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Microbiology > Antimicrobial Agents > Flashcards

Antimicrobial Agents Flashcards

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Biology 101 flashcards
1
Q

What 4 classes of antibiotics cover primarily one gram class?

A

“GLAM”

glycopeptides +
lincosamides +
aminoglycosides -
macrolides +

the rest cover both gram negative and positive

amiNOglycosides = gram Negative

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2
Q

Sulfonamides Mechanism

A

SulFOnamides inhibit Folate synthesis

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3
Q

Fluoroquinolones Mechanism

A

fluoroQUINolones– think of QUIN as quintuplets… multiple “replicated” babies

so fluoroquinoloes inhibit DNA replication

block both topoisomerase IV and DNA gyrase

usually for bacterial infections of the skin, sinuses, kidneys, bladder, and also used for bacterial infections causing bronchitis or pneumonia

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4
Q

Classes that Inhibit Protein Synthesis

A

“MALT”

macrolides (50S)
aminoglycosides (30S)
lincosamides
tetracyclines (30S)

aminoglycosides: blocks translation (streptomycin)
tetracyclines: block tRNA attachment

Macrolides: prevent continuation of protein synthesis after binding 50S ribosome (chloramphenicol)

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5
Q

Classes that inhibit cell wall synthesis

A

“Giant Cats Crush Peptidoglycan”

glycopeptides
cephalosporins
carbapenems
penicillins

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6
Q

Synergistic Drug Combination

A

action of one drug enhances the other

an agent that damages the cell wall can increase entry of another agent that isn’t normally allowed into the cell

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7
Q

Antagonistic Drug Combination

A

activity of one drug interferes with another

ex. an agent that needs cell growth is used with a bacteriostatic agent

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8
Q

Different Mechanisms of Antibacterial Drugs

A
  1. inhibit cell wall synthesis
  2. inhibit protein synthesis
  3. inhibit nucleic acid synthesis
  4. injury to plasma membrane
  5. inhibit synthesis of essential metabolites
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9
Q

Name the beta-lactam antibiotics and describe their mechanism

A

Cell wall, bactericidal, require cell growth

“MP triple-C”

monobactams
penicillins
cephalosporins
cephamycins
carbapenems

Tpase recognizes the beta lactam ring C-N bond and binds it to attach it to peptidoglycan, thinking it is D-ala-D-ala. This complex cannot be broken, so Tpase is irreversibly inactivated

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10
Q

Transpeptidase function and antibiotics targeting transpeptidase

A

Tpase crosslinks glycan strands in peptidoglycan

beta-lactams inhibit Tpase, so glycan strand cannot be joined

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11
Q

Penicillin Binding Proteins (PBPs)

A

Beta lactams target PBPs

PBPs include:

  • transpeptidases (Tpase)
  • carboxypeptidases
  • endopeptidases
    • all are involved in the later stages of peptidoglycan synthesis and reshaping the cell wall during growth and cell division
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12
Q

Penicillin G

A

First beta lactam antibiotic

only gram positive

acid and alkali-labile

inactivated by beta-lactamases (penicillinases)

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13
Q

6-aminopenicillanic acid (6-APA)

A

can produce penicillins synthetically starting with 6-APA as a precursor

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14
Q

Penicillins that are improvements over Penicillin G

A

better acid stability: amoxicillin and cloxacillin

broader spectrum (includes gram negative): ampicillin, amoxicillin, carbenicillin

increased bioavailability: ampicillin, pivampicillin

resistance to beta-lactamases: methicillin, cloxacillin

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15
Q

Beta Lactamase Inhibitors

A

clavulanic acid, sulbactam, tazobactam

can overcome beta lactamase resistance by using a beta lactam drug in combination with a beta lactamase inhibitor

Popular combinations:

  • amoxicillin and clavulanate (augmentin)
  • ampicillin and sulbactam (unasyn)
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16
Q

Carbapenems (Important General Info)

A

beta lactams

combine features of penicillins and cephalosporins

used to treat infections by multi drug-resistant bacteria (MDR bacteria)

excellent activity against a broad spectrum of gram positive and gram negative

ESBLs do NOT inactivate carbapenems

17
Q

Thienamycin

A

carbapenem

penetrates easily through the outer membrane of gram negative bacteria through porins

resistant to ESBLs (like all carbapenems)

