Bacitracin Vancomycin

Inhibit cell wall synthesis Penicillins, cephalosporins, bacitracin, vancomycin and cycloserine. 

Selective inhibition of bacterial cell wall synthesis (penicillins, cephalosporins, bacitracin, vancomycin). Following attachment to receptors (penicillinbinding proteins), p-lactam antibiotics inhibit transpeptidation enzymes and thereby block the final stage of peptidoglycan sysnthesis. This action is followed by inactivation of an inhibitor of autolytic enzymes in the bacterial cell wall. Bacitracin and vancomycin inhibit early stages of peptidoglycan synthesis. 

Walls, Microbial Cell-Wall Polysaccharides, Bacitracin, Vancomycin, Penicillin... 

Inhibition of cell wall synthesis (p-lactam antibiotics, bacitracin, vancomycin)... 

Inhibitors of cell wall growth, including those that combine with the cell wall substrates, inhibit polymerization and attachment of new agents to the cell wall, combine with carrier molecules and those that inhibit enzymes critical to cell growth. Bacitracin, vancomycin, penicillins, cephalosporins ... 

Lactams Penicillins Cephalosporins Monobactams Carbapenems Vancomycin Bacitracin Cycloserin Fosfomycin Inhibition of synthesis of, or damage to, cell wall... 

The answer is c. (Hardman, pp 1143-1144.) Bacitracin, cycloserine, cephalothin, and vancomycin inhibit cell-wall synthesis and produce bacteria that are susceptible to environmental conditions. Polymyxins disrupt the structural integrity of the cytoplasmic membranes by acting as cationic detergents. On contact with the drug, the permeability of the membrane changes. Polymyxin is often applied in a mixture with bacitracin and/or neomycin for synergistic effects. 

Vancomycin 125 mg orally four times daily x lOdays bacitracin 20,000-25,000 units four times daily x 7-10 days... 

Other inhibitors of cell wall synthesis. Bacitracin and vancomycin interfere with the transport of pepti-doglycans through the cytoplasmic membrane and are active only against gram-positive bacteria. Bacitracin is a polypeptide mixture, markedly nephrotoxic and used only topically. Vancomycin is a glycopeptide and the drug of choice for the (oral) treatment of bowel inflammations occurring as a complication of antibiotic therapy (pseudomembranous enterocolitis caused by Clostridium difficile), it is not absorbed. 

The answer is b. (Hardman, p 1128.) Tetracycline is one of the drugs of choice in the treatment of Rickettsia, Mycoplasma, and Chlamydia infections. The antibiotics that act by inhibiting cell-wall synthesis have no effect on Mycoplasma because the organism does not possess a cell wall penicillin G, vancomycin, and bacitracin will be ineffective. Gentamicin has little or no antimicrobial activity with these organisms. 

The biosynthesis of cell wall peptidoglycan, showing the sites of action of five antibiotics (shaded bars 1 = fosfomycin, 2 = cycloserine, 3 = bacitracin, 4 = vancomycin, 5 = 3-lactam antibiotics). Bactoprenol (BP) is the lipid membrane carrier that transports building blocks across the cytoplasmic membrane M, N-acetylmuramic acid Glc, glucose NAcGIc or G, /V-acetylglucosamine. 

The poly (ribitol phosphate) synthetase and poly (glycerol phosphate) synthetase are inhibited by vancomycin, novobiocin, and Crystal Violet. Other antibiotic substances which interfere with cell-wall synthesis (such as bacitracin, ristocetin, and streptomycin) are almost without effect on the isolated synthetases, and penicillin is inhibitory at high concentrations only. Moreover, penicillin, vancomycin, and bacitracin do not markedly inhibit synthesis of cell-wall glycosaminopeptide in vitro, although the synthetical activity of extracts of cells which have been pretreated with these antibiotics is lowered.Convincing evidence that the primary site of inhibition by antibiotics is the biosynthesis of cell-wall material has been obtained only for the penicillins and cycloserine, and it appears that the action of even those antibiotics may be more complex than was originally supposed. 

