Patient Risk Factors for Health Care–Associated Infections
Transmission of infection within a health care setting requires three elements: a source of infecting microorganisms, a susceptible host, and a means of transmission for the microorganism to the host.
Source of Microorganisms
During the delivery of health care, patients can be exposed to a variety of exogenous microorganisms (bacteria, viruses, fungi, and protozoa) from other patients, health care personnel, or visitors. Other reservoirs include the patient’s endogenous flora (e.g., residual bacteria residing on the patient’s skin, mucous membranes, gastrointestinal tract, or respiratory tract) which may be difficult to suppress and inanimate environmental surfaces or objects that have become contaminated (e.g., patient room touch surfaces, equipment, medications). The most common sources of infectious agents causing HAI, described in a
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These patients are also more susceptible to rapid microbial colonization as a consequence of the severity of the underlying disease, depending on the function of host defenses and the presence of risk factors (e.g., age, extrinsic devices, extended length of stay). Exposure to these colonizing microorganisms is from such sources as (1) endemic pathogens from an endogenous source, (2) hospital flora in the health care environment, and (3) hands of health care workers. A study related to length of hospitalization examining adverse events in medical care indicated that the likelihood of experiencing an adverse event increased approximately 6 percent for each day of hospital stay. The highest proportion of adverse events (29.3 percent) was not related to surgical procedures but linked instead to the subsequent monitoring and daily care lacking proper antisepsis