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BACTERIOLOGY > Antimicrobial agents > Flashcards

Antimicrobial agents Flashcards

Mechanism of action and resistance

1
Q

These agents cause cell lysis, thus killing bacteria. These agents “attack” microbes by affecting the cell wall, lipids, enzymes, or protein synthesis within the cell – sometimes even completing a combination of these mechanisms

A

Bactericidal agents

  • By disrupting the cell wall structure of existing cells and inhibiting the formation of new cells, bactericidal substances cause bacterial cells to die off, therefore decreasing the amount found in the individual affected.
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2
Q

These agents cause cell lysis, thus killing bacteria. These agents “attack” microbes by affecting the cell wall, lipids, enzymes, or protein synthesis within the cell – sometimes even completing a combination of these mechanisms

A

Bactericidal agents

  • By disrupting the cell wall structure of existing cells and inhibiting the formation of new cells, bactericidal substances cause bacterial cells to die off, therefore decreasing the amount found in the individual affected.
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3
Q

These agents inhibit the growth and multiplications of bacterial cells, rather than directly killing them.

A

Bacteriostatic agents.

-they can achieve this by obstructing the metabolic mechanisms of the bacterial cell, in most cases targeting the protein synthesis. While doing this does not cause outright cell death, it does effectively inhibit further growth and DNA replication of the bacterial cells.

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4
Q

Examples of bactericidal agents

A
  • Penicillin, cephalosporins, and vancomycin
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5
Q

Examples of bacteriostatic agents

A
  • Tetracycline, sulfonamides, and erythromycin
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6
Q

Antibacterial agents can be categorized into two spectrum: _______ and ________

A

-Narrow and Broad spectrum

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7
Q

These refer to antibiotics with limited spectrum and target only few types of bacteria

e.g: Penicillin G which is effective against gram negative bacteria only

A

-Narrow spectrum antibiotics

also Vancomycin since it is a very large molecule it cannot penetrate the outer membrane of gram-positive bacteria so it is also effective only in gram negative bacteria

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8
Q

These antibiotics have an antimicrobial spectrum which includes some gram-positive and some gram-negative organisms, as well as certain rickettsiae, larger viruses, protozoa, and pleuropneumonia-like organisms. Antibiotics with a wide range effect

A

Broad spectrum antibiotics

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9
Q

True or false: Narrow-spectrum antibiotics are more likely to lead to bacteria that resist drugs. This leads to infections that last longer and cost more to treat.

A

False.

-it should be broad spectrum antibiotics

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10
Q

True or false: Broad spectrum antibiotics may inhibit and destroy normal flora — a new infection may appear (superinfection) as a result of antibiotic treatment

A

True

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11
Q

Aminoglycosides, 2nd and 3rd generation cephalosporins, and quinolones are examples of what type of antibiotic?

A

-Broad spectrum antibiotics

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12
Q

Antibiotics mechanism of action targets:

A
  • bacterial cell wall biosynthesis
  • cell membrane function
  • protein synthesis
  • RNA and DNA synthesis
  • Metabolic processes
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13
Q

An antimicrobial agent that binds enzymes transpeptidase/ penicillin binding proteins. They contain 4-membered nitrogen-containing beta-lactam ring at the core of their structure.

A

Beta-Lactams

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14
Q

Give the 4 beta-lactam class

A
  • Penicillin, Cephalosporins, Monobactam, and Carbapenems
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15
Q

Penicillin were found to inhibit the growth of what bacteria?

A

Streptococcus aureus

  • discovered by Alexendar Fleming in 1928
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16
Q

On what year do humans first started the use of Penicillin?

A

1941

  • from the mold penicillum notatum
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17
Q

To be effective Penicillin must:

A
  • penetrate the bacterial cell wall
  • keep its beta-lactam ring intact
  • binds to transpeptidase
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18
Q

How can bacteria develop resistanc to penicillins?

A
  • by producing penicillinase that binds to C-N bond of the beta-lactam ring
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19
Q

What bacterial structure provide antibiotics resistance gene to the cell?

