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Micro block 1 > 08 Antibacterial- cell wall synthesis inhibitors > Flashcards

08 Antibacterial- cell wall synthesis inhibitors Flashcards

1
Q

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Bactericidal Drugs<!--EndFragment-->

what they do and example of these drugs

A

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Bactericidal Drugs<!--EndFragment-->

Cause death of the microorganism

Eg:

Penicillins

Aminoglycosides

Cephalosporins

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2
Q

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Bacteriostatic Drugs and what they do

A

Bacteriostatic Drugs and what they do

Inhibit the growth of the microorganism

E.g. Sulfonamides, Tetracyclines, Erythromycin

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3
Q

Drugs for Inhibition of cell wall systhesis

A

Inhibition of cell wall systhesis

Penicillins**

Cephalosporins**

Carbapenems

Monobactum

Vancomycin**

Bacitracin

Cycloserine

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4
Q

Drugs for Inhibition of protein synthesis

A

Inhibition of protein synthesis

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Tetracyclines

Macrolides

Chloramphenicol

Aminoglycosides

Streptogramins

Linezolid

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5
Q

Drugs for Inhibition of nucelic acid synthesis

A

Inhibition of nucelic acid synthesis

Fluroquinolones

Rifampin

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6
Q

Drugs for Inhibition of folic acid synthesis

A

Inhibition of folic acid synthesis

Sulfonamides

Trimethoprim

Pyrimethamine

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7
Q

Beta lactam antibiotics

A

Beta lactam antibiotics

  1. Penicillins **
  2. Cephalosporins**
  3. Carbapenems
  4. Monobactum
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8
Q

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Cross linking is catalyzed by what bacterial enzymes? mention all known names

A

Cross linking is catalyzed by what bacterial enzymes?

Transpeptidases** AKA penicillin-binding proteins (PBPs)**** because they can be bound by beta-lactam antibiotics (e.g. penicillin)

  • they bind to and inactivate penicillin binding proteins (PBP) e.g. transpeptidase***
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9
Q

What are Penicillinase? It acts on what to confer resistance? example?

A

Penicillinase act on what to confer resistance?

Penicillinase are enzymes produced by the bacteria

They act on the four-member nitrogen-containing b-lactam ring** of b-lactam drugs.

Eg: Penicillinases** (b-lactamases) break the betalactam ring

  • eg. Staphylococci
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10
Q

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Side effects of Penicillins<!--EndFragment-->

A

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Side effects of Penicillins<!--EndFragment-->

Hypersensitivity reactions – rare

  • Skin rashes
  • Acute anaphylactic shock***

Alter bacterial flora of the gut***

  • GI disturbances (esp broad spectrum) -> Clostridium difficle overgrowth

Cross-sensitivity is possible***

  • (allergic to one may also be allergic to others)
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11
Q

Types of penicillins

A

Types of penicillins

  • Narrow Spectrum penicillin (Penicillinase susceptible)
  • Narrow Spectrum (Penicillinase resistant) penicillins
  • Broad spectrum (Penicillinase susceptible) penicillins
  • Extended spectrum or antipseudomonal
  • Beta-lactam with beta lactamase inhibitor
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12
Q

Broad spectrum penicillins

A

Broad spectrum
(Penicillinase susceptible) penicillins

Includes: Ampicillin**, amoxicillin**
Spectrum of activity:

  • Activity against gram positive cocci
  • Active against some gram negative rods**

Uses:

  • Infections due to Haemophilus influenzae, E. coli Listeria monocytogenes, Proteus mirabilis,, Salmonella, Shigella
  • (Coverage: ampicillin/amoxicillin HELPSS kill enterococci)

note: Activity enhanced if used in combination with beta lactamase inhibitors (clavulanic acid, sulbactum)- widens the spectrum

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13
Q

What is Amoxicillin? What is it used for?

A

Amoxicillin

  • Amoxicillin is a broad spectrum penicillins that is Penicillinase susceptible.
  • It’s effective against gram positive cocci and **some **gram negative rods**

Amoxicillin is also use to:

  • prevent bacterial endocarditis* before major surgical procedures
  • used in H.pylori infection (peptic ulcers)

Main uses of Amoxicillin and other broad spectrum are:

Infections due to Haemophilus influenzae, E. coli Listeria monocytogenes, Proteus mirabilis, Salmonella, Shigella

(Coverage: ampicillin/amoxicillin **HELPSS **kill enterococci)

Note: Activity enhanced if used in combination with beta lactamase inhibitors (clavulanic acid, sulbactum)- widens the spectrum

Toxicity:

Hypersensitivity reactions
Pseudomembranous colitis****

Note: broad spectrum penicillins Includes: Ampicillin**, amoxicillin**

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14
Q

Extended spectrum or antipseudomonal penicillin

A

Extended spectrum or antipseudomonal penicillin

Includes:
Ticarcillin, piperacillin***, azlocillin

Mechanism:

  • Same as penicillin, extended spectrum

Spectrum:

  • Gram –ve rods including
    • Pseudomonas aeruginosa***

Penicillinase sensitive→ use with Beta lactamase inhibitors.

