Resistance to Beta Lactam Antibiotics

The b-lactam family includes the penicillins and cephalosporins and is the best-known and most widely used group of antibiotics. All contain the b-lactam structure, a four-membered ring containing an amide group, which reacts with the active site of enzymes involved in building the bacterial cell wall. Cross-linking of the peptidoglycan is prevented, so causing disintegration of the cell wall and death of the bacteria. Since peptidoglycan is unique to bacteria, penicillins and cephalosporins have almost no side effects in humans, apart from occasional allergies.

Resistance plasmids carry a gene encoding the enzyme, b-lactamase, which destroys the antibiotic by opening the b-lactam ring (Fig. 16.11). Most b-lactamases prefer either penicillins or cephalosporins, though a few attack both antibiotics equally well. Resistance to ampicillin, a popular type of penicillin, is widely used in molecular ampicillin A widely used antibiotic of the penicillin group beta-lactams or b-lactams Family of antibiotics that inhibit cross-linking of the peptidoglycan of the bacterial cell wall; includes penicillins and cephalosporins beta-lactamase or b-lactamase Enzyme that inactivates b-lactam antibiotics such as ampicillin by cleaving the lactam ring cephalosporins Group of antibiotics of the b-lactam type that inhibit cross-linking of the peptidoglycan of the bacterial cell wall penicillins Group of antibiotics of the b-lactam type that inhibit cross-linking of the peptidoglycan of the bacterial cell wall

Resistance to Chloramphenicol 439

FIGURE 16.11 Inactivation of Penicillin by \-Lactamase

Penicillin is an antibiotic that attacks the cell wall of bacteria, preventing the cells from growing or dividing. The antibiotic has a four-membered \-lactam ring that binds to the active site of the enzymes that assemble the cell wall. The enzyme \-lactamase cleaves the b-lactam ring of penicillin (red bond). The penicillin is inactivated.

Resistance to Chloramphenicol 439

FIGURE 16.11 Inactivation of Penicillin by \-Lactamase

Penicillin is an antibiotic that attacks the cell wall of bacteria, preventing the cells from growing or dividing. The antibiotic has a four-membered \-lactam ring that binds to the active site of the enzymes that assemble the cell wall. The enzyme \-lactamase cleaves the b-lactam ring of penicillin (red bond). The penicillin is inactivated.

Clavulanic acid ry

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