Researchers Suggest Adding New Classification for Bloodstream Infections
DURHAM, N.C. -- Hospitals and disease surveillance agencies
should consider adding a third category -- "health
care-associated infections" -- to the system currently used to
classify bloodstream infections in patients, according to Duke
University Medical Center researchers.
The proposed new category would describe those infections
originating in non-hospital medical settings, such as nursing
homes, outpatient dialysis and chemotherapy clinics and home
health services. The researchers say adding this new category
would help guide diagnostic and treatment decisions. The two
current infection categories are "hospital-acquired" and
The Duke researchers report their findings and
recommendations in today's (Nov. 19, 2002) issue of the Annals
of Internal Medicine.
"Currently, we only classify infections as hospital-acquired
and community-acquired," said Deborah Friedman, M.B.B.S.,
currently an infectious diseases physician at Victorian
Infection Control Nosocomial Infection Surveillance System in
Melbourne, Australia, and lead author of the study. The study
was completed while Friedman was a fellow in infectious
diseases at Duke University Medical Center.
"However, with the wide variety of outpatient medical
services currently available, there is the potential for
patients receiving outpatient care to develop infections that
were historically associated exclusively with a hospital stay,"
said Friedman. "The irony is that we still classify those
infections as community-acquired, even though they may well
have originated in a medical setting."
The Duke team studied 504 patients with bloodstream
infections detected by blood cultures at three hospitals
(including one tertiary care center and two community
hospitals). Each infection was classified as either:
- hospital-acquired (nosocomial) -- an infection detected
after the patient had been hospitalized for 48 hours or
- community-acquired -- an infection diagnosed upon
hospital admission or within 48 hours of admission in
patients who had not had significant recent contact with the
health care system; or
- health care-associated -- diagnosed upon admission to the
hospital, or within 48 hours of hospital admission, in
patients who had recent contact with the health care system
in the form of home health care, outpatient intravenous
therapy (for example, chemotherapy or dialysis), nursing
homes or recent hospitalization.
This study was funded by an educational grant from Merck
The Duke researchers found that of the 504 patients studied,
175 had hospital-acquired infections, 143 had
community-acquired infections and 186 suffered health
care-associated infections. Moreover, Staphylococcus aureus (S.
aureus) represented the most common cause of hospital-acquired
and health care-associated infections, while community-acquired
infections were more commonly associated with Escherichia coli
(E. coli) and Streptococcus pneumoniae.
"The primary advantage of having the health care-associated
category is that it would assist physicians in providing swift
and accurate diagnosis and treatment of infections," said
Daniel Sexton, M.D., professor of medicine at Duke University
Medical Center and senior author of the study.
Standard antibiotics are often effective in the treatment of
community-acquired infections. However, hospital-acquired and
health care-associated infections are similar in that they
often require more sophisticated treatments because the
infections are often resistant to standard antibiotics, said
Hospital-acquired infections are considered the most
difficult infections to treat, said the researchers. Because
they occur only after a patient has been hospitalized for
another medical condition, treatment has to be considered in
light of patients' existing medical problems. Hospital-acquired
infections are also more likely to be resistant to antibiotics
than are community-acquired infections, said the
"For example, methicillin-resistant Staphylococcus aureus
(MRSA) is an infection that has historically been associated
almost exclusively with hospital settings," said Sexton.
MRSA are strains of S. aureus that do not respond to
treatment with the standard and preferred choice of
The Duke researchers found that MRSA occurred with similar
frequency in patients with hospital-acquired infections (61
percent) and health care-associated infections (52 percent),
but was uncommon in patients with community-acquired infections
"This finding underscores our hypothesis that more serious
infections are being spread in non-hospital settings than
physicians are traditionally trained to expect," said Keith
Kaye, M.D., assistant professor of medicine at Duke University
Medical Center and a study co-author.
Differentiating between community-acquired and health
care-associated infections would aid physicians'
decision-making process when evaluating treatment options for
patients who appear not to have been infected during a hospital
stay, said the researchers.
"The current practice is to use standard antibiotics for
community-acquired infections, and more sophisticated
treatments for hospital-acquired infections that are more
likely to be antibiotic resistant," said Kaye. "However, this
study shows that a high percentage of patients with health
care-associated infections also have resistant infections, and
that we would be wise to approach treatment of these infections
in a similar manner as we now treat hospital-acquired
"Essentially, modern medical science has resulted in shorter
hospital stays for many conditions," said Friedman. "Any number
of medical conditions can now be managed on an outpatient
basis, which is an advantage for patient quality-of-life.
However, it means that there are more people with weakened
immune systems living in general society and receiving
outpatient or nursing home care. Our current infection control
system does not account for the fact that these patients are
being exposed to and are susceptible to infectious agents that
are generally associated with a hospital setting."
Adding the health care-associated category of infection
would also have implications for infection control surveillance
practices, said Friedman.
"Currently, most infection control programs only monitor
rates of infections within hospitals and hospital-affiliated
clinics, said Kaye. "Including health care-associated
infections in surveillance would result in more extensive
tracking of infection rates and sources in outpatient clinics
and nursing homes, which in turn would provide more
opportunities for intervention and prevention of the spread of
Joining Friedman, Sexton and Kaye on this study were Jason
Stout, M.D., Sarah McGarry, M.D., Sharon Trivette, Jane Briggs,
Wanda Lamm, Connie Clark, Jennifer MacFarquhar, Aaron Walton,
M.D. and L. Barth Reller, M.D., all of Duke University Medical