1. Introduction to antibacterial drugs
Chapter 33
Introduction to antibacterial drugs
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2. Microorganism
Microorganism is generally used to describe bacteria, fungi, and viruses.
[‘kɔksai] 球菌
Bacteria
[bə‘silaɪ] 杆菌
['spaiərəuki:t]
螺旋体
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3. Infectious diseases caused by bacteria
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4. Antimicrobial drugs
Definition: are natural or synthetic chemical substances that suppress the growth of, or destroy, microorganisms including bacteria, fungi, and viruses.
Include：
antibacterial drugs
antifungal drugs
antiviral drugs
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5. Antibacterial drugs: drugs which can inhibit or kill bacteria and be used to treat related infectious diseases, include antibiotics and synthetic antimicrobial agents. Antibiotics: are antibacterial substances produced by various species of microorganisms (bacteria, fungi, and actinomycetes) that suppress the growth of other microorganisms.
[,æktinəumai'si:t]
放线菌
Alexander Fleming
弗莱明
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6. Anti-bacterial spectrum: the range of drug’s antimicrobial activity.
• “narrow spectrum” antibiotics: penicillins
• “broad spectrum” antibiotics:
cephalosporins
quinolones
doxycycline
chloromycetin
[,peni‘silin] 青霉素
[,sefələ‘spɔ:rin] 头孢菌素
[‘kwinələun]喹诺酮
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7. Antibacterial activity
Bactericidal drugs: not only inhibit the growth and propagation of bacteria, but also kill them, include penicillins, cephalosporins, aminoglycosides;
Bacteriostatic drugs: only inhibit the growth and propagation of bacteria, like sulfonamides.
[bæk,tiəri‘saidəl] 杀菌药的
[,æminə'ɡlikəsaid]
氨基糖甙类
[bæk,tiəriə‘stætik] 抑制细菌的
[sʌl'fɔnəmaid]
磺胺类
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8. MIC (minimum inhibitory concentration): the lowest concentration to prevent visible growth of a bacterium in standard condition for 24 h; MBC (minimum bactercidal concentration): the lowest concentration for killing 99.9% of tested bacteria.
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9. Drug resistance: relative or complete lack of effect of antimicrobial agent against a previously susceptible microbe.
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10. Postantibiotic effect (PAE) residual antibacterial activity persisting after the serum concentration has fallen below the minimum inhibitory concentration.
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11. Antibacterial mechanisms
1. Inhibit the synthesis of bacterial cell wall; e.g., the β-lactam class agents penicillins, cephalosporins
[‘læktæm]内酰胺
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12. 2. Increase the permeability of bacterial cell membrane, leading to leakage of intracellular compounds; e.g., aminoglycosides 3. Inhibit protein synthesis; e.g., aminoglycosides
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13. 4. Influence the nucleic acid metabolism; e.g., quinolones
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14. 5. Inhibit the folic acid (folate) synthesis in bacteria e. g
5. Inhibit the folic acid (folate) synthesis in bacteria e.g. sulfonamides 叶酸
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15. Bacterial resistance to antibacterial drugs
More than 70% of the bacteria associated with hospital-acquired infections in the United States are resistant to one or more of the drugs previously used to treat them.
Mechanisms:
1) Produce enzymes that inactivate the antibacterial drugs;
2) Alter drug binding site or target site;
3) Decrease drug accumulation in bacteria;
4) Develop pathways that bypass drug’s action.
The drug does not reach its target, the drug is not active, or the target is altered
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16. Mechanism of bacterial resistance
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