Cell Wall Synthesis Inhibitors Flashcards
Formation of cell wall predecessor
NAM NAG complex - GAG
1. NAG + PEP using EPT Enolpyruvate transferase
2. NAM-NAG complex-GAG
Peptide chains ⛓:
1. L-alanine to D-form by alanine racemase
2. To alanine library chain by alanine ligase
3. Glycine added to it to form a T-shaped peptide
Cell wall formation from cell wall precursor
- Both the precursors joint in cytoplasm
- It is transported outside the cell membrane by lipid transporter (bactoprenol)
- It is polymerized by transpeptidase
Drugs acting on cell wall synthesis
- Fosfomycin and fosmidomycin 🅱️ EPT
- Cycloserine: 🅱️ alanine racemase, alanine ligase
- Bacitracin: 🅱️ lipids transporter
- Glycopeptides: vancomycin
🅱️ D-alanine from forming cross-links - β-lactams: 🅱️ transpeptidase
Penicillins, cephalosporins, monobactams, carbapenems
Fosfomycin and fosfodomycin
mechanism and pharmacokinetics
Analogues of PEP ➡️ competitive 🅱️ of EPT
Pharmacokinetics:
• excreted unchanged in urine ➡️ UTI 3gm single dose
• safe in 🤰
Fosfomycin and fosfodomycin
spectrum
Limited spectrum
G-6-P transporter required for transportation into cell ➡️ only gram ➖ve bacteria
Eg., E. coli, klebsiella, serratia
Cycloserine
• D-alanine analogue ➡️ 🅱️ alanine racemase, ligase ➡️ cell wall synthesis 🅱️
• Gram ➖ve bacteria
• 2nd line drug for TB
• S/E: neuropsychiatric
Seizure, psychosis, peripheral neuropathy
Bacitracin
🅱️ lipids transporter ➡️ cell wall unit transport 🅱️
S/E:
nephrotoxic and bone marrow suppression ➡️ no systemic use
Topical:
• skin infections
• staph nasal carriers (MRSA)
DoC topical mupirocin
Local: GIT
• pseudomembranous enterocolitis
• VRE (vancomycin resistant enterococcus)
Glycopeptides
effects of its size
Large in size ➡️ 🔽 oral absorption
Spectrum:
Gram ➕ve bacteria
In gram -ve bacteria, porins allow only small size molecules and water soluble particles to pas
Vancomycin
IV route: DoC
1. MRSA
2. Enterococcus faecium
3. Ampicillin resistant enterococcus faecalis
Oral route: DoC
Pseudomrmbranous enterocolitis
• if not responding: fidaxomycin, rifaximin
S/E:
1. 🔼 release of histamine: red neck/man syndrome
2. Nephrotoxic
3. Ototoxic
Recent advances for prophylaxis of pseudomembranous enterocolitis
- Bezlotoxumab
Anticlostridium difficile toxin-B antibody - Actozumab:
Anticlostridium difficile toxin-A antibody
Other glycopeptide drugs
- Teicoplanin
- Dalbavancin: long acting
- Telavancin and Oritavancin:
Disrupts cell membrane ➡️ 🔼bactericidal
Use: only for SSTI by MRSA
Narrow spectrum penicillins
Penicillin-G • lipid soluble • active day 1. G ➕ve 2. Some G ➖ve bacteria (meningococcus) Structure: R group present
Broad spectrum
• Amidase enzyme ➡️ breaks side chain R
• functional group FG added in place of side chain R
➡️ ionised and water soluble
➡️ active against G ➖ve also
Classification of broad spectrum penicillins
1. Amino (+ve): orally • amoxicillin, ampicillin 2. Carboxy (-ve): parenteral • carbenicillin, ticaricillin 3. Ureido (+ve, -ve): parenteral Max active against G➖ve organism Piperacillin, Azlocillin, Mazlocillin The last two groups are active against pseudomonas
Amoxicillin
uses
- Diverticulitis
- Cellulitis
- Ludwig’s angina
- Vincent’s angina
- UTI (safe in 🤰)
Ampicillin
uses
DoC for:
- Meningitis by listeria
- H influenza: pneumonia, otitis
- Enterococcus faecalis
- Shigella infections
Uses of ureidopenicillin like piperacillin, mezlocillin
Active against klebsiella and enterococcus
Penicillin G
IV route (aqueous) (IM route ➡️ injection site reaction) Pharmacokinetics: 1. Poor oral absorption: Acid labile unlike acid stable P. V 2. Rapid tubular secretions: P-gp pumps ➡️ Very short acting (long acting can be made)
Long acting penicillin
- P-gp
Probenecid penicillin G
IM route (not IV, toxicity)
Measured in IU, 1mg = 1600 IU - 🔼 H2O solubility:
Given IM:
• procaine penicillin-G: no pain at injection site (local anesthetic)
