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By ABIGAIL ZUGER
March 2, 2004
A new chapter in the continuing story of antibiotic resistance is being written
in doctors' offices across the country, as a group of common bacteria rapidly
becomes resistant to the antibiotics that have been used to treat them for
decades.
The bacteria are called Staphylococcus aureus, or