Bacterial Diseases

Bacteria get a bad reputation for causing disease when, in reality, very few species of bacteria infect humans. The ones that do, however, are the ones most often written about in magazines and newspapers. These bacteria in­habit the human body because of the constant source of nourishment, moist environment, relatively stable pH and body temperature, and extensive sur­face area.

Contamination with bacteria from the environment can lead to colo­nization, taking up residence on or in the human body. The mixed collec­tion of bacteria that are adapted to the body and reside in it for extended periods of time are called normal flora. Some bacteria inhabit the body only as transients, soon destroyed by human (host) defense mechanisms or re­moved by cleaning. Bacteria that evade host defenses and cause infection are described as virulent. Under certain circumstances, such as an imbalance in normal flora or lowered host resistance, even normal flora can cause in­fection.

Infection may proceed to disease if host defenses do not arrest the in­fection before tissue damage occurs. Bacterial disease can have several out­comes. The immune system may arrest the infection and stop progression of the disease. In other cases, the body may be unable to repair damaged tissues and permanent dysfunction or even death may result. For this rea­son, treatments are designed to stop the infection before permanent dam­age has occurred.

Most bacterial diseases are treated with antibiotics to kill the organisms. In recent years, more and more bacteria have become resistant to the avail able antibiotics. This has forced the scientific community to examine the use of antibacterial agents in soaps and cleansers, the use of antibiotics in animal feeds, and the inappropriate prescription of antibiotics. Patients who terminate the treatment prematurely because they feel better, even though the infection is not yet eliminated, compound the problem of antibiotic re­sistance. All of these situations lead to the killing off of susceptible bacteria while leaving the resistant ones to multiply. The best “medicine” is still pre­vention of infection.

References

Berkow, Robert, et al. The Merck Manual of Diagnosis and Therapy, 17th ed. Rahway, NJ: Merck & Co., 1999.

Levy, Stuart B. “The Challenge of Antibiotic Resistance.” Scientific American (March 1998). www.sciam.com/1998/0398issue/0398levy.html.

Murray, Patrick R., et al. Medical Microbiology, 3rd ed. St. Louis: Mosby-Year Book, 1998.

Staley, James T., et al. Bergey’s Manual of Systematic Bacteriology, 4 vols. Philadelphia, PA: Lippincott, Williams & Wilkins, 1984-1989.