The Growing Problem of Antibiotic Resistance 张驰

王昳楠

Have we conquered bacteria yet?

Why the pharmaceutical industry has cut resources devoted to the development of new antibiotics Lack of financial incentives

Short lifetime in the marketplace

The most effective antibiotics being held back from widespread use

Enzymes involved in the synthesis of the bacterial cell wall

Penicillin Vancomycin

Components of the system by which bacteria duplicate, transcribe, andtranslate their genetic informationLinezolid Daptomycin

3. Enzymes that catalyze metabolic reactions specifically in bacteria.

Sulfa drugs, are effective antibiotics because they closely resemble the compound p-aminobenzoic acid (PABA)

Take sulfa drugs for example

p-aminobenzoic acid Sulfa

Function of PABA

PABA is an intermediate in the bacterial synthesis of folate(folic acid).

However, humans lack the enzymes to convert PABA to folate,and therefore require a dietary supply of folate anyway,so PABA is considered nonessential and is not recognized as a vitamin for humans.

Thus, bacterial growth is limited through folate deficiency without effect on human cells.

Function of Sulfa drugs

Sulfa drugs are structurally similar to PABA, and their antibacterial activity is due to their ability to interfere with the conversion of PABA to folate by the enzyme dihydropteroate synthetase.

Why bacteria become resistant to antibiotics?

Take Penicillin for example

Penicillin is a β-lactam; that is, it contains a four- membered β-lactam ring (shown in color).

Background By the 1940s, researchers had discovered that certain

bacteria possess an enzyme calledβ-lactamase(or penicillinase).

During World War II, none of the major disease-causing bacteria possessed a gene for β-lactamase.

Today, the production of β–lactamase by wide variety of infectious cells is the primary cause of penicillin resistance.

How didthese species acquire the gene?

—— not only among the cells of a given species, but also between species

Accessions

Conjugation

Transduction

Transformation

Conjugation

DNA is passed from one bacterial cell to another

Transduction

a bacterial gene is carried from cell to cell by a virus

Transformation

a bacterial cell is able to pick up naked DNA from its surrounding medium

Other reasons of bacteria’s resistant

possess modifications in their cell walls that block entry of the antibiotic

selectively export the antibiotic once it has entered the cell

possess modified transpeptidases that fail to bind the antibiotic

Not all penicillin-resistant bacteria have acquired aβ–lactamase gene.

About AIDS

high rate of virus production

reverse transcriptase lead to high rate of mutation

This problem is being combatted by

Taking several different drugs targeted at different viral enzymes

designing drugs that interact with the most highly conserved portions of each targeted enzyme

Antibiotic abuse

Antibiotic resistant bacteria is a growing threat and becoming increasingly common.

Antibiotic abuse also places the patient at unnecessary risk of adverse effects of antibiotics.

Thank you ~