18
Q

Monobactams

A

narrow spectrum targeting aerobic gram negative

useful for people with penicillin allergies

ex. aztreonam (azactam)

19
Q

Bacitracin

A

non beta lactam cell wall inhibitor

polypeptide antibiotic

interferes with lipid carrier that takes peptidoglycan monomers across the cell membrane

side effect: can interfere with sterol biosynthesis in humans, so it is used ONLY TOPICALLY

20
Q

Neosporin Contents

A

Polymyxin B: gram negative rods

Bacitracin zinc: gram positive

Neomycin sulfate: broad spectrum

** only used for broad spectrum topical use

21
Q

Vancomycin

A

glycopeptide

non beta lactam cell wall inhibitor

gram positive, bactericidal

important in methicillin and cephalosporin resistant organisms

vancomycin binds D-ala-D-ala at the end of the peptidoglycan precursor so that transpeptidase “cannot reach” to make the bond

22
Q

Streptomycin

A

amino glycoside

bactericidal, broad spectrum

NOT effective against anaerobes or intracellular bacteria

can cause kidney and/or 8th CN damage

** gentamicin, amikacin, and tobramycin have extended spectra, including activity against pseudomonas

23
Q

Tetracyclines

A

tetracycline, minocycline, doxycycline

bacteristatic broad spectrum
includes mycoplasma, rickettsia, chlamydia

block acceptor site so that aminoacyl-tRNA cannot bind

can cause permanent discoloration of teeth and enamel hypoplasia when given during tooth development– do not give to pregnant women or children under 8 years old

24
Q

Erythromycin

A

macrolide (50S)

bacteriostatic

gram positive, mycoplasma, chlamydia

bind 2 sites on 50S ribosome causing dissociation of tRNA and termination of peptide linking

stomach acid hydrolyzes erythromycin and the metabolites irritate the stomach.
azithromycin and clairithromycin are more acid stable so you have more time between doeses

14- membered lactone ring

25
Q

Azithromycin and Clairithromycin

A

macrolide that is newer and more active

drug concentration increases at the site of infection because they are taken up by phagocytes and delivered to the infection

26
Q

Clindamycin

A

bacteriostatic– inhibits peptide transfer

spectrum like erythromycin plus very effective against anaerobes in general

Serious side effect: pseudomembranous colitis caused by C. difficile overgrowth in the enteric flora

27
Q

Chloramphenicol

A

bacteriostatic, broad spectrum

mainly inhibits peptide transfer

penetrates human mitochondria and inhibits mitochondrial protein synthesis– causes bone marrow depression side effect

restricted to serious infections that cannot be treated with other agents

28
Q

Quinupristin/Dalfopristin (Synercid)

A

bactericidal, gram positive including MRSA and VR enterococci

combination of 2 bacteriostatic streptogramin agents

block ribosome channels where newly made proteins are “spit out”

29
Q

Rifamycins (rifampin, rifampicin)

A

nucleic acid synthesis inhibitor

block prokaryotic RNA polymerase from initiating transcription, so RNA synthesis is blocked.

used for tuberculosis, leprosy, and legionnaire’s disease

30
Q

Sulfonamides and Folate Reductase Inhibitors

A

Inhibit synthesis of essential metabolites (block purine and pyrimidine synthesis)

sulfonamides and trimethoprim inhibit sequential steps in bacterial folic acid synthesis. They are used together because of their similar half lives

31
Q

Antibiotics that Injure the Plasma Membrane

A

Polymyxin B: binds outer membrane of gram negative bacteria and alters permeability, leading to cell death.

These drugs also bind eukaryotic cells to some extent so they can only be used topically (Neosporin)

32
Q

Linezolid (Zyvox)

A

oxazolidone (class)
bacteriostatic against gram positive

potential VRSA treatment

bind near peptide transferase center on the 23s RNA and block interaction of the 50S subunit with fMet-tRNA (remember fMet is the start protein for bacterial translation)

Microbiology (2 decks)

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