A
  • Plasmids
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20
Q

The “first true antibiotic”

A

Penicillin

  • Fleming discovered that the mold penicillum notatum can inhibit S. aureus
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21
Q

These antibiotics are structurally similar to penicillin but can more withstand the action of beta-lactamase and are more modifiable

A

Cephalosporins

-Beta-lactams bind to and block the activity of enzymes responsible for making peptidoglycan, resulting in cell wall death.

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22
Q

What is beta-lactamase? and how do they inactivate antibiotics?

A

Beta-lactamases are enzymes produced by bacteria that provide multi- resistance to β-lactam antibiotics

-The beta-lactamase enzymes inactivate beta-lactam antibiotics by hydrolyzing the peptide bond of the characteristic four-membered beta-lactam ring rendering the antibiotic ineffective.

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23
Q

This antibiotic only has 1 beat-lactam ring, its ring is alone and not fused to another ring (in contrast to other beta-lactams which have at least two rings).

A

Monobactam

  • can kill tough hospital acquired, MDR bacteria
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24
Q

This antibiotics can work only against aerobic gram-negative bacteria. They are actually referred to as “magic bullet” for gram-negative aerobic bacteria.

A

Monobactam

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25
Q

Type of antibiotic given as initial treatment for px with infectious diseases

A

Broad-spectrum antibiotics

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26
Q

Type of antibiotics given to px that has an infectious diseases with known organism

A

Narrow spectrum

-given when test result us already out and the organism is already identified

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27
Q

Characteristic of antimicrobial agents

A
  • Must be in active form
  • must be able to achieve concentration at the site of infection that is higher than the pathogens’s MIC to be effective
  • must jave selective toxicity
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28
Q

The lowest concentration of drug that inhibits the bacteria.

It is the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation

A

MIC- minimum inhibitory concentration

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29
Q

It is the study of a drug’s molecular, biochemical, and physiologic effects or actions. It answers the questions

“What the drug does to the body?”

A
  • Pharmacodynamics
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30
Q

The study of how the body process the drugs. It answers the question

“what the body does to the drugs”

A

Pharmacokinetics

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31
Q

Classification of antimicrobial drugs according to nature

A
  • Natural drugs
  • Semi synthetic drugs
  • Synthetic drugs
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32
Q

Drugs produced by bacteria or fungi

ex. bacitracin, erythromycin, vancomycin, penicillin, tetracyline

A

-Natural drugs

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33
Q

These are modified natural drugs with added chemicals

ex: ampicillin, carbenicillin, and methicillin

A

Semi-sybthetic drugs

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34
Q

These are chemically-produced drugs

ex: sulfonamides, isoniazid, ciprofloxacin, and dapsone

A

Synthetic ic drugs

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35
Q

These are the most selective antibiotics according to mode of action with a high therapeutic index.

Note: TI means the quantitative measurement of the relative safety of drugs.

A

-Cell wall inhibitors antibiotics

36
Q

Formula for therapeutic index

Note: the larger the TI the safer the drugs is

A

TI = TD 50
————–
ED 50

in which TD refers to- toxicity dose
ED refers to - effectivity dose

37
Q

An enzyme also called as penicillin binding protein

A

Transpeptidase enzyme

  • which is necessary for cell wall synthesis. It also helps bacteria to form cross-linking between each peptide chains.
38
Q

What substance is found in the cell wall of gram positive bacteria and are composed of polymers of either glycerol phosphate and ribitol phosphate. They are also involved in attachment of bacteria to mucosal cells.

A

Teichoic acid

  • Teichoic acids (TAs) are specific polymers on Gram-positive bacterial cell surfaces and are not found in Gram-negative bacterial cells
39
Q

Process of Beta-Lactam inhibition

A 
Beta lactam 
        | ring attached  to PBP or transpeptidase enzyme
        ↓
Interference with transpeptidation 
        ↓
Inhibition of cell wall synthesis
        ↓
Unstable cell wall 
        ↓
Autolysis due to osmotic pressure 
        ↓ 
Cell death
40
Q

Refers to an enzyme which can inactivate penicillin, produced by certain bacteria. These are bacteria that breaks the lactam ring of beta-lactam classes

A

Penicillinase

  • e.g. B-lactamase
41
Q

Common resistance mechanism of bacteria to beta-lactam antibiotics

A

-production of enzymes such as b-lactamase or penicillinase

42
Q

What do beta-lactams inhibit?

