Q2: Micro: Antibiotics Ii

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I.
*ANTIBIOTICS THAT AFFECT MEMBRANE PERMEABILITY *

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POLYMYXIN B and E

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POLYMYXIN B and E

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C/S: cidal agent

TARGET: gram -ve enteric rods especially PSEUDOMONAS

MECHANISM:
1) first binds to -ve LPS in outer membrane, the cute phospholipids cause a membrane leak
2) topical

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INHIBITOR OF PS

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1) STREPTOMYCIN
2) GENTAMICIN
3) TETRACYCLIN
4) DOXYCYCLIN
5) TIGECYCLIN

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II. INHIBITORS OF PROTEIN SYNTHESIS

* AMINOGLYCOSIDES *

1) STREPTOMYCIN

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C/S: cidal but not lytic

TARGET: tuberculosis

MECHANISM: not really used in therapy anymore
- +vely charged at physiological ph and does not penetrate the bacteria readily

1) specifically acts on 30S ribosomal substrate
2) binds 30S and distorts reading so that "bad" protein is made and it causes membrane leakiness
3) it inhibits the formation of initiation complex and peptide bonding
4) streptomycin selects for mutants

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* OTHER AMINOGLYCOSIDES *

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GENTAMICIN

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2) GENTAMICIN

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C/S: CIDAL

TARGET:

MECHANISM:
- it inhibits 30S
- can't obtain resistance in one step like streptomycin
- TOXIC
- CAUSES DAMAGE TO CN VIII and renal function
- requires AEROBIC conditions to be effective

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* TETRACYCLINS *

3) TETRACYCLIN
4) DOXYCYCLIN
5) TIGECYCLIN

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C/S: STATIC

TARGET:
- mycoplasma
- ricketsia
- chlamydia

MECHANISM:
- widely used
- binds to 30S ribosomal subunit
- BROAD SPECTRUM action
- not given during pregnancy because it may cause ADVERSE EFFECTS
- not given to kids under 8 years old because may damage tooth enamel
- it's not a serious health hazard, but it is disfiguring

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* INHIBITS 50S *

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6) ERYTHROMYCIN
7) AZITHROMYCIN
8) CHLORAMPHENICOL
9) CLINDOMYCIN

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6) ERYTHROMYCIN

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C/S:N STATIC

TARGET:
- mycoplasm
- chlamydia

MECHANISM:
- blocks chain elongation
- similar to penicillin G

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7) AZITHROMYCIN

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C/S: STATIC

TARGET:

MECHANISM:
- higher activity
- BROADER SPECTRUM than erythromycin
- high concentration

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8) CHLORAMPHENICOL

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C/S:STATIC

TARGET: anaerobes (bowel, B. fragilis)

MECHANISM:
- blocks peptide chain elongation
- may cause lethal aplastic anemia

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9) CLINDAMYCIN

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C/S: STATIC

TARGET: gram +ve and moderately active anaerobes

MECHANISM:
- inhibits peptidyl transfer

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* INHIBITION OF TRANSLATION BY OTHER MECHANISM"

10) OXAZOLIDINONES
11) LINEZOLID

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C/S: STATIC

TARGET:
- gram +ve organisms

MECHANISM:
- can use for VREF, MRSA, VRSA
- oral intravenous interactions with 16S RNA etc..

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12) PREPTOGRAMINS
13) DALFOPRISTIN
14) QUINOPRISTIN (SYNERGIN)

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C/S: STATIC

TARGET:

MECHANISM:
- binds 50S, NEW
- MRSA, VREF and other resistant bacteria

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* INHIBITION OF TRANSLATION BY OTHER MECHANISMS *

15) MUPIROCIN

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C/S: STATIC/ CIDAL

TARGET:
- S. AUREUS
- S. PYOGENES

MECHANISM:
- an ab that binds specifically to TRNA synthetase to prevent its function
- no ILE- TRNA for PS
1) STATIC= LOW concentrations
CIDAL - HIGH concentrations

2) useful for MRSA, typical treatment for those bacteria

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IV. INHIBITOR OF DNA REPLICATION

* QUINOLONES *

1) CIPROFLOXACIN
2) MOXIFLOXACIN

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C/S: CIDAL

TARGET:
- gram -ve enteric bacilli
- gram +ve cocci
- p. aeruginossa

MECHANISM:
- these are FLUROQUINOLONES
1) do not have DNA gyrase (cidal)
2) increased resistance and it's no longer recommended for MRSA
3) should not be prescribed for pregnant women or chilren because they can damage growing bone

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* NITROMIDAZOLE *

3) METRONIDAZOLE

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C/S: CIDAL

TARGET:
- anaerobic drug
- useful against anaerobes, BACERIODES spp, protozoa (trichomoniasis, amebiasis)

MECHANISM:
1) binds DNA and fragments it
2) it requires anaerobic conditions

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VI. INHIBITS RNA SYNTHESIS

1) RIFAMPIN

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C/S: CIDAL

TARGET:
- N. MENINGITIDIS

MECHANISM:
- BROAD SPECTRUM BASED
- inhibits transcription by binding to B subunit of DNA pol to inhibit specific binding to DNA

1) used in combination with otehr drugs because of resistance
2) effective secretions in saliva, which is good as a prophylactic

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VII. OTHER AB

1) ETHAMBUTOL

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C/S: STATIC

TARGET:
- TUBERCLE BACILLI

MECHANISM:
- anti- TB drug
- unknown action

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2) PYRAZINAMIDE

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C/S: CIDAL

TARGET:
- MYCOBACTERIA (AN IMPORTANT ANTI- TB DRUG)

MECHANISM:
- ANTI- TB

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** ANTI- FUNGAL DRUGS! **

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*

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I. MEMBRANE PERMEABILITY

* POLYENE *

1) AMPHOTERICIN B
(NYSTATIN)

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C/S: CIDAL

TARGET:

MECHANISM:
1) binds to sterold in CM
2) selective toxicity- - binds better to ergosterol
3) poorly absorbed in GI
4) NYSTATIN= topical treatment, not absorbed in GI
5) AMPHOTERICIN= cidal
NYSTATIN= static except at high levels

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II. INHIBITION OF CM SYNTHESIS

* AZOLE *

2) FLUCONAZOLE

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C/S: STATIC

TARGET:

MECHANISM:
- SYSTEMIC: can use this to treat candidas and other systemic mycoses important for AIDS patients

1) given only orally, BUT it's HEPATOTOXIC
2) inhibits ergosterols by inhibiting cyp 450 because hyphae synthesis inhibited by fungi are more easily phagocytosed by PMN's and macs

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III. CELL WALL SYNTHESIS INHIBITION

* ECHINOCANDINS *

3) CASPOFUNGI

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C/S:

TARGET:

MECHANISM:
- a new class of anti- fungals
- no glucan synthesis
- no 1, 3-B-D glucan

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IV. ANTIMETABOLITE

4. FLUCYSTOSINE

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C/S: cidal/ static

TARGET:

MECHANISM:
- only available in antimicrobial with antifungal activity
- it inhibits fungal ps by replacing uracil with 5- flurouracil in fungal RNA