CRITERIA FOR DEFINING NOSOCOMIAL INFECTIONS [INFECTION DUE TO HOSPITAL STAY]
I. Infection is the presence of an organism(s) in body tissue or fluids
accompanied by a clinically adverse effect (either locally or systemically) on
the host. Infection must be distinguished from colonization, which is the
persistence of organisms on skin, in body tissues, or in body fluids but
without a clinically adverse effect, and inflammation, which is a condition
that results from tissue response to injury or stimulation by noninfectious
agents (i.e. chemicals)
Infections that occur during hospitalization but are not present nor incubating
upon hospital admission are defined as nosocomial.
Nosocomial infections may originate from either endogenous or exogenous
sources. Endogenous infections are those caused by microorganisms
already part of the host flora ("normal flora" of the skin, nose, oral cavity,
gastrointestinal tract, etc.) while exogenous infections are those caused by
microorganisms obtained from animate or inanimate sources within the
hospital. The term "nosocomial infection" will thus include potentially
preventable infections as well as some infections that may be regarded as
inevitable.
The Centers for Disease Control of the U.S. Department of Health and
Human Services sets definitions for surveillance of nosocomial infections.
The definitions are based on several important principles.
A. Principles Used in Definitions of Nosocomial Infections
First, information used to determine the presence and classification of an
infection involves various combinations of clinical findings and results of
laboratory and other diagnostic tests. Clinical evidence is derived from
direct observation of the patient or review of information in the patient's
chart or other ward or unit records. Laboratory evidence consists of
results of cultures, antigen- or antibody-detection tests, and microscopic
visualization methods. Supportive data are derived from other diagnostic
studies, such as results of x-ray studies, ultrasound examination,
computed tomography (CT) scan, magnetic resonance imaging,
radiolabel scans, endoscopic procedures, biopsies, and needle
aspiration. For infections whose clinical manifestation in neonates and
infants are different from those in older persons, specific criteria apply.
Second, a physician's or surgeon's diagnosis of infection derived from
direct observation during surgery, endoscopic examination, or other
diagnostic study, or based on clinical judgment, is an acceptable
criterion for an infection, unless there is compelling evidence to the
contrary.
Third, for an infection to be defined as nosocomial, there must be no
