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Micro block 1 > 09 Antibacterial- protein synthesis inhibitors > Flashcards

09 Antibacterial- protein synthesis inhibitors Flashcards

1
Q

Protein Synthesis 30s subunit Inhibitors

A

Protein Synthesis 30s subunit Inhibitors

  • *A**minoglycosides (given IM or IV)
  • *T**etracyclines

remember AT

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2
Q

Protein Synthesis 50s subunit Inhibitors

A

Protein Synthesis 50s subunit Inhibitors

  • *C**hloramphenicol
  • *E**rythromycin (Macrolides)
  • *L**inezolid
  • *L**incosamides (Clindamycin)
  • *S**treptogramin

(CELLS)

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3
Q

what are Aminoglycosides? examples of drugs.

A

Aminoglycosides (bactericidal)

-Aminoglycosides are bactericidal antibiotics that bind to the 30S subunit of ribosome and inhibit bacterial protein synthesis.

Gentamicin***
Neomycin***
Amikacin***
Tobramycin
Streptomycin***
Kanamycin
Netilmicin
“GNATS KaNot kill anaerobes”

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4
Q

Aminoglycosides mode of action

A

MOA:

  • The aminoglycosides are bactericidal antibiotics that bind to the 30S subunit of ribosome and inhibit bacterial protein synthesis.
    • **Inhibit initiation complex* **of peptide formation and also
    • Induce misreading of mRNA*
      • **​They cause a breakup of polysomes into nonfunctional monosomes. **
  • Require oxygen for uptake → inactive against anaerobes

**NOTE: remember to add an aminoglycoside to a b-lactam antibiotic when treating serious P. aeruginosa infection. **

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5
Q

Aminoglycosides mode of administration

A

Aminoglycosides mode of administration:

They are poorly absorbed orally and must be used parenterally** (IM or IV) for systemic infection.

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6
Q

Mechanism of Resistance to Aminoglycosides

(not really stressed)

A

Mechanism of Resistance to Aminoglycosides

  • Bacterial transferase enzymes inactivate the drug by:
    • Phosporylation
    • Adenylation
    • Acetylation
  • Impaired entry of aminoglycoside into the cell.
  • The microorganism produces a transferase enzyme or enzymes that inactivate the aminoglycoside
  • The receptor protein on the 30S ribosomal subunit may be deleted or altered as a result of a mutation.
  • Streptococci and enterococci develop resistanance to aminoglycosides by decreasing penetration)
  • Netilmycin and amikacin are resistant to inactivation by bacterial enzymes
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7
Q

Spectrum of aminoglycosides

A

Spectrum of aminoglycosides

All aminoglycosides have

  • good activity against gram-negative aerobic bacilli*****
    • Used for severe gram negative infections
    • Synergistic action with beta lactam antibiotics
  • Lack activity against anaerobes.

Neomycin:

  • For bowel surgery**

Streptomycin:

  • has a more limited* antibiotic spectrum.
  • Used for tuberculosis, plague, brucellosis
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8
Q

Aminoglycosides side effects

A

Aminoglycosides side effects

Aminoglycosides are toxic to kidneys (nephrotoxic)

  • Must measure drug level , blood urea nitrogen and creatinine to avoid toxicity

Toxic to auditory and vestibular

  • portions of the 8th cranial nerve (Ototoxicity)

NOTE:

Cochlear damage: Results in hearing loss. High frequency sound is affected first then low frequency.

Vestibular damage: Headache appears first followed by nausea, vomiting, dizziness, nystagmus (fast, uncontrollable movements of the eyes), vertigo and ataxia.

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9
Q

what is Streptomycin used for? What group of drugs does it belong to? side effects?

A

Streptomycin

Steptomycin is a Aminoglycosides

Uses: Tuberculosis, plague, brucellosis

Side effects: Ototoxic (CN8 damage) and nephrotoxic

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10
Q

Gentamicin and tobramycin

A

Gentamicin and tobramycin

They are Aminoglycosides

Gentamicin and tobramycin are effective against many gram negative infections including pseudomonas

They are the Most widely used aminoglycoside****

Side effect: Nephrotoxic

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11
Q

Amikacin

A

Amikacin

Amikacin is a aminoglycoside

Amikacin is the** Broadest spectrum ***** of aminoglycoside.

