Infection Control
Microorganisms are easily transmitted from place to place via vectors such as insects or animals, by humans that can harbor the infectious organism and shed them to the environment, and via movement through the air (in the case of some bacteria, yeast, and viruses). Microorganisms can adapt to antimicrobial treatments (the best example being the acquisition of inheritable antibiotic resistance by bacteria). Thus, the potential for the spread of infection by disease-causing microbes is substantial unless steps are taken to limit the spread. Such strategies are collectively termed infection control.
For many microorganisms, particularly bacteria, contact transmission is a common means of spread of infection. This can involve the fecal-oral route, where hands soiled by exposure to feces are placed in the mouth. Day care workers and the infants under their charge are a significant focus of such Escherichia coli infections. As well, touching a contaminated inanimate surface is a means of transmitting an infectious microorganism.
The contact route of transmission is the most common route in the hospital setting. Various steps can be taken to control the spread of infection through contact with contaminated surfaces. Proper handwashing, in fact, is the single most effective means of preventing the spread of infection. Thorough handwashing prevents spread of bacteria to others and also prevents contamination of work or food preparation surfaces.
The operating theatre is an example of a place where the importance of infection control measures is apparent. In the nineteenth century, before the importance of hygienic procedures was recognized, operations were used as a last resort because of the extremely high mortality rate after surgery. Pioneering efforts by scientists such as Joseph Lister made operating rooms much cleaner, which resulted in a drop in the death rate attributable to surgically acquired infections. In the present day, operating rooms are places where personal hygiene is meticulous, instruments and clothing is sterile, and where post-operative clean up is scrupulous.
In hospitals and particularly in research settings, the control of infections involves the use of filters that can be placed in the ventilation systems. Such filters prevent the movement of particles even as small as viruses from a containment area to other parts of a building. Work surfaces are kept free of clutter and are exposed to disinfectant both before and after work with microbes, to kill any transient organisms that may be on the inanimate surface. Laboratories often contain containment structures called fume hoods, in which organisms can be worked with isolated from the airflow of the remainder of the lab. Even the nature of the work surface is designed to thwart infection. Surfaces are constructed so as to be very smooth and to be watertight. The presence of crevasses and cracks at the junction between surfaces are ideal spots for the collection and breeding of infectious microorganisms.
Some infectious microorganisms can be transferred by animal or insect vectors. One example is the viral agent of Yellow Fever, which is transmitted to humans via the mosquito. Control of such an infection can be challenging. Typically a concerted campaign to kill the breeding population of the vector is required, along with measures to protect people from those vectors that might escape the eradication campaign. To use the Yellow Fever example, spraying in mosquito breeding sites could be supplemented with the use of mosquito netting over the beds of people in particularly susceptible regions.
Another strategy of infection control is the use of antimicrobial or antiviral agents in an effort to either defeat an infection or, in the case of vaccines, to protect against the spread of an infection. Antibiotics are an antimicrobial agent. They have been in common use for less than 75 years, and already history is showing that antibiotics achieve success but that this success should not be assumed to be everlasting. Bacteria are proving to be adept at acquiring resistance to many antibiotics. Indeed, already strains of enterococci and Staphylococcus aureus are known to be resistant to virtually all antibiotics currently in use.
Immunization against infection is a widely practiced and successful infection control strategy. Depending upon the target microbe, the vaccination program may be undertaken to prevent the seasonal occurrence of a malady such as influenza, or to eradicate the illness on a worldwide scale. An example of the latter is the World Health Organization's effort to eradicate polio.
One breeding ground for the development of resistant microbial populations is the hospital. Antibiotics and disinfectants are an important part of the infection control strategy in place in most hospitals. Bacteria are constantly exposed to antibacterial agents. The pressure to adapt is constant.
The degree of infection control is tailored to the institution. For example, in a day care facility, the observance of proper hygiene and proper food preparation may be adequate to protect staff and children. However, in a hospital or nursing home, where people are frequently immunocompromised, additional measures need to be taken to ensure that microbes do not spread. Such measures can include regular disinfection of surfaces, one-time use of specific medical equipment such as disposable needles, and well-functioning ventilation systems.
The focus of infection control strategies has shifted with the emerging knowledge in the 1970s and 1980s of the existence and medical relevance of the adherent bacterial populations known as biofilms. These adherent growths can remain viable on surfaces after being treated with concentrations of chemicals that swiftly kill their free-floating counterparts. Infection control in areas such as physician and dentist offices, now focus on ensuring that equipment is free from biofilms, because the bacteria could be easily transferred from the equipment to a patient.
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