Control of Microbial Growth

■ he British Medical Journal stated that the British physician

■ Joseph Lister (1827-1912) "saved more lives by the intro-JL. duction of his system than all the wars of the 19th century together had sacrificed." He revolutionized surgery by developing effective methods that prevent surgical wounds from becoming infected. Impressed with Pasteur's work on fermentation (said to be caused by "minute organisms suspended in the air"), Lister wondered if "minute organisms" might be responsible also for the pus that forms in surgical wounds. He then experimented with a phenolic compound, carbolic acid, introducing it at full strength into wounds by means of a saturated rag. Lister was particularly proud of the fact that, after carbolic acid wound dressings became standard in his practice, his patients no longer developed gangrene. Lister's work provided impressive evidence for the germ theory of disease, even though microorganisms specific for various diseases were not identified for another decade.

Later, Lister improved his methods by introducing surgical procedures that excluded bacteria from wounds by maintaining a clean environment in the operating room and by sterilizing instruments. These procedures were preferable to killing the bacteria after they had entered wounds because they avoided the toxic effects of the disinfectant on the wound.

Lister was knighted in 1883 and subsequently became a baron and a member of the House of Lords.

—A Glimpse of History

UNTIL THE LATE NINETEENTH CENTURY, PATIENTS undergoing even minor surgery were at great risk of developing fatal infections due to unsanitary medical practices and hospital conditions. Physicians did not know that their hands could pass diseases from one patient to the next. Nor did they understand that airborne microscopic organisms could infect open wounds. Fortunately, today's modern hospitals use rigorous procedures to avoid microbial contamination, allowing surgical operations to be performed with relative safety.

The growth of microorganisms affects more than our health. Producers of a wide variety of goods recognize that, unless microbial growth is controlled, the quality of their products can be compromised. This ranges from undesirable changes in the safety, appearance, taste, or odor of food products to the decay of untreated lumber.

This chapter will cover the methods that have been developed to destroy, remove, and inhibit the growth of microorgan-

Medical settings warrant a high level of microbial control

isms on inanimate objects and some body surfaces. Most of these approaches are non-selective in that they can adversely impact all forms of life. Antibiotics and other antimicrobial medications will be discussed in chapter 21. These compounds are particularly valuable in combating infectious diseases because their toxicity is specifically targeted to microbes.

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