Uses of Amikacin:

Amikacins are effective against Many gram negative infection including pseudomonas

Effective against some of the bacteria that are resistant to gentamicin

Side effect: Cochlear toxic agents

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12
Q

Neomycin. what kind of drug is that, what is it used for. How is it administered?

A

Neomycin

Neomycin is a aminoglycoside

Neomycin is used for Preoperative bowel preparation and Hepatic coma

Used orally since it’s not absorbed

Note: After oral administration, the intestinal flora is suppressed or modified and the drug is excreted in the feces.

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13
Q

what are tetracyclines? list the drugs.

A

Tetracyclines

Group of antibiotics with bacteriostatic activity.

They work by Inhibiting protein synthesis by binding to the 30S subunit- Blocking the aminoacyl transfer RNA (tRNA) from entering*** the acceptor site on the mRNA-ribosome complex. This prevents addition of amino acids to the growing peptide .

Classification

  • Tetracycline
  • Doxycycline****
    • is eliminated in stool
    • Can be used for patients with renal impairment
  • Minocycline
  • Demeclocycline*** (effective against siADH)
    • Makes renal tubules refractory to the action of ADH
    • Used in the management of ADH secreting tumors
      • Small cell carcinoma of lung***
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14
Q

Tetracyclines
Spectrum of Action

A

Tetracyclines (acts on 30s subunits)
Spectrum of Action

Broad spectrum antibiotics
Active against

  • Gram positive and Gram negative bacteria including anaerobes.

Active against

  • atypical bacteria such as rickettsiae, chlamydiae, mycoplasma.

Also active against some

  • protozoa.

Tetracycline is drug of choice (DOC) in infections with

  • Mycoplasma pneumoniae, chlamydia, rickettsia, and some spirochetes.
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15
Q

Primary uses of tetracyclines

A

Primary uses of tetracyclines (acts on 30s subunits)

Primary use: Rx of infections caused by:

  • Mycoplasma pneumoniae* (pneumonia),
  • Chlamydia*
  • Rickettsia *** (Rocky moountain spotted fever)
  • Vibrio** (cholera)
  • Borrellia burgorferi (Lyme disease. a spirochete infection)***
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16
Q

Secondary use of tetracyclines

A

Secondary use of tetracyclines (acts on 30s subunits)

Secondary use: alternative drug to penicillin in syphilis***

17
Q

What is Demeclocycline? *** what is it used for?

A

Demeclocycline is a tetracyclin drug (that act on 30s subunit) that makes renal tubules refractory to the action of ADH

Demeclocycline is used in the management of ADH secreting tumors

  • Small cell carcinoma of lung**
18
Q

Tetracyclines
Side effects

A

-Photosensitivity**

  • Enhanced sensitivity to UV rays (skin)

-Brown discoloration of teeth**

  • In fetuses and young children
    • readily bind to calcium deposited in the newly formed bone or teeth.

-Skeletal deformity and growth retardation:**

  • Due to its deposition in the bone.

-Contraindicated (cannot be used anymore)** in pregnant women and children below 14 yrs of age

-GI distress

19
Q

Mechanism of resistance against tetracyclin

A

Mechanism of resistance against tetracyclin

Development of efflux pump** (encoded by plasmids)

  • –Bacteria pump out the drug
20
Q

Chloramphenicol

A

Chloramphenicol (acts on 50s subunit)

  • *-Broad spectrum*** antibiotic (bacteriostatic)
  • Inhibits protein synthesis by binding to 50S ribosomal subunit and
  • Blocking the action of peptidyl transferase**
    • This prevents synthesis of new peptide bonds

-Side effects:

  • Dose dependent bone marrow suppression**
  • Aplastic anemia** (not dose dependent)
  • If used in pregnancy → Causes Grey baby syndrome**.
    • Infants lack glucuronic acid conjugation mechanism for the degradation of chloramphenicol
  • vomiting, gray color(cyanosis), shock.
21
Q

Chloramphenicol uses and side effects

A

Chloramphenicol uses and side effects

Clinically useful activity

  • Meningitis: H. Influenza, S.pneumoniae, N.meningitidis
  • Rocky Mountain Spotted fever (Rickttsia rickettsii)

side effect

  • Bone marrow toxicity limits use to only severe infections
22
Q

what are the Macrolides drug? what are their mechanism of action.

