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Chapter 2 : Introduction to Major Antibiotic Classes and Modes of Action
Major antibacterial drugs in current human use can be categorized in multiple ways. One is by economic impact and the other is by the bacterial diseases they are prescribed to treat. While the antitubercular drug rifampin and the carbapenem version of the β-lactam imipenem are listed in this chapter, representative brand names are also indicated, as well as infections for which these drugs have been utilized and where clinically significant resistance had been detected. These classes of antibiotics are taken up in detail in the chapter, with discussions of mechanisms of action, modes of resistance development, and prospects for development of new versions to overcome resistance. The gram-positive Mycobacterium tuberculosis still causes millions of deaths annually. The historical scourges of plague and cholera are caused by two gram-negative bacteria, Yersinia pestis and Vibrio cholerae, respectively, while E. coli, Salmonella and Shigella strains are common causes of diarrheal diseases. The gram-negative Pseudomonas aeruginosa is often described as an opportunistic pathogen, causing disease in settings where the patient may have compromised immunity. The mechanisms of action of most antibacterial drugs were worked out after the discovery that the molecules had effects on bacterial growth, either slowing growth dramatically (bacteriostatic) or killing the bacteria (bactericidal). The cell wall biosynthetic processes and protein biosynthesis on the ribosome historically have been the site of action of the largest number of antibiotics, perhaps because of the many enzymatic steps, which offer multiple opportunities for disrupting key attributes of a healthy bacterial cell.