• benzathine penicillin-G: longest acting (28 days)
DoC: prophylaxis of rheumatic fever (monthly)
Penicillin uses
- Syphilis
- Streptococcus infection
- Gas gangrene
- Yaws
- Leptospirosis
- Rat bite fever
Benzathine penicillin G
2.4 million IU once
• 1° syphilis
• 2° syphilis
S/E: Jarisch Herxheimer reaction (hypersensitivity reaction)
🤒, arthralgia, myalgia, worsening of cutaneous lesion
• Early latent syphilis
Benzathine penicillin G
2.4 million IU 3 doses once/week
- Tertiary syphilis (without CNS involvement)
- CNS involvement
- Late latent
Neurosyphilis
DoC
Aqueous penicillin G
18-24 million IU
Continuous IV infusion (10-14 days)
Mechanism of resistance of penicillin in gram ➖ve bacteria
- Decreased porin production
Eg., pseudomonas - Drug efflux
Eg., pseudomonas, E. coli, gonococcus
Mechanism of resistance of penicillin in gram ➖ve & gram ➕ve bacteria
- Altered transpeptidase (protein binding protein)
Eg., Staphylococcus ➡️ MRSA ➡️ mec A gene - β-lactamase production: Ambler production
Ambler classification of β-lactamase production
Class A: ESBL enzymes
DoC carbapenems
• penicillinase
• cephalosporinase
• monobactams
Class B: all enzymes except monobactamase
Class C: cephalosporinase
Class D: cloxacillinase
NDM-1 (New Delhi metalo-1) β lactamase breaks
β lactams/fluoroquinlones, macrolides, Chloramphenicol
Rx: Tigecycline, colistin
β lactamase inhibitors
- Clavulanic acid: with amoxicillin
- Sulbactam: with ampicillin
Rx: acinetobacter - Tazobactam: piperacillin
- Avibactam: with ceftazidime
- Vaborbact: with meropenem
- Relebactam: with imipenem + cilastatin
Oral penicillinase resistant penicillins
- Cloxacillin: DoC mastitis
- Dicloxacillin:
Most active PRP‘S agonist Staph - Oxacillin: hepatotoxic
Parental drugs
1. Nafcillin: Most active PRP (other microbes) S/E: neutropenia 2. Methicillin: S/E: interstitial nephritis
Cephalosporins
spectrum according to generation
1st generation: • Most G➕, some G➖ • anaerobes except bacteriodes 2nd generation: • both G ➕&➖ • anaerobes and bacteroides 3rd gen: only G➖ 4th gen: • both G➕&➖ • pseudomonas, enterobacter 5th gen: • both G➕&➖ • Staph, Strept, MRSA
First generation cephalosporins
examples
Cefadroxil
Cefradin
Cephalexin
Cefazolin-IV others are oral
Cefazolin IV uses
(1st gen cephalosporin)
- Staph infections
- Strept infections
- DoC: surgical prophylaxis;
• 1 hr before incision
• 24 hr after surgery
Uses of cefadroxil and cephalexin
(1st gen cephalosporins)
UTI
active against E. coli, klebsiella
Well concentrated in urine
Second generation cephalosporins
examples
Follow Maur taxi par Fa cefaclor Lo loracarbef Ma cefamandole Ur cefuroxime Ta cefotetan Xi cefoxitin Par cefprozil Follow oral par Maur IV/IM
Uses of ‘follow maur’ of second generation cephalosporins
Not active against bacteroides Uses: 1. Pneumonia 🫁 2. Otitis 👂 3. Surgical prophylaxis 4. Sinusitis
Uses of cefotetan and cefoxitin
Cefotetan: • most active against anaerobes • prophylaxis of anaerobic infection ➡️ Used in colorectal surgeries Cefoxitin: • 2nd most active against anaerobes • use: Rx off PID, lung abscess
Third generation cephalosporins
Delhi PMT Xam Delhi: orally Cefdinir Cefditoren Cefpodoxime P. Cefoperazone M. Moxalactam T: IV/IM Ceftriaxone (longest acting) Ceftizoxime Cefotaxime (shortest acting) Ceftazidime Xam: Cefixime - orally
Ceftriaxone
uses
DoC: 1. Gonorrhea: current ToC: ceftriaxone + Azithromycin/doxycycline 2. E. coli infections 3. Klebsiella 4. Providencia 5. Typhoid (oral DoC cefixime) 6. Meningitis caused by: except listeria • H influenza • meningococcus • empirical 7. Osteomyelitis
Ceftazidime
uses
- DoC for pseudomonas, add aminoglycoside
- Melioidosis
- Febrile neutropenia
Ceftolozane
Derivative of ceftazidine (3rd generation cephalosporin) Used: 1. against pseudomonas With Tazobactum against: 2. Complicated abdominal infections 3. UTI