How Anti Microbials inhibit the cell walls of bacteria ? Review of pharmacology from lipincott.

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 Anti – microbial drug selectively interfere with synthesis of bacterial cell wall 

Anti Microbial , anti biotic, penicillin, cephalosporin, carbapenum, vancomycin ,


Pencillins

MOA: 

interfere with last step of Bacterial cell wall synthesis (Transpeptidation/Cross-linkage)….result in exposure of Alteration in Osmotically memb…Cell lysis occur … either though Osmotic pressure or by Autolysin….Pencillin effective only against rapid growing bacteria 

Pencillin-binding Protein

 1. PBP are bacterial enzymes involved in synthesis of cell wall 

 2. PBP involved in maintenance of morphological feature… Pencillin also cause changes in morphological feature 

Inhibition of Transpeptidase

  • PBP catalyze cross-linkage b/w Peptidoglycan chain…. 
  • Pencillin inhibit this Transpeptidase-Catalyzed reaction…. the cross-linkage formation essential for integrity of cell wall….
  • As a result” Park Nucleotide” UDP-acetylmuramyl-Ala-D-Gin-L-lys-D-Ala-D-Ala accumulation 

Production of Autolysin

  •  Gram+Ve cocci produce degradative enzyme “Autolysin” for remodeling of cell wall…Pencillin increase Autolysin process 
  • 6-Aminopencillanic acid contain β-lactam ring conataining C-N amide bond 
  • Pencillin obtained from Pencillium chrysogenum, 
  • Pencillin G (Benzyl pencillin), & Pencillin V are Sucepetible to β-lactamase 
  • Antistaphylococcal are Pencillinase-resistant protein,treat MSSA(methicillin-sensitive S.aureus) 
  • Ampicillin & Amoxicillin= effective against Gram-Ve bacilli….Ampicillin DOC in Listeria Monocytogenes & Enterococci…inactivated by Plasmid mediated-Pencillinase 
  • Antipseudomonal pencillin= activity against Respiratory infection…

T.E:

  •  used in Gonorrhea (Neisseria gonorrhea), Syphilis (Treponema pallidum),
  • Pneumococcal Pneumonia (S.pneumonia)

Resistance: 

1.hydrolyze by β-lactamase

 2.↓ permeability

 3.altered PBP

P.K

orally, Depot form (I/M) only Amoxicillin completely Absorbed….Abs ↓ by food…

excreted by Organic acid secretary sys…

Probenecid compete with it

S.E:

Hypersensitivity; due to Pencilloic acid react with Hapten….cause Maculopapular rash, Angioedema, Diarrhea, Pseudomembranous colitis, Methicllin cause Nephritis, Neurotoxicity, Seizure, ↓ Coagulation, Cytopenia(CBC test), cation toxicity of Na+ or K+

Cephalosporins

Anti-bacterial spectrum= ineffective against MRSA &C.difficile

First Generation

resistant to Staphylococcal Pencillinase, show activity for PEcK (Protius mirabilus, E.coli, Klebsiella pneumonia)

Second Generation

show activity for HENPEcK (H.influenza, Enterobacter aerogenes, N.gonorrhea) Cefotetan & Cefoxitin include Anaerobe Bacteriode fragilis

Third Generation

show activity for HENPEcK plus Serratia marcescens….Ceftazidime have activity against P.aeruginosa….Ceftriaxone & Cefotaxime DOC in Meningitis by H.influenza…..Third generation associated with “Collateral damage”

Fourth Generation:

 activity P.mirabilus, P.aeroginosa,

Resistance:

susceptible to Extended-Spectrum β-lactamase

P.K= i/m or i/v…Cefazolin effective for Orthopedic surgery b/c of S.aureus…Eliminate Through tubular secretion or Glomerular filteration

S.E:

 Thromboplebitis, Toxic epidermal necrolysis, Steven jhonson syndrome




Carbapenems

Differ from Pencillin due to Sulfur in β-lactam ring….Imepinem compounded with Cilastatin to prevent from Renal dehydropeptidase

Monobatams

β-lactam ring not fused with another ring…

 lack activity against Gram-positive & Enterobacter… 

sensitive to Extended-spectrum β-lactamase.

Cause Phelibitis, rash ↑LFT

β-Lactamse inhibitor

Clavulanic acid, Sulbactam, Tazobactam….bind & inactivate β-lactamase….devoid of anti-bacterial activity

Vancomycin

Tricyclic glycopeptides…

 ϴ cell wall phospholipid & peptidoglycan ….

time-dependent action…

prevent Transglycosylation….

Anti-bacterial spectrum:

 activity against MRSA & Enterococci…. VRE, E.faecalis & E.faecium resistant to vancomycin…. treat antibiotic-induce colitis due to C.diificile...

Used in Patient with Prosthetic heart valve undergoing implantation with Prosthetic device .

Resistance: 

replacement of D-Ala by D-lactate…↓ permeability

S.E:

 Red man syndrome (fever, chills, phlebitis)…. Ototoxicity, nephrotoxicity, shock from Histamine release…6-10hr t1/2

Daptomycin

Cyclic peptide…

induce rapid Depolarization…

ϴ RNA,DNA,Protein synthesis…

bactericidal…

conc. Dependent killing

Anti-bacterial spectrum: 

activity against MSSA, MRSA, VRE, E.faecium, E.faecalis

… used in the treatment of Skin infection, Bacteremia, Right-sided infective Endocarditis by S.aureus….

S.E:

 contraindicated in treatment of Pneumonia…. Cause Myalgia, constipation,

↑LFT, ↑Creatine phosphokinase

Telavancin

Semi-synthetic Lipoglycopeptide….

 Disruption of bacterial cell memb. Due to presence of lipophilic side chain...

ϴ cell wall synthesis

Anti-bacterial spectrum: 

Bactericidal against MRSA, S.aureus, S.agalactiae,

S.E

 contraindicated in 30-50ml creatinine clearance in kidney, Pregnancy,… cause Taste disturbance, foamy urine… ↑QT interval, …used to moniter PT/INR, Aptt,,ACT

Bacitracin

Mixture of polypeptide... 

ϴ Cell wall synthesis..

topical use due to nephrotoxicity

Location: Pakistan

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