After reading this chapter, the student should understand the following concepts:
The difference among the following types of microorganisms: bacterial, viral, and fungal.
The role of the physician in prescribing medications to alleviate infections.
The different categories of antibiotic drugs and how each works.
The problems associated with antibiotic resistance.
The types of antiviral medications available and how they are used.
The treatment options for topical fungal infections.
The use of the Internet as a source of information about microorganisms.
At certain times, we become susceptible to different types of infections caused by bacteria, viruses, or fungi. Typically, the immune system in the body is strong enough to repel or destroy the invading microorganism. Situations do occur, however, when the body's immune system is not able to combat and control an invasion by one or more of these microorganisms. When microbes overload the natural immune system, the body requires assistance to control the invasion. During these instances, chemotherapeutics (chemical agents that fight organisms such as bacteria, viruses, and fungi) are prescribed to control or eliminate the infection. In this chapter, we will study three categories of chemotherapeutic agents—antibiotics and antiviral and antifungal agents—and discuss their mechanisms of action in fighting invading microorganisms.
Bacteria are classified according to their general structure and makeup. They are small unicellular microorganisms (about the size of mitochondria) contained within a cell wall. Their genetic material is not contained in a true nuclear membrane. Bacteria cells lack the processes of mitosis and meiosis, and their genetic organization is simpler than that of cells in multicellular plants and animals.16 Bacteria are able to maintain cellular metabolism. However, they require nutrients and prefer to steal from their host the necessary amino acids, sugars, and other products they need to sustain life. By understanding the needs of bacteria, we can begin to appreciate how they compete with their human host for these nutrients.
Some bacteria are beneficial to humans. For example, the bacteria in the gastrointestinal (GI) system assist in the digestion of food and help to limit the growth of other microorganisms and excess production of some stomach acids. These helpful bacteria, the normal flora of the GI system, should not be destroyed on a regular basis. However, they are sometimes casualties of antibacterial treatment. It is sometimes necessary to restore these normal GI flora after an antibiotic regimen.
Bacterial infections must be diagnosed and treated by a physician. Treatment of a bacterial invasion is typically accomplished by a regimen of antibiotic therapy. There are several ways to classify antibiotics. For this book we will use the categories of spectrum of activity and method of bacterial control. Antibiotics can be described by their spectrum of activity: either narrow or broad. Narrow-spectrum antibiotics ...