I am not really sure exactly what the person who wrote this paragragh
was trying to say, but it seems the false negatives were in the 35 to
50% range for Staph and 82% for vancomycin-resistant Enterococcus.

"The weekly testing for MRSA, the most common superbug, detected more
than half of young patients who were carrying the germ (54 percent, or
one and a half times as many)  than were detected through routine
testing, which missed 35 percent of those with MRSA.  Results for
detecting VRE, a lesser known but still common superbug, were six
times higher with weekly testing than with routine testing, which
missed 82 percent of those with VRE.  Like most bacteria, hospital
superbugs are picked up through direct contact, by touching someone or
a surface with it. "

http://www.hopkinsmedicine.org/Press_releases/2007/04_16_07.html

JOHNS HOPKINS BEGINS AGGRESSIVE SCREENING FOR "SUPERBUGS" IN CHILDREN
- Safety study triggered decision to go beyond standard monitoring and
testing schedules

Infection control and critical care experts at The Johns Hopkins
Hospital have ordered testing for the two most common hospital
superbugs for every child admitted to its pediatric intensive care
unit.

The more stringent admission screening methods for methicillin-
resistant Staphylococcus aureus (MRSA) and vancomycin-resistant
Enterococcus (VRE) go well beyond standard hospital practices, where
tests are only ordered after symptoms or early signs of infection
appear.

The new hospital practice was introduced March 1 after a study
conducted at Hopkins last year showed that more frequent screening
detected many more carriers of the germs before their presence led to
infection or the germs spread to others.

Admission screening is already standard at Hopkins for adults admitted
to intensive care units.

Health experts fear spread of these particular bacteria because they
have developed resistance to the antibiotic drugs most commonly used
to combat them.  Though infections caused by these bacteria are rarely
fatal, carriers of either bug are at greater risk for more dangerous
infections.

Results from the study, to be presented April 16 at the annual meeting
of the Society of Health Care Epidemiology of America (SHEA) in
Baltimore, are believed among the first to make a case for better
screening in efforts to slow spread of the germs in hospitalized
children.

The study compared the effectiveness of weekly screening to current
practices for ordering tests and found the weekly model to be many
times more effective than standard risk monitoring, in which the
highly contagious bacteria are looked for after patients develop skin
rash, fever or pain.

Weekly swab testing and bacterial growth cultures were done on nearly
330 patients in the hospital's pediatric intensive care unit for four
months.  Results were compared to findings of cultures obtained from
patients showing possible signs or symptoms of infection.  All
patients were under age 18.

The weekly testing for MRSA, the most common superbug, detected more
than half of young patients who were carrying the germ (54 percent, or
one and a half times as many)  than were detected through routine
testing, which missed 35 percent of those with MRSA.  Results for
detecting VRE, a lesser known but still common superbug, were six
times higher with weekly testing than with routine testing, which
missed 82 percent of those with VRE.  Like most bacteria, hospital
superbugs are picked up through direct contact, by touching someone or
a surface with it.

"The results were quite clear to us: Aggressive patient safety
programs should consider testing on admission as standard practice,"
says study senior author and hospital epidemiologist Trish Perl, M.D.
Perl and her team, however, will wait for evidence of improved patient
safety before making any national recommendations to government
agencies and other hospitals.

Perl is past president of SHEA and will be presenting at the four-day
conference, expected to attract 1,200 infectious disease specialists,
epidemiologists, nurses and hospital administrators to the city.

"We need to find patients who have these bacteria on them and who, as
such, are not only at risk of personal infection, but also pose a
serious threat of infection to other patients and hospital staff," she
says.

According to Perl, a professor of medicine and pathology at The Johns
Hopkins University School of Medicine, patients found to be infected
or to be a carrier before infection has set in are placed in isolation
for the remainder of their stay.  Wound care is done only in
designated, confined treatment spaces or separate rooms, and hospital
staff must take special precautions between treatments, such as
cleaning equipment and furniture with strong disinfectants and wearing
disposable gloves, masks and gowns.

"Children are more vulnerable to the problem of antibiotic resistance
because their bodies are not fully developed to fight off illness and
because fewer drugs are FDA approved for use in children," says Aaron
Milstone, M.D., a pediatric infectious diseases research fellow at
Hopkins who led the study.

Vancomycin (Vancocin) is currently the only FDA-approved drug for MRSA
in children, and only one drug, linezolid (Zyvox), is approved in
pediatrics for VRE.

Milstone says children admitted to Hopkins are increasingly identified
as harboring MRSA or VRE, with recent reports from the intensive care
unit showing four times as many children with MRSA and twice as many
with VRE than five years ago.  These reports and others led the
Hopkins team to conduct the study.  In 2006, the Joint Commission on
Accreditation of Healthcare Organizations (now known only as the Joint
Commission) estimated that 70 percent of the bacteria that cause
infections for 2 million hospitalized Americans each year are
resistant to at least one of the drugs most commonly used to treat
them.

Funding for the study, conducted solely at Hopkins between June and
September 2006, was provided by the Pediatric Infectious Diseases
Society of America and The Johns Hopkins Hospital.  Besides Perl and
Milstone, other members of the Hopkins team involved in this
investigation and study were Alex Shangraw; Xiaoyan Song, M.D., M.S.;
Ivor Berkowitz, M.D.; and Claire Beers, R.N.

-- JHM --