side effects in pregnancy
  2. Range from narrow to broad spectrum
  3. Excreted rapidly via kidneys
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11
Q

What are some drawbacks with penicillins

A

Hypersensitivity
Frequent dosing ( 4-6 daily)

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12
Q

Explain the 3 forms of penicillin

A
  1. Benzylpenicilin contains penicillin G: administered intravenously against gram positive bacteria
  2. Phenoxymethyl penicillin contains penicillin V; administered orally gram negative organism
  3. Long acting penicillin administer intramuscular mainly used for clostridium, strptococcus and neisseira
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13
Q

What is co-amoxiclav

A

Is a combination of amoxicillin + clavulanic acid ( beta- lactamase inhibitor) and combination extends the range of bacteria that can be treated

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14
Q

A combination of antibiotic + b lactamase inhibitor

A

Piperacilin tazobactam

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15
Q

What will piperacilin tazobactam treat

A

Gram negative bacterial infections including paeudomonas infection

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16
Q

Explain the mechanism of cephalosporins

A

Inhibits cell wall synthesis by preventing cross linking of peptidoglycan

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17
Q

Advantages of cephalosporins

A
  1. They are broad spectrum
    (with significant effects on the normal bowel flora)
  2. Few side effects
  3. Safe
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18
Q

Disadvantages of cephalosporins

A
  1. Affects the normal bowel flora
  2. It kills normal gut bacteria + and allows overgrowth of C. Difficile, causing gastroenteritis
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19
Q

Explain the mechanism of Glycopeptides

A
  1. Are cell wall active antibiotics that work differently from penicillins
  2. Binds to end of growing pentapeptide chain during peptidoglycan synthesis, preventing cross-linking and weakening the bacteria cell wall
  3. It is administered intravenously
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20
Q

What is the mechanism of bacterial ribosome antibiotics

A

They inhibit protein synthesis by attaching to bacteria ribosomes. Inhibits growth but does not kill the bacteria, the bacteria are killed by wbc

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21
Q

What are macrolides bacteria

A

They are lipophilic and pass through cell membrane easily and are useful in treating infections where bacteria get into host cells in order to avoid immune system attack

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22
Q

What are examples of macrolides

A

Erythromycin
Clarythromicin
Azithromycin

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23
Q

Mechanism of aminoglycocides

A

They bind to ribosomes to inhibit protein synthesis but are bactericidal

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24
Q

When do aminoglycocides get used

A

Mainly against gram negative aerobic organisms and in hospitals for treating life threatening gram negative infections

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25
Q

Disadvantages of aminoglycocides (gentamicin)

A

Lower margin between giving enough antibiotic to treat infection and overdosing so blood levels requres frequent monitoring

Can cause damage to kidneys and 8th cranial merve and deafness

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26
Q

What are tetracycline

A

Attaches to ribosomes and are bacterialstatic

27
Q

What are the examples of tetracycline

A
  1. Doxycycline
  2. Clindamycin
  3. Chloramphenicol
28
Q

When is doxycycline used

A

Used for treating infections caused by bacteria that do not have a proper cell wall and some chest or skin infections to those who are penicillin allergic

29
Q

When is chloramphenicol used

A

To treat eye infections

30
Q

Mention examples of bacterial DNA antibiotics

A
  1. Metronidazole
  2. Trimethoprim/sulfamethoxazole
  3. Fluoroquinolones
31
Q

Mechanism of metronidazole

A

Acts by causing strand breakage of bacterial DNA.
Used for infection caused by true anaerobes and some protozoa. ( sindle celled parasits )

32
Q

When is metronidazole used

A

For clostridium and bacteroides

33
Q

What is the synthesis of trimethoprim

A

Inhibits bacterial folic acid synthesis. Bith + and -

34
Q

What is the mechanism of fluoroquinolones

A

Acts by interacting with topoisomerases- enzymes responsible for supercoiling and uncoiling of bacterial DNA. This results in the bacteria being unable to replicate. Only administered in complicated urinary tracy infections

35
Q

What are advantages of combinations of antimicrobial drugs

A

Synergism: the combination is more effective than either drug used separately

36
Q

What are disadvantages of combination of atimicrobial drugs

A

Bacteriostatic drugs may interfere with bacterialcidal

37
Q

What are the general side effects of antibiotics

A
  1. Nausea and diarrhea
  2. Failure of oral contraception
  3. Overgrowth of toxic C. Difficile
38
Q

What are specific side effects of antibiotics

A
  1. Aminoglycosides- gentamicin damages kidneys and causes deafness and dizziness
  2. Glycopeptides- vancomycin damages kidneys
  3. Tetracycline- Doxycyline permanent staining of teeth in children < 12
  4. Quinolones- ciprofloxacan weakens tendons, joint damage in children and seizures
39
Q

What are the side effects of penicillin

A

Type 1 hypersensitivity which includes itchy rash, difficult breathing, swelling of the mouth, low blood pressure

40
Q

Define antimicrobial resistance

A

Is the ability of a microorganism to stop an antimicrobial (antibiotics) from working against it

41
Q

Disadvantages of antimicrobial resistance (AMR)