The second stage of cell wall synthesis. An ATP-requiring amidation of glutamic acid that occurs between steps 2 and 3 has been omitted. Points of action of the antibiotic inhibitors bacitracin and vancomycin are indicated. 

In addition to penicillin several other antibiotics (phosphonomycin, bacitracin, and vancomycin) block cell wall synthesis at different locations (see figs. 16.16 and 16.17). In addition to their biological and medical importance, these antibiotics have been very useful in elucidating the biosynthetic pathway. This is because they cause accumulation of the intermediate before the blocked step. This species can frequently be isolated and confirmed as a genuine intermediate in the pathway. 

Inhibitors of ceil wall synthesis are suitable antibacterial agents because animal, including human, cells lack a cell wall. These agents exert a bactericidal action on growing or multiplying germs. Members of this class include p-lactam antibiotics such as the penicillins and cephalosporins, in addition to bacitracin and vancomycin. 

Antibacterial drugs that affect cell wall synthesis include two large femilies,the penicillins and cephalosporins, and two individual drugs, bacitracin and vancomycin. 

Paramagnetic ion probes have been successfully used to study the binding characteristics and solution conformations of a number of biochemically important molecules. These include vitamin D, (533) penicillins, (534) and the antibiotics tetracycline, (535-537) vancomycin, (632) and bacitracin. (633) Antibodies and antibody fragments (immunoglobulins, IgG) have been studied by proton relaxation enhancement methods when lanthanide ions, particularly Gd(m), are bound to the proteins. (746-748). 

Figure 2 A selection of nonribosomal peptides. Chemical and structural features that contribute to the vast diversity of this class of metabolites are highlighted Heterocycle (bacitracin), lactone (surfactin, daptomycin), ornithine and lactam (Tyrocidine), sugar, chlorinated aromats, C-C crosslink (Vancomycin), N-formyl groups (Coelichelin and linear gramicidin), fatty acid (daptomycin), dihydroxybenzoate and trimeric organization (bacillibactin), dimeric organization (gramicidin S), and ethanolamine (linear gramicidin).

When the last condensation reaction has occurred, the linear precursor needs to be released from the enzyme. For this important last step, several mechanisms are known simple hydrolysis of the thioester (balhimycin, vancomycin), intramolecular cyclization leading to a lactam (tyrocidine, bacitracin) or a lactone (surfactin), or even reductive thioester cleavage (linear gramicidin). In some cases, the linear precursor is dimerized (gramicidin S) or even trimerized (bacillibactin, enterobactin) before cyclization (Fig. 2). Even though these reactions are critical for the compound s bioactivity, the catalytic domains responsible for the release are not found in all NRPS systems and will therefore be called modifying domains. 

Penicillin, erythromycin, cephalosporin, streptomycin, vancomycin, bacitracin, etc. 

A 65-year-old man undergoing elective sternal debridement and rewiring was given a prophylactic infusion of vancomycin 1 g preoperatively. Anesthesia was induced with thiopental, suxamethonium, and fentanyl, and maintained with fentanyl, vecuronium, and isoflurane. A few minutes after wound irrigation with bacitracin (about 25U/ml), his blood pressure fell precipitously, necessitating intravenous fluids and adrenaline. His face and arms were flushed. Afterwards, he reported having had a rash several years before after the use of an over-the-counter ointment composed of polymyxin B, bacitracin, and neomycin. 

In pseudomembranous colitis (typical endoscopic findings, positive test for C. difficile or its toxin), the preferred treatment is oral metronidazole, 250 mg qds or 500 mg tds (120,167). Metronidazole is as effective as vancomycin 125-250 mg qds, which is significantly more expensive (168). Oral bacitracin 25 000 U qds (169) and oral teico-planin (170) are acceptable alternatives. 

Clinically important, potentially hazardous interactions with aminoglycosides, bacitracin, clindamycin, lithium, procainamide, quinidine, tetracycline, vancomycin... 

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