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Antibiotics Flashcards

0
Q

Penicillin V

A

Beta-lactam, penicillin
Acid-resistant (can take orally)
Sensitive to penicillinases
Limited spectrum (YES G+, G- cocci, NO G- rods)

Similar: Penicillin VK (+ potassium, more soluble)

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1
Q

Penicillin G

A

“Original” penicillin
Beta-lactam
Acid labile - can’t take orally (only IV, IM)
Sensitive to penicillinases
Limited spectrum (G+ and G- cocci - NOT enteric G- rods)
- Neisseria meningititis
- Treponema pallidum (syphilis)

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2
Q

Ampicillin

A

Beta-lactam (penicillin)
Sensitive to penicillinase
Acid stable
Broader spectrum - G- enteric, most G+

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3
Q

Amoxicillin

A

Beta-lactam (penicillin)
Sensitive to penicillinase
Acid stable
Broader spectrum - G- enteric, most G+

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4
Q

Tricarcillin

A 
Beta-lactam (carboxypenicillin)
Sensitive to penicillinase
Acid stable
Extended spectrum
 - effective against G- enteric (including Pseudomonas aeruginosa)
 - less action against G+
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5
Q

Piperacillin

A 
Beta-lactam (ureidopenicillin)
Sensitive to penicillinase
Acid stable
Extended spectrum
 - most effective against Pseudomonas aeruginosa, anaerobic, G-
 - less effective against G+
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6
Q

Methicillin

A 
Beta-lactam (penicillin)
Resistant to penicillinase
Acid labile
Altered spectrum
 - targets Staphylococcus aureus (MRSA = resistant)
 - not effective vs G-
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7
Q

Oxacillin

A 
Beta-lactam (penicillin)
Resistant to penicillinase
Acid stable (vs methicillin)
Altered spectrum
 - targets Staphylococcus aureus
 - not effective vs G-

Similar: naficillin, dicloxacillin

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14
Q

Penicillins

A

Beta-lactam ring + thiazolidine ring + R group
Bacteriocidal but only if cell is growing
Inhibit cell wall synthesis -> lysis

PBP = transpeptidase = penicillin binding protein

Resistance = beta-lactamase (hydrolyzes ring)
- often acquired on plasmid

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15
Q

Cephalosporins

A 
Sim to penicillins - beta lactam
 - bacteriocidal when dividing
Dihydrothiazide ring -> 
More resistant to penicillinases, acid
Can use if penicillin allergy

Broad spectrum - most Gram +, some Gram -

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16
Q

Cefazolin

A

1st gen cephalosporin (beta lactam)

Most Gram +
Some Gram -
Not pseudomonas aeruginosa

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17
Q

Cefuroximide

A

2nd generation cephalosporin (beta lactam)

More Gram -
Fewer Gram +
Not pseudomonas aeruginosa

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18
Q

Ceftriaxone

A

3rd generation cephalosporin (beta lactam)

Penetrates blood-brain barrier

Most Gram -

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19
Q

Ceftazimide

A

3rd generation cephalosporin (beta lactam)

Broad spectrum Gram -
Effective against Pseudomonas aeruginosa

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20
Q

Aztreonam

A

Mono-bactam (sim to beta-lactam but resistant to breakdown)

Aerobic Gram -
includes Pseudomonas aeruginosa
Not Gram + or anaerobic

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21
Q

Imipenem

A

Carbapenem (beta lactam)

Broadest spectrum vs Gram -
MRSA variable

Susceptible to renal dipeptidases

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22
Q

Clavulonic acid

A

Beta-lactamase inhibitor

+ amoxicillin = Augmentin

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23
Q

Sulbactam

A

Beta-lactamase inhibitor

+ ampicillin = Unasyn

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24
Q

Vancomycin

A

Glycopeptide - inhibits cell wall synthesis
Blocks transfer of D-Ala-D-Ala
Toxic

Only Gram + (too big for outer membrane porins)
Enterococcus or staphylococcus (ex MRSA)
Oral for C diff
Resistance is possible

25
Q

Cycloserine

A

D-Ala analog -> blocks cell wall synthesis
Toxic

Tuberculosis

26
Q

Bacitracin

A

Blocks phosphatase in murein (cell wall) synthesis
Toxic -> topical only

Only Gram +

27
Q

Polymyxin B

A

Disrupts membrane permeability (-> cidal even without growth)
Toxic -> topical

Gram - enterics (including Pseudomonas)