A

inhibits transpeptidation

43
Q

How do bacitracin inhibit bacterial growth?

A

inhibits synthesis of peptidoglycan precursors.

44
Q

How do vancomycin inhibits bacterial cell growth?

A

-they inhibit translocation and elongation of peptidoglycan

45
Q

Target site for protein synthesis inhibitors

A
  • Ribosomes
46
Q

2 ribosomal sub units of prokaryotic organism

A
  • 30S and 50S subunit
47
Q

These type of antibiotic inhibitors binds with a 30s and 50s subunit that results in the misreading of mRNA and thus interferes with aminoacyl-tRNA binding.

A

Protein synthesis inhibitors

  • always halt the growth of microorganism
  • bacteriostatic in nature
48
Q

Main side effect of aminoglycosides

this include: gentamicin, kanamycin, neomycin, streptomycin, tobramycin

A

Deafness and loss of balance

49
Q

Antibiotics usually used to treat typhoid fever, meningitis, and some anaerobic organism.

A

-Chloramphenicol

50
Q

Primary side effects of chloramphenicol

A

Temporary or permanent depression of bone marrow resulting to Aplastic anemia and Leukopenia

51
Q

Increase dosage of tetracycline may lead to _______ and ______ damage or even ______ of the teeth among children

A
  • Hepatic and kidney

- yellowing of teeth

52
Q

Type of antibiotic according to mechanism of action that primarily target DNA metabolism. Antibiotics that targets organism before translation.

A

Nucleic Acid Synthesis Inhibitors

53
Q

A type of nucleic acid inhibitor antibiotic that inhibit RNA POLYMERASE

A

Rifampicin

-indirectly stops protein production

54
Q

A type of nucleic acid inhibitor antibiotic that interferes with DNA gyrase (G-) and Topoisomerase IV (G+)

The enzymes mentioned are necessary for DNA replication ,recombination, and repair.

A
  • Flouroquinolones

e. g. Ofloxacin and Ciprofloxacin

55
Q

A type of nucleic acid inhibitor antibiotic that disrupts DNA process and is effective against anaerobic bacteria

A

Metronidazole

56
Q

Type of antibiotics that disrupts cell membrane function, once the cell membrane is disrupted. It increase permeability resulting to autolysis and cell death.

A

Cell membrane inhibitors

57
Q

A cell membrane inhibitor that is effective against gram-negative bacteria such as Pseudomonas aeruginosa

A

-Polymyxin B nd E

58
Q

A cell membrane inhibitor that is effective against gram-negative bacteria such as Pseudomonas aeruginosa

A
  • Polymyxin B nd E

- acts as detergents interacting with phospholipids in cell membrane to increase permeability.

59
Q

A cell membrane inhibitor that is effective against gram-positive bacteria like MRSA and VRSA

A

Daptomycin

  • exerts antimicorbial effect by binding and disrupting gram- positive bacteria
60
Q

A type of metabolite inhibitor antibiotics that inhibits FOLIC acid metabolism and has high therapeutic index.

It targets the enzyme dihydropteroate synthetase

A

-Sulfamethoxazole (SMXZ)

61
Q

A type of metabolite inhibitor antibiotics that blocks the enzyme dihydrofolate reductase which is necessary in the formation of DNA

A
  • Trimepthoprim

- usually mixed w/ sulfonamides which enhance activity against bacteria.