A

Macrolides (act on 50s subunit)

  • *-Erythromycin***
  • New ones include:
  • Azithromycin*
  • Clarithromycin*

-Bind to the 50S subunit

  • Protein synthesis is inhibited because
    • translocation is blocked (“macroslides”)
23
Q

Erythromycin uses and side effect

A

Erythromycin (act on 50s subunit)

Erythromycin is a macrolide that acts on the 50s (subunit)

Uses:

  • Pneumonia caused by Mycoplasma and Leoginella.
  • Infections by gram positive cocci (Streptococci) in penicillin allergic patients

side effects:

  • Generally well tolerated but some diarrhea
24
Q

what is Azithromycin? what are it’s uses

A

what is Azithromycin? what are it’s uses

  • Same as erythromycin
    • Pneumonia caused by Mycoplasma and Leoginella.
    • Infections by gram positive cocci (Streptococci) in penicillin allergic patients
  • …..plus more activity against Chlamydia, Mycobacterium avium complex (MAC) and Toxoplasma
  • longer half life
25
Q

what are Clarithromycin? what are its uses?

A

What are Clarithromycin (macrolides that act on 50s subunits)?

Clarithromycin is used clinically against

  • URT (upper respiratory tract) and lower respiratory tract infections. Atypical pneumonia
  • H.Pylori treatment in recurrent peptic ulcer.
  • prophylaxis (action taken to prevent disease) of Mycobacterium avium complex (MAC)
  • longer half-life
26
Q

what is Clindamycin? what is its uses, mode of action and mechanism of resistance?

A

Clindamycin (a lincoamides)

  • Clindamycin mode of action is
    • Blocks peptide transfer (translocation) at 50s ribosomal unit**.
  • Uses:
    • Infections caused by anaerobic bacteria*****
      • Gram positive anaerobe: Clostridium perfringens
      • Gram negative anaerobe: Bacteroides fragilis
    • For prophylaxis (treament to prevent disease) of infective endocarditis in patients with valve diseases
    • Active against Pneumocystis carinii and Toxoplasma gondii
  • Mechanism of resistance:
    • methylation of binding site** on the 50S ribosomal subunit

NOTE: DO NOT CONFUSE WITH CLARITHROMYCIN

27
Q

Clindamycin’s side effect

A

Clindamycin ( is a Lincosamide) side effect

  • Most important side effect:
    • Suppression of normal GI flora
      • Overgrowth of C. difficle
      • Superinfection results in development of Pseudomembranous colitis (because of C.difficile)****
        • Watery diarrhea, abdominal pain etc.
        • Rx: Vancomycin / Metronidazole

**Note: **symptoms includes:

  • GI irritation
  • Skin rashes
  • Neutropenia
  • Superinfection (pseudomembranous colitis due to C. difficile)
28
Q

What is Linezolid? What is the Mode of action, uses and side effects?

A

Linezolid ( part of the Oxazolidinone group of drugs)

  • MOA:
    • Binds to the 23S ribosomal RNA in the 50S subunit**
    • Inhibits protein synthesis
  • Useful for the treatment of:
    • Vancomycin resistant enterococci (VRE)
    • Methicillin resistant S.aureus (MRSA) and S.epidermidis (MRSE)
    • Penicillin resistant pneumococci
  • Side effects:
    • thrombocytopenia and neutropenia
      • especially in immunocompromised patients
29
Q

Streptogramins include what drug? what it is use and side effect?

A

​Streptogramins (ex. Quinipristin-dalfopristin combination)

Streptogramins are effective in the treatment of vancomycin-resistant Staphylococcus aureus (VRSA) and vancomycin-resistant Enterococcus (VRE)

Quinipristin-dalfopristin combination

  • Acts by inhibiting the tRNA synthetase*
  • Clinical uses:
    • MRSA (Methicillin resistant Staph.aureus)
    • VRSA & VRE
  • Side effects:
    • Arthralgia, myalgias

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