HYGIENE

Hygiene refers to the health practices that minimize the spread of infectious microorganisms between people or between other living things and people. Inanimate objects and surfaces, such as contaminated cutlery or a cutting board, may be a secondary part of this process.

One of the bedrock fundamentals of hygiene is handwashing. The recognition of the link between handwashing and reduction in microbial illness dates back to the mid-nineteenth century. Then, Florence Nightingale, based on her nursing experiences during the Crimean War, wrote about her perceived relationship between unsanitary conditions and disease. At about the same time, the Viennese physician Ignaz Philipp Semmelweis noted the connection between mortalities in hospital patients and the movement of physicians from patient to patient without an intervening washing of their hands. After Semmelweis introduced hand washing with a solution containing chloride, the incidence of mortality due to puerperal fever (infection after childbirth) diminished from 18% to less than 3%. Now, hand washing with similar antiseptic agents and even with plain soap and water is known to reduce illness and death from hospital acquired infections.

Proper hygienic practices in the hospital setting not only save lives, but save a great deal of money also. According to the Centers for Disease Control, the cost of dealing with the 2.4 million hospital acquired urinary tract infections, blood stream infections, respiratory infections and infections of incisions, which are caused each year by microbes transferred from hospital staff to the patient, and which could be prevented by proper hand washing, is over 4 billion dollars in the United States alone.

Similarly, in the home and other social settings, hand washing can prevent the spread of infectious microorganisms. A common route of infection is from the bathroom to the kitchen. Improper hand washing fails to remove microorganisms, such as Escherichia coli and Salmonella acquired from fecal excretion. Handling of food transfers the organisms to the food.

Hygiene is not so concerned with the bacterial flora that normally resides on the skin. These bacteria include Corynebacterium, Proprionibacterium, and Acinetobacter. These organisms are tenaciously associated with the skin and so are not as easily removed by the mechanical scrubbing action of hand washing. Rather, hygienic efforts such as hand washing attempt to remove organisms, such as Escherichia coli that become transiently associated with the skin. The transient organisms tend be removed more easily and are more apt to be infectious.

In medical environments, hygiene is not only mandatory, but must be done according to established procedures. For example, both before and after seeing a patient, a physician must wash his/her hands with an alcohol-based preparation if hands are not visibly dirty, and with soap and water if dirt is apparent. This practice is also done if any contact with microorganisms has occurred or is even suspected of occurring (for example, handling a surgical instrument that is not wrapped in a sterile package) and after removing surgical gloves. The latter is important since the interior of a surgical glove can be an ideal breeding ground for bacteria. Furthermore, the act of handwashing is to be done for a specified period of time and with vigorous rubbing together of the hands and fingers. This is because the removal of microorganisms is accomplished not only by the presence of the soap but also by the friction of the opposing skin surfaces rubbing together.

Other hygienic practices in a laboratory include wiping the lab bench with a disinfectant compound before and after use and keeping the work area orderly and free of debris. Protective clothing can also be worn to minimize the spread of microorganisms. Such clothing includes hair nets, disposal boots and gloves, and lab coats. These items are worn in the vicinity of the work bench or other areas where microorganisms are expected, but are removed when exiting such locations.

Mechanical aids to hygiene exist. For example, many labs contain a fume hood, in which airflow is directed inward. Such laminar flow hoods do not allow the contaminated air inside the hood to move outward into the laboratory. Another standard feature of a microbiological laboratory is a small flame source. The flame is used to sterilize the lip of test tubes and vials before and after opening the containers, and to heatsterilize the metal inoculating loops used to transfer microorganisms from one place to another.

While necessary for the protection of patients and to prevent contamination in the laboratory, the use of hygienic substances can have adverse effects. In the late 1980s the socalled "hygiene hypothesis" proposed that the increased use of disinfectants, particularly in the home, had decrease the exposure of people to substances that stimulated their immune system, and so had rendered the immune system less capable of dealing with environmental antigens. The result was proposed to be an increase in allergies. Time has strengthened this hypothesis to the point where the overuse of disinfectants has become a legitimate concern.

In addition to the development of allergic reactions, the inadequate or improper use of a hygienic compound can select for organisms that are more capable of causing disease. For example, certain disinfectants containing the compound triclosan have been shown to not only fail to kill the entire target Escherichia coli population, but to actually stimulate the development of resistance in those microbes that survive. In a setting such as a kitchen, the results could be problematic.