A
  1. The cost of health care for patients with resistant infections is higher than care for patients with non resistant infections due to longer duration of illness, additional tests and use of more expensive drugs
  2. Without effective antibiotics the success of major surgery and cancer chemotherapy would be compromised
42
Q

What are the mechanisms by which a bacteria acquire resistance

A
  1. A change in bacterial DNA can change the gene product that is the target of the antibiotic e.g penicillin
  2. Enzymes inactivating the antibiotics. E.g b-lactam antibiotics can be inactivated by b lactamases
  3. Active transport of the antibiotic out of the bacteria cell (efflux pumps). Efflux pumps are channels that actively export antibiotics out of the bacteria cell waa
  4. Decreased permeability of the bacteria cell wall to the antibiotic
43
Q

What are the factors that promote antimacrobial resistance

A
  1. Exposure to sub- optimal levels of antimicrobial
  2. Exposure to microbes carrying resistance genes
  3. Inappropriate antimicrobial use
44
Q

What examples of inappropriate antimicrobial use

A
  1. Prescription not taken correctly
  2. Antibiotics used to treat viral infections
  3. Antibiotics sold without medical supervision
  4. Lack of quality control in manufacture or outdated antimicrobial
45
Q

What are the consequences of antimicrobial resistance

A
  1. Development of infections resistant to available antibiotics
  2. Increased cost of treatment
  3. Increased mortality
  4. Prolonged hospital stays for individuals with drug resistant infections
46
Q

What is the most hospital acquired pathogen resistant to several antibiotics

A

MRSA (methicillin resistant staphylococcus aureus)

47
Q

What are the propasals to combat antimicrobial resistance

A

I. Speed development of new antibiotics
2. Track resistant data worldwide
3. Use more narrow spectrum antibiotics

48
Q

Define antimicrobial susceptible testing

A

Is a test used to detect antimicrobial resistance

49
Q

What are the names of the methods used to antimicrobial susceptibility testing

A
  1. Agar dilution
  2. Broth dilution
  3. Disk diffusion assay
50
Q

Explain the broth method of antibiotics sensitivity test

A

The broth dilution method involves subjecting the isolate to a series of concentrations of antimicrobial agents in a broth environment .
Microdilution and macrodilution is envolved.
For both of these broth dilution methods the lowest concentration at which the isolate is completely inhibited is recorded as the minimal inhibitory concentration (MIC).

51
Q

What is the broth dilution method in antibiotic sensitivity testing?

A

The broth dilution method involves subjecting the bacterial isolate to a series of concentrations of antimicrobial agents in a broth environment.

52
Q

How is minimal inhibitory concentration (MIC) determined in broth dilution methods?

A

MIC is the minimum concentration of the antibiotic that inhibits visible bacterial growth. It’s recorded as MIC when the positive control shows growth, and the negative control shows no growth.

53
Q

What volume is used for microdilution testing?

A

Microdilution testing uses about 0.05 to 0.1 ml total broth volume and can be conveniently performed in a microtiter format.

54
Q

Describe the agar dilution method similar to both dilution methods.

A
  • The agar dilution method follows the same principle as the broth dilution methods. It aims to establish the lowest concentration of serially diluted antibiotics at which bacterial growth is still inhibited.
55
Q

What is the purpose of the disk diffusion method in microbiology?

A

The disk diffusion method is used to determine the susceptibility or resistance of bacterial isolates to specific antibiotics.

56
Q

How is minimal inhibitory concentration (MIC) determined in broth dilution methods?

A

MIC is the minimum concentration of the antibiotic that inhibits visible bacterial growth. It’s recorded as MIC when the positive control shows growth, and the negative control shows no growth.

57
Q

What volume is used for microdilution testing?

A

Microdilution testing uses about 0.05 to 0.1 ml total broth volume and can be conveniently performed in a microtiter format.

58
Q

What does the “zone of inhibition” indicate in the disk diffusion method?

A

The zone of inhibition represents the area around each antibiotic disk where bacterial growth is inhibited. It indicates the minimum effective concentration of the antibiotic against the test isolate.

59
Q

How are commercially prepared disks utilized in this method?

A

Commercially prepared disks come pre-impregnated with a standard concentration of specific antibiotics. These disks are placed evenly on the agar surface.

60
Q

Which growth medium is commonly used in the disk diffusion method?

A

Mueller-Hinton agar is the preferred growth medium for the disk diffusion method.

61
Q

What is the purpose of the disk diffusion method in microbiology?

A

The disk diffusion method is used to determine the susceptibility or resistance of bacterial isolates to specific antibiotics.

62
Q

Explain the disk effusion method

A

A growth medium usually mueller-hinton agar is evenly seeded throughout the plate with isolate of interest that has been diluted at a standard concentration 1-2 x 180 colony forming units per ml
The test antibiotic immediately begins to diffuse outward from the disk,creating a gradient of antibiotic concentration in the agar such that the highest concentration is found close to the disk with decreasing concentrations

63
Q

Eplain the mechanism of E. test

A

Is a commercially available test that utilizes a plastic test strip impregnated with a gradually decreasing concentration.

64
Q

What are the advantages of e test

A

Provides a covenient quantitative test of antibiotic resistant of a clinical isolate

Microbiology 1 (27 decks)

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