62
Q

A type of metabolite inhibitor antibiotics that interferes CORD factor synthesis found in mycolic acid

A

-Isoniazid

63
Q

MALT = Proteins synthesis

A

Macrolides- Aminoglycosides- Lincosamides- Tetracycline

64
Q

Genral Antibiotic classes

“Antibiotics Can Terminate Protein Synthesis For Microbial Cells Like Germs”

A

Aminoglycosides- Cephalosporins- Tetracyclin- Penicillins-Sulfonamides- Fluoroquinolones- Macrolides-Carbapenems- Lincosamides- Glycopeptides

65
Q

It is a result of both use and overuse of antimicrobial agents

A

Antibiotic Residtance

66
Q

Two types of antimicrobial resistance

A

Intrinsic and Acquired resistance

67
Q

Refers to the type of antibiotic resistance in which the organism already had inherent characteristic enabling it to be resistant to certain antimicrobials even before antibiotic use.

A

Intrinsic Resistance

68
Q

Characteristic of Intrinsic Resistance

A
  • already included in the normal genetic structure of the organism
  • depends on the hydrophobic and hydrophilic nature of antibiotic
  • Impermiability of antibiotic to cell wall
  • Pass vertically into the new cell
  • Predictable
  • Naturally and consistently inherited
69
Q

Refers to the type of antibiotic resistance which is necessitated by prior exposure to the antimicrobial agent. Usually results from altered cellular physiology and structure caused by changes in microorganism genetic make-up.

Characteristics:

  • present only on certain isolates different from the parental strain
  • Unpredictable
A

Acquired Resistance

70
Q

Primary reason as to why laboratory methods are necessary to detect resistance pattern which are known as antimicrobial susceptibility profile in clinical isolates

A

Unpredictability of acquired resistance

71
Q

Common methods for an organism to attain acquired resistance

A

-chromosomal mutations, transformation, and recombination

72
Q

Bacterial resistance to beta- lactams may be mediated by:

A
  • enzymatic destruction (production of b-lactamase)
  • altered target - resulting low affinity
  • Decreased uptake or increase efflux of drugs
73
Q

In gram positive bacteria, B-lactamase is secreted as?

A

Exoenzymes

  • offering less protection to organism (kay sa gawas man na produce)
74
Q

In gram negative bacteria, B-lactamase are found in?

A

Periplasmic space

75
Q

4 categories of Beta-lactamases

A
  • Class A,B, C, and D enzymes
76
Q

type of B-lactamase enzyme that is SERINE peptidases and is usually carried by plasmids .

A

Class A and D enzymes

77
Q

type of B-lactamase enzyme that is CEPHALOSPORINASE and is usually located within and integron

A

Class C enzyme

78
Q

type of B-lactamase enzyme that is METALLO-BETA LACTAMASES and is usually located within and integron

A

Class B enzyme

79
Q

These are inhibitor drugs that are co-administered with beta-lactam antimicrobials to prevent antimicrobial resistance by inhibiting serine beta-lactamases, which are enzymes that inactivate the beta-lactam ring, which is a common chemical structure to all beta-lactam antimicrobials.lactamase

Note: these combination is effective only against organism that produce beta-lactamase

A

B-lactamas inhibitors

e.g. Clavulanic acid, sulbactan, and tazobactam

80
Q

Are rapidly evolving group of beta-lactamases which shares the ability to hydrolyze 3rd generation cephalosporins and aztreonam but are inhibited by clavulinic acid.

A

Extended spectrum B-lactamases (ESBLs)

81
Q

Antibiotic drugs that is used for treatment of Extended spectrum b-lactamases because they are active against it

A

Carbapenems

82
Q

For screening of Extended spectrum b-lactamases it should b resistant to antibiotics such as:

A
  • Ceftazidime, Cefotaxime, Cefpodoxime
83
Q

What confirms ESBLs production of bacteria in culture plate

A

-Synergy or key-hole phenomenon between antibiotic drugs

84
Q

It is a circular area around the spot of the antibiotic in which the bacteria colonies do not grow. This can be used to measure the susceptibility of the bacteria to wards the antibiotic.

A

Zone of inhibition / Zone of no growth

  • key hole phenomenon
85
Q

Measurement necessary for it to be deemed as positive for ESBLs.

A

≥5 mm enhancement with Clavunilic combination

BACTERIOLOGY (15 decks)

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