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Anti bacterial drugs Flashcards

1
Q

examples in each class and the uses of antibacterial drugs that inhibit cell wall synthesis

A

β-Lactams
• Penicillins
• Cephalosporins
• Carbapenems, monobactams

Other
a. Peptides
Glycopeptides (vancomycin, teicoplanin)
b. Fosfomycin

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2
Q

True or false: cell wall synthesis inhibitors are selectively toxic, why?

A

True because mammalian cells do not have cell membranes

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3
Q

What is peptidoglycan?

A

An outer cell membrane whereby its basic building blocks are synthesis in the bacterial cytoplasm and transported through the cell memebrane

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4
Q

What is peptidoglycan?

A

A unique structural element of the cell wall, its basic building blocks are synthesis in the bacterial cytoplasm and transported through the cell membrane. It consists of amino acid sugars, alternating residues of N-acetyl glucosamine, and acetyl muramic acid.

An enzyme called transpeptidase cross-link the amino acid sugars

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5
Q

Discuss the mechanism of action of beta-lactam

A

beta lactams are bactericidal.
When a bacteria is in a growth and replication phase ,the beta lactam inhibits the transpeptidase thus disrupting the cell wall ( peptidoglycan ) synthesis. The cell wall defects resulting in swelling of the bacteria eventually rapturing

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6
Q

What is the difference between the mechanism of action between beta lactam and vancomycin

A

beta lactam drugs interfere with formation of the peptide side chain between adjacent strands of the peptidoglycan by inhibiting penicillin- binding proteins whereas vancomycin binds to the amino acid side chain of N-acetyle muramic acid molecules ,interfering with peptidoglycan molecules

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7
Q

What are the features that grants bacteria resistance ?

A
  1. cell wall
  2. bacteria not growing
  3. Altered penicillin binding proteins
  4. Permeability barrier (gram negative bacteria )
  5. Some bacteria lack autolysins
  6. Mutations can also reduces or eliminate activity
  7. beta lactamase production
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8
Q

beta-lactamases

A

These are enzymes that can destroy penicillin but they can be destroyed by beat lactam

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9
Q

give examples of natural penicillins

A

Penicillin G (Benzyl penicillin) and Penicillin V ( Phenoxy methyl penicillin) .

They have a narrow spectrum and are beta Lactamase sensitive

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10
Q

Which conditions can be treated by Penicillin G( benzyl Penicillin )

A
  1. Tonsillitis : Gram pos cocci and anaerobic (streptococcus pyogens)
  2. Pneumonia : Pneumococci
    3.Meningitis : Gram neg cocci eg Neisseria meningitidis
    4.Gonorrhea : Neisseria gonorrhoeae
    5.Tetanus ,gangrene : Gram positive ,rod bacteria eg clostridium
    6.Oropharyngial infections (bacteriodes fragilis)
    7.Syphilis ; Treponema
    Abscesses ; Actinomyces
    9.Enterococci less susceptible ass aminoglycoside
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11
Q

List the uses of prophylaxis

A
  1. Streptococcal infections
  2. Pheumatic fever
  3. Surgical or dental procedures on patients with valvular heart conditions

Penicillin G (benzyl penicillin

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12
Q

Discusses the uses of Penicillin V (phenoxymethly penicillin )

A

*Penicillin V is 2 to 4 less active that penicillin G
*Used mostly for the treatment of less serious infections eg streptococcal tonsillitis or pharyngitis
*Currently not available in SA
or
It can be used as a follow up anti biotic treatments after serious infections responded well to parenteral treatment

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13
Q

list the penicillins that are resistant to beta-lactamase breakdown and their uses

A
  1. Floxacillin
  2. Flucloxacillin
  3. Methicillin ( not available in SA)

Uses:

  • Slightly less active than penicillin G
  • They are used for the treatment of mild beta lactamase positive staphylococcal infections
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14
Q

Broad spectrum : Aminopenicillin

A

Characteristics : Active against many gram neg and pos bacteria

The amino side chain is hydrophilic and thus penetrate the gram neg outer membrane through porins

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15
Q

which aminopenicillin is sensitive to beta-lactamase

A

amoxicillin and ampicillin

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16
Q

which aminopenicillin is resistant to beta-lactamase

A

Augmentin ( amoxicilin and clavulanic acid(coamoxiclav)

17
Q

which aminopenicillin has an extended spectrum

A

Ampicillin and cloxacillin

18
Q

Uses of Ampicillin

A

Used mostly in gram pos bacteria and H.Influenza and aminopenicillin that has a extended spectrum)

sensitive to beta lactamase

19
Q

Clinical characteristics of amoxicillin

A
  • Gram pos spectrum ,similar to penicillin G ,activity against enterococci and listeria
  • Gram neg , spectrum H.Influenza ,Ecoli ,Proteus Mirabilis ,salmonella and shigella .

sensitive to beta lactamase

20
Q

Clinical uses of Amoxicillin

A
  1. For otitis ,sinusitis ,lower RTI
  2. Soft tissue infection
  3. Cholecystitis ,GIT infections including thyroid
  4. Urinary tract infection ( possibility of resistance developing)
  5. Prophylaxis to prevent infective endocarditis
21
Q

What is the function is clavulanic acid ?

A

clavulanic acid has no antibiotic activity ,it binds covalently near or inthe active of the beat lactamase enzyme.

Clavulanic ACID IN COMBINATION WITH AMOXICILLIN (AUGMENTIN) PROTECTS THE ANTIBIOTIC AGAINST DEGRADATION BY BETA LACTAMASE

22
Q

List the antipseudomonal penicillins that fall under the extended spectrum antibiotics and are beta lactamase inhibitors

A

piperacillin and tazobactam

23
Q

Where are these drugs excreted

A

metabolism is limited and they are excreted mainly unaltered vis the kidneys

24
Q

Where are these drugs excreted

A

metabolism is limited and they are excreted mainly unaltered via the kidneys

25
Q

Extend the action of penicillin G:

A

Higher dosages, plasma level above the MIC
• Probenecid
• Depot formulation via intramuscular injection
(procaine and benzathine)

26
Q

Penicillins

Side-effects

A
  1. Hypersensitivity reactions
    (skin rashes → anaphylactic shock)
  2. Haematological effects (↓ white blood cells)
  3. Bleeding → penicillin G & Piperacillin → ↓
    platelet aggregation
  4. Neurotoxic effects → high doses of penicillin G
  5. Flucloxacillin → cholestatic hepatitis
  6. Co-amoxiclav
    → superinfections (yeast and
    pseudomembranous colitis)
    → Reduced efficacy of combined oral
    contraceptive pill
    Hepatitis and cholestatic jaundice → clavulanic
    acid
  7. Infectious mononucleosis (amoxicillin)
  8. Co-amoxiclav→ caution during lactation →
    excreted in mothers milk
  9. Formulations as sodium or potassium salts in
    high doses → use with care in patients with
    cardiac and renal disease (fluid retention &
    hypokalaemia, hypernatraemia)
27
Q

Cautions/Contraindications

A
  1. Elderly
  2. Neonates (extended dose intervals)
  3. C/I when allergic
  4. Flucloxacillin - porphyria
28
Q

Drug interactions of probenecid

A

Must not combine aminoglycosides and penicillins

in same syringe or infusion, or same IV line

29
Q

Broad spectrum penicillins:

A

Allopuranol (skin rash)

– Combined oral contraceptive pill

anti bacterial drugs (7 decks)

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