Introduction to antibacterial drugs Chapter 33 Introduction to antibacterial drugs Shutcm-MBL 1

Microorganism Microorganism is generally used to describe bacteria, fungi, and viruses. [‘kɔksai] 球菌 Bacteria [bə‘silaɪ] 杆菌 ['spaiərəuki:t] 螺旋体 Shutcm-MBL

Infectious diseases caused by bacteria Shutcm-MBL

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 Shutcm-MBL

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 Shutcm-MBL

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 Shutcm-MBL

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 Shutcm-MBL

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. Shutcm-MBL

Drug resistance: relative or complete lack of effect of antimicrobial agent against a previously susceptible microbe. Shutcm-MBL

Postantibiotic effect (PAE) residual antibacterial activity persisting after the serum concentration has fallen below the minimum inhibitory concentration. Shutcm-MBL

Antibacterial mechanisms 1. Inhibit the synthesis of bacterial cell wall; e.g., the β-lactam class agents penicillins, cephalosporins [‘læktæm]内酰胺 Shutcm-MBL

2. Increase the permeability of bacterial cell membrane, leading to leakage of intracellular compounds; e.g., aminoglycosides 3. Inhibit protein synthesis; e.g., aminoglycosides Shutcm-MBL

4. Influence the nucleic acid metabolism; e.g., quinolones Shutcm-MBL

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 Shutcm-MBL

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 Shutcm-MBL

Mechanism of bacterial resistance Shutcm-MBL