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Chapter 5 : Antibiotics That Inhibit Bacterial Cell Wall Synthesis

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Antibiotics That Inhibit Bacterial Cell Wall Synthesis, Page 1 of 2

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Abstract:

This chapter explains how penicillin and structurally related antibiotics kill bacteria. The authors introduce an antibiotic called vancomycin that has become an important frontline drug for treating bacterial infections that are resistant to other antibiotics. Structures of antibiotics are illustrated in the chapter. Penicillins and a related type of antibiotic called cephalosporins have long been mainstays of antibiotic therapy. Recently, two more types of β-lactam antibiotics have been added to the β-lactam family: carbapenems and monobactams. The success of the β-lactam antibiotics, both in terms of efficacy and safety, was so impressive that little attention was paid for a long time to another antibiotic that also inhibited bacterial cell wall synthesis: vancomycin. When vancomycin was first discovered, physicians much preferred antibiotics that were effective against all bacteria, gram positive as well as gram negative. A likely explanation is that the use of antibiotics that were most effective against gram-negative bacteria allowed the gram-positive bacteria to reclaim their starring role in the infectious diseases. Virtually all of the resistance strategies described in the chapter involve a single resistance protein, an enzyme that inactivates the antibiotic or an altered antibiotic target that is no longer affected by the antibiotic. There may be some gram-positive bacteria that are naturally resistant to vancomycin because they have peptides in their peptidoglycan that do not have a terminal D-alanine-D-alanine peptide.

Citation: Salyers A, Whitt D. 2005. Antibiotics That Inhibit Bacterial Cell Wall Synthesis, p 50-65. In Revenge of the Microbes. ASM Press, Washington, DC. doi: 10.1128/9781555817602.ch5

Key Concept Ranking

Bacterial Pathogenesis
0.67774683
beta-Lactam Antibiotics
0.4497121
Bacterial Cell Wall
0.43286166
Bacterial Cytoplasmic Membrane Proteins
0.416971
0.67774683
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Figures

Image of Figure 5.1
Figure 5.1

Comparison of the structures of gram-positive and gram-negative bacteria. The cytoplasm of both types of cells is surrounded by a cytoplasmic membrane. Outside the cytoplasmic membrane is the complex mesh-like polymer, peptidoglycan. The peptidoglycan in the gram-positive cell wall consists of many layers. Other substances such as lipoteichoic acid are woven through the peptidoglycan. Gram-negative cells have a thin layer of peptidoglycan, which is covered by an outer membrane. The outer membrane consists of one layer of phospholipids and one layer of lipopolysaccharide.

Citation: Salyers A, Whitt D. 2005. Antibiotics That Inhibit Bacterial Cell Wall Synthesis, p 50-65. In Revenge of the Microbes. ASM Press, Washington, DC. doi: 10.1128/9781555817602.ch5
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Image of Figure 5.2
Figure 5.2

The structure of peptidoglycan. Peptidoglycan consists of chains of glycans (sugars) that are linked together with chains of amino acids (peptides).

Citation: Salyers A, Whitt D. 2005. Antibiotics That Inhibit Bacterial Cell Wall Synthesis, p 50-65. In Revenge of the Microbes. ASM Press, Washington, DC. doi: 10.1128/9781555817602.ch5
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Image of Figure 5.3
Figure 5.3

The structure of members of the penicillin family of antibiotics (β-lactams). This family of antibiotics is characterized by a four-membered ring (the β-lactam ring).

Citation: Salyers A, Whitt D. 2005. Antibiotics That Inhibit Bacterial Cell Wall Synthesis, p 50-65. In Revenge of the Microbes. ASM Press, Washington, DC. doi: 10.1128/9781555817602.ch5
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Image of Figure 5.4
Figure 5.4

Cross-linking occurring during the synthesis of peptidoglycan. Sugar-peptide units are formed in the cytoplasm of the cell. These units are then exported across the cytoplasmic membrane to the exterior where they are assembled into peptidoglycan.

Citation: Salyers A, Whitt D. 2005. Antibiotics That Inhibit Bacterial Cell Wall Synthesis, p 50-65. In Revenge of the Microbes. ASM Press, Washington, DC. doi: 10.1128/9781555817602.ch5
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Image of Figure 5.5
Figure 5.5

The structure of clavulanic acid.

Citation: Salyers A, Whitt D. 2005. Antibiotics That Inhibit Bacterial Cell Wall Synthesis, p 50-65. In Revenge of the Microbes. ASM Press, Washington, DC. doi: 10.1128/9781555817602.ch5
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Image of Figure 5.6
Figure 5.6

The mechanism of vancomycin resistance. Two enzymes in the resistance pathway replace the -alanine--alanine with -alanine--lactate, which does not bind vancomycin. One enzyme links -lactate to -alanine. A second one converts pyruvate, an intermediate in glycolysis, to -lactate. A third enzyme hydrolyzes any normal -alanine--alanine peptides that might form and be bound by vancomycin. The cross-linking enzymes of the cell seem to be able to handle -alanine--lactate and thus do not need to be modified. The encircled V represents vancomycin, which is no longer able to bind. (Reprinted from A. A. Salyers and D. D. Whitt, , ASM Press, Washington, D.C., 2002.)

Citation: Salyers A, Whitt D. 2005. Antibiotics That Inhibit Bacterial Cell Wall Synthesis, p 50-65. In Revenge of the Microbes. ASM Press, Washington, DC. doi: 10.1128/9781555817602.ch5
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