28
Q

Aminoglycosides

A

Distort 30S subunit -> cidal
Require aerobic conditions, some metabolic activity for entry into cell
Toxic

29
Q

Streptomycin

A

Initial aminoglycoside

Aerobic conditions, metabolic activity, imperfections ->
Entry -> distorts 30S -> misreading -> funny proteins ->
Disrupts membrane -> cidal

Lots of resistance
Toxic
Used for TB

30
Gentamycin
Aminoglycoside Multiple inhibitions to 30S (less resistance than streptomycin) Toxic (nerve, renal) - not generally used
31
Tetracyclines
also includes doxycicline and monocycline Block tRNA-30S binding -> static Broad spectrum - mycoplasma, rickettsia, chlamydia - GI microbiome changes Teratogenic, yellow teeth in kids
32
Erythromycin
Macrolide Blocks 50S chain elongation -> static Most Gram + Mycoplasma Chlamydia
33
Azythromycin
Similar to erythromycin (macrolide, blocks chain elongation) High concentrations at infection site dt macrophages
34
Chloramphenicol
Blocks chain elongation -> static Aplastic anemia - not commonly used Anaerobes - Bacteriodes fragilis
35
Clindamycin
Blocks peptidyl transfer -> static Some Gram + Anaerobes
36
Streptogramins
``` New class Binds to 50S -> static ``` Dalfopristin + quinopristin = Synergin (work synergistically) MRSA, VRE, etc
37
Oxazolidinones
aka linezolid, Zyvox Blocks tRNA transfer -> static Gram + New -> VRE, MRSA, etc - some resistance already
38
Mupirocin
Block isoleucine aminoacyl transferase -> - static at low, cidal at high Topical vs MRSA (surgeons) Impetigo (Staph aureus, Strep pyogenes)
39
Quinolones
aka Ciprofloxacin, Moxifloxacin Inhibits gyrase -> DNA synthesis -> cidal Inhibits bone growth -> teratogen, kids ``` Gram + cocci Enteric Gram - bacilli - includes Pseudomonas aeruginosa Anthrax prophylaxis No longer MRSA (resistance) ```
40
Metronidazole
Requires anaerobic conditions -> ferredoxin reduces/activates Fragments DNA -> cidal Bacteroides Protozoal - trichomaniasis, amebiasis
41
Rifampin
Inhibits RNA synthesis -> cidal Broad spectrum Tuberculosis (with isoniazid) Saliva prophylaxis (Neisseria meningititis)
42
Ethambutol
Unknown mechanism Static Tuberculosis
43
Isoniazid
Blocks InhA enzyme -> mycolic acid -> cell wall -> cidal Tuberculosis
44
Pyrazinamide
Unknown mechanism Activated by amidase -> cidal Tuberculosis
45
Reasons to give two drugs
``` Synergism Susceptibility pattern Decreased resistance Lower dose of toxic drug Polymicrobial infection ```
46
Mechanisms of resistance
Enzymatic degradation (Beta-lactam, aminoglycoside, chloramphenicol, erythromycin) Decreased permeability (penicillins, chloramphenicol, aminoglycoside) Active efflux (tetracycline) Altered targets (vancomycin, erythromycin, streptomycin, methycillin, sulfonamide, trimethoprim) Alternative pathway (trimethoprim)
47
Sulfonamide
Analog of PABA -> blocks THF production -> static Wide range Protozoa UTI
48
Trimethoprim
Blocks DHF reductase -> THF synthesis -> static (same enzyme in humans but much higher affinity) UTI (Bactrim = combo with sulfa)
49
Antibiotic sensitivity methods
Minimum inhibitory concentration - Determine via tube dilution -> no growth Minimum bactericidal concentration - requires tube -> plate -> no growth after removed Disc diffusion - simple, simultaneous, doesn't determine MBC Betalactamase production - nitrocefin = chromogenic
50
Ideal antibiotic properties
Kill bacteria, no toxicity or allergy to host Should kill faster than it is inhibited Should kill faster than resistance develops Should reach bacteria (abcess, brain, inside cells) Ideal does NOT exist...
51
Major classes of antibiotics
Antimetabolites - sulfonamides, trimethoprim, isoniazid Inhibitors of cell wall synthesis - beta-lactams, glycopeptides Membrane permeability - polymyxins Inhibitors of protein synthesis - aminoglysides, macrolides, tetracycline, chloramphenicol Inhibitors of nucleic acid synthesis - quinolone, rifampin

Microbiology (23 decks)

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