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15
Q

Beta lactamase inhibitors

A

Beta lactamase inhibitors

Include:*****
Clavulanic Acid
Sulbactum
Tazobactum
= (CAST)

Often added to penicillin antibiotics to protect the antibiotic from destruction by beta lactamase (penicillinase).

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16
Q

penicillins with beta lactamase inhibitor combinations

A

penicillins with beta lactamase inhibitor combinations

  • Piperacillin + tazobactum**
  • Ampicillin + sulbactum
  • Amoxicillin + clavulanate
  • Ticracillin+ clavulanate

Spectrum of activity:

  • Activity similar to natural beta lactams, plus, improved activity against beta lactamase producing staphylococci and selected gram negative rods.
  • Piperacillin + tazobactum is the most active**
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17
Q

Prophylactic uses of Penicillins

A

Prophylactic (a medicine or course of action used to prevent disease) uses of Penicillins

Rheumatic fever- is an inflammatory disease that may develop after an infection with group A Streptococcus bacteria (such as strep throat or scarlet fever)

  • Benzathine penicillin

Gonorrhoea & Syphillis in sexual partner

  • Benzathine penicillin

Bacterial endocarditis prophylaxis

  • Amoxicillin or ampicillin
  • In patients with prosthetic heart valves, cyanotic heart disease, previous diagnosis of endocarditis- who are planning to undergo dental or respiratory tract or genitourinary or gastrointestinal procedures
18
Q

Cephalosporins

A

Cephalosporins

Cephalosporins

  • Cephalosporins are beta lactam antibiotics***
  • Cephalosporins inhibits cell wall synthesis but are less susceptible to penicillinases.
  • Cephalosporins are Bactericidal
  • Cephalosporins Have the same MOA (mechanism of action) as penicillins, however they have wider* antibacterial spectrum
  • Are resistant* to many beta lactamases
  • have longer half lives*

Resistance to cephalosporins is due to :

  • Production of Beta-lactamases* (cephalosporinases)
19
Q

1st generation cephalosporins

A

1st generation cephalosporins

Includes:

  • Cephalexin (oral), cefazolin (parenteral)

Spectrum of activity:

  • Active against Gram positive cocci
  • Some gram negative activity
    • Proteus, E.coli, Klebsiella pneumoniae
    • = PEcK**

Use:

  • Cefazolin used prior to surgery to prevent S.aureus wound infections**
20
Q

2nd generation Cephalosporins

A

2nd generation Cephalosporins

Includes:

  • Cefoxitin*, Cefuroxime* ,Cefaclor,

Spectrum of activity:

  • Improved gram negative activity***
    • Haemophilus influenza, Enterobacter, Neisseria, Proteus, E.coli, Klebsiella pneumoniae, Serratia (HEN PEcKS) ***

Active against gram positive cocci and some anaerobe e.g. Bacteroides fragilis*
Uses:
Cefoxitin, cefotetan- Bacteroids fragilis*

Cefuroxime, cefaclor, cefamandole – H.influenza*

Note:

Except Cefuroxime others do NOT enter CSF

21
Q

3rd generation cephalosporins

A

3rd generation cephalosporins

Includes:

  • Ceftriaxone(IM)**, Cefotaxime**, Cefixime (oral) ,Ceftazidime and cefoperazone,

Spectrum:

  • Active against gram positive bacteria*
  • Improved gram negative activity* to include Pseudomonas
  • Can cross BBB** (except Cefoperazone & Cefixime)

Clinical uses:

  • Serious gram negative infections- not responding to other beta lactams
  • Bacterial Meningitis*: Ceftriaxone*****
  • Acute cholecystitis*: Cefotaxime, Ceftriaxone
  • Pseudomonas infections*: Ceftazidime***
  • Gonorrhoea*: Ceftriaxone**** (parenteral) & Cefixime
  • Salmonella typhi infections*: Ceftriaxone, cefaperazone
22
Q

4th generation cephalosporins

A

4th generation cephalosporins

Includes:

  • Cefepime(IV)**, cefpirome
  • Resistant to inactivation by beta lactamases*
  • Excellent penetration into gram negative bacteria – increased activity against pseudomonas aeruginosa*
  • Wider spectrum than 3rd generation (both Gram positive & negative)
  • 4th generaion cephalosporins are Reserve drugs*** and to be used only if the other drugs fail to produce any response.
23
Q

Cephalosporins
Side effects

A

Cephalosporins
Side effects

Hypersensitivity reactions- rashes, fever

Cross-reaction between penicillins and cephalosporins

  • History of anaphylaxis to penicillin is a contraindication for cephalosporin

Superinfection- diarrhea

note: If given with aminoglycosides- Increased chances of nephrotoxicity

Cefamandole, Cefoperazone & Cefotetan contain methylthiotetrazole group (MTT group) may cause dusulfiram like reactions with ethanol

Vitamin K deficiency causing hypoprothrombinemia and bleeding disorder

24
Q

Organisms not covered by cephalosporins:

A

Organisms not covered by cephalosporins are LAME!

