Ch. 24 - Antibiotics Flashcards Preview

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Flashcards in Ch. 24 - Antibiotics Deck (27):
1

cell wall synthesis inhibition

penicillin

cephalosporins

carapenems

vancomycin

isoniazid

lysozyme (not an antibiotic)

2

DNA synthesis inhibition

sulfonamides

fluoroquinolones (ciproflaxin)

3

protein synthesis inhibition - 30s subunit

aminoglycosides

tetracyclines

4

protein synthesis inhibition - 50s subunit

chloramphenicol

macrolides

lincosamides (clindamycin)

streptogramins

oxazolidinones

5

RNA synthesis inhibition

rifampin

6

sulfanamides

SPECTRUM: broad

EFFECT: bacteriostatic

MECHANISM: competitive inhibition with PABA -- inhibit folic acid synthesis

7

fluoroquinolones (ciproflaxin)

SPECTRUM: broad

EFFECT: bactericidal

MECHANISM: inhibit DNA gyrase

8

penicillin - natural (Penicillin G, Penicillin V)

SPECTRUM: narrow (Gram Positive)

EFFECT: bactericidal (in rapidly multiplying bacterial cells - infection); bacteriostatic (slowly multiplying cells)

MECHANISM: bind to PBP transpeptidase (competitive inhibitor); conformation mimics D-ala-D-ala of NAM penta-peptide; inhibit cross-linking

9

aminopenicillins (amoxicillin, ampicillin)

SPECTRUM: broad - Gram Positive, partial Gram Negative

EFFECT: bactericidal

combine with beta-lactamase inhibitors: bind to active site of beta-lactamse =
Amoxicillin + Clavulanic Acid = Augmentin
Piperacillin + Taxobactum = Zosyn

10

beta-lactamase

(penicillinase)

Inactivate penicillin

Hydrolyze bond in beta-lactam ring; convert to harmless pencilloic acid

11

cephalosporins (generations 1-4)

SPECTRUM: narrow to broad - enhanced Gram Negative in higher generations; Gen 4 both Gram Positive and Gram Negative ; broader than penicillins - longer lasting in body; fewer allergic rxns

EFFECT: bactericidal

MECHANISM: bind PBP; mimic D-ala-D-ala; disrupt cross links in peptidoglycan

more resistant to beta-lactamases due to conformational shape

Used when have penicillin allergy

12

cell membrane function inhibition

bacitracin

polymyxin

gramicidin

12

Carbapenems (meropenem, imipenem)

SPECTRUM: broad - Gram Positive and Gram Negative

EFFECT: bactericidal

MECHANISM: PBP; inhibit cross links in peptidoglycan

Structure makes highly resistant to beta-lactamase

Imipenem - degrades kidneys; administer with cilastatin = Primaxin

Antibiotic of last resort

Gut bacteria developing carapenems - no new antibiotic to combat resistance

Structure highly resistant to beta-lactamases

Drug of last resort

13

vancomycin

SPECTRUM: narrow - Gram Positive (too large to fit through porins to affect Gram Negative)

EFFECT: bactericidal

MECHANISM: inhibit cell wall mucopeptide synthesis -- H bond with terminal D-ala-D-ala; transpeptidase cannot bind

VRSA: DalaDala to DalaDlac

Drug of last resort - MRSA, C.diff

14

isoniazid

SPECTRUM: narrow - mycobacterium

EFFECT: bacteriostatic

MECHANISM: inhibition of mycolic acid (fatty acid cell wall) in mycobacterium

Treatment of TB: isoniazid, rifampin, and ethambutol

15

lysozyme

not an antibiotic!

SPECTRUM: narrow - Gram Positive

EFFECT: bactericidal

MECHANISM: hydrolyze glycosidic bond (beta 1-4) between NAM and NAG; cleaved bond -- break of peptidoglycan

16

bacitracin

SPECTRUM: narrow - Gram Positive

EFFECT: bactericidal

MECHANISM: interferes with NAM precursor transport through plasma membrane; binds to transport protein in cell membrane that would bind NAM precursor

bacitracin + polymyxin + neomycin = Neosporin

17

polymyxin

SPECTRUM: narrow - Gram Negative

EFFECT: bactericidal

MECHANISM: insert into cell membrane -- increase permeability of cell membrane (increase osmotic pressure -- cell lysis)

18

aminoglycosides

(gentamycin, neomycin, streptomycin)

SPECTRUM: narrow - Gram Negative

EFFECT: bactericidal

MECHANISM: bind to 30s subunit; inhibition of initiation complex; misreading of genetic code

Streptomycin - sometimes treatment for TB
Gentamycin - treatment against UTI
Neomycin - cuts/abrasions (bacitracin + polymyxin + neomycin = Neosporin)

19

tetracyclines

SPECTRUM: broad

EFFECT: bacteriostatic

MECHANISM: bind to 30s subunit; block attachment of aminoacyl tRNA (no initiation)

Benzene ring formation

Can destroy microbiota with prolonged used

Cause staining in teeth

Affects bone development - do not give to children and pregnant women

To treat infection diseases - rickettsia and chlamydia

20

chloramphenicol

SPECTRUM: broad - Gram Positive, Gram Negative, Rickettsia, Chlamydia

EFFECT: bacteriostatic

MECHANISM: bind to 50s subunit; misreading of the genetic code (inhibit peptide bond formation)

small molecule

only for life-threatening illnesses (toxicity limits use):

-Gray Syndrome: chloramphenicol accumulates in blood of newborns, toxic rxn, sudden breakdown of cardiovascular system

-aplastic anemia: bone marrow stops producing RBCs (bone marrow suppression


21

macrolides (erythromycin)

SPECTRUM: broad - Gram Positive infections

EFFECT: bacteriostatic

MECHANISM: bind to 50s subunit; inhibit chain elongation (blocks translocation)

useful antibiotic - very few side effects

to treat: primary atypical pneumonia (mycoplasma pneumonia, legionnaire's disease)

for pts with penicillin allergy

22

lincosamides (clindamycin)

SPECTRUM: Gram Positive and anaerobic infections

EFFECT: bacteriostatic

MECHANISM: bind to 50s subunit; inhibit chain elongation (block ribosomal translocation)

Use against penicillin- resistant bacteria

limit use to serious infections: precipitates C. diff - eliminates competing organisms from GI; permit C.diff to overgrow the area

23

Pseudomembranous Colitis

from Clostridium difficile (C.diff)

membranous lesions cover intestinal wall

watery diarrhea, fever, dehydration

25

streptogramins

SPECTRUM: broad - Gram Positive

EFFECT: bactericidal

MECHANISM: bind to 50s subunit - premature chain termination

found in 1962

26

oxazolidinones

SPECTRUM: Gram Positive

EFFECT: bacteriostatic

MECHANISM: bind to 50s subunit; interfere with chain initiation

discovered in 2001

drug of last resort - toxic to mitochondria
produce allergic rxns

27

rifampin

MECHANISM: interfere with RNA synthesis -- affect transcription (inhibits RNA polymerase)

Treatment of: meningitis, TB, leprosy

Resistance to mycobacterium - given in combo with isoniazid and ethambutol

Can cause liver damage