= LAME

  • *L**isteria monocytogenes
  • *A**typical bacteria (Chlamydia, Mycoplasma)
  • *M**RSA (exception; ceftaroline coveres MRSA)
  • *E**nterococci
25
Q

Other beta lactam antibiotics

A

Other beta lactam antibiotics Include:

–Carbapenems like Imipenem***, Meropenem, Ertapenem

–Monobactams like Aztreonam**

26
Q

Carbapenems

A

Carbapenems (one of the other beta lactam antibiotics)

Include:
Imipenem***, Meropenem, Ertapenem

Are broad spectrum* antibiotics

Beta lactamases resistant**

Always used with cislastatin (inhibitor of renal dehydropeptidase I) to decrease inactivation of drug in renal tubules

Virtually active against all groups of organisms

Wide activity against Gram positive cocci, Gram negative rods and anaerobes

**Drug of choice in the Rx of Enterobacter infections

Reserve drugs**: used only when other antibiotics not effective

27
Q

Monobactams

A

Monobactams (one of the other beta lactam antibiotics)

Includes:

  • **Aztreonam** **
  • Resistant to beta lactamases
  • No cross allerginenicity with penicillins
  • Narrow* spectrum antibiotic
  • Only active against Gram negative* rods
  • Anaerobic and gram positive bacteria are resistant
  • *-Can be given to patients who are allergic to penicillin*****
28
Q

Vancomycin

A

Vancomycin (classified as the Other Cell wall synthesis inhibitors)

  • Vancomycin is a bactericidal glycoprotein***
  • Mechanism of action:***
  • Binds to D-Ala-D-Ala terminal of peptidoglycan side chain. this leads to Inhibition of cross linking** of the peptidoglycan chains.

-Narrow spectrum

-Used for serious infections* caused by drug-resistant Gram positive organisms especially:

  • MRSA**,
  • Penicillin resistant pneumococci and
  • Clostridium difficile**

**Oral vancomycin is given for refractory C. difficile pseudomembranous colitis

  • Initial treatment of choice for pseudomembranous colitis is Metronidazole

____________________________

notes:

  • Acts by binding to D-Ala-D-Ala terminal of the nascent peptidoglycan pentapeptide side chain
  • This leads to inhibition of transglycosilation
  • This in turn prevents the peptidoglycan chain elongation
  • All this leads to inhibition of cross linking of the peptidoglycan chains
29
Q

Mechanism of Resistance to Vancomycin ***

A

Mechanism of Resistance ***

  • Occurs in bacteria via amino acid modification of D-ala D-ala to D-ala D-lac
  • decreased affinity of vancomycin for the binding site
  • Occurs in strains of enterococci and staphylococci (VRE and VRSA)
30
Q

Vancomycin
Adverse Effects

A

Vancomycin
Adverse Effects

-Nephrotoxicity, Ototoxicity, Thrombophlebitis

  • remember noooo, NOT vancomycin .vancomycin is a red mon bad mon…. because of its many adverse effects.

-Red man syndrome ***

  • because of release of histamine (flushing, redness of face, hypotension),
  • this can be prevented by pre-treatment with **antihistamines. **
  • resolves spontaneously after discontinuation
31
Q

Other cell wall synthesis inhibitors

A

Other cell wall synthesis inhibitors

Bacitracin

  • Very nephrotoxic
  • Acts by inhibiting cell wall synthesis
  • Used topically for its antibacterial property

**Cycloserine **

  • inhibits many gram-positive and gram-negative organisms
  • Used almost exclusively to treat tuberculosis*** caused by strains of M tuberculosis resistant to first-line agents
32
Q

Rx of syphilis

A

Rx of syphilis is penecillin G*

33
Q

Rx of gonorrhea

A

Rx of gonorrhea is ceftriaxone*

34
Q

Rx of MRSA

A

Rx of MRSA is vancomycin*

35
Q

Rx of C. difficile

A

Rx of C. difficile - metronidazole* or vancomycin*

36
Q

Rx of acute ottitis media

A

Rx of acute ottitis media (inflammation of the middle ear) – ceftriaxone single dose*

37
Q

Rx of Meningitis

A

Rx of Meningitis – ceftriaxone, Cefotaxime*

38
Q

Rx of Pseudomonas

A

Rx of Pseudomonas – Cefoperazone*, Ceftazidime*, piperacillin***

39
Q

Cefazolin is used for?

A

Cefazolin used prior to surgery to prevent S.aureus wound infections**

40
Q

**Drug of choice in the Rx of Enterobacter infections

A

**Drug of choice in the Rx of Enterobacter infections (gram-negative facultative anaerobe. rod-shaped)

Carbapenems drugs (includes imipenem)

Note: carbapenems are always used with cislastatin to decrease inactivation of carbapenems in renal tubule.

Micro block 1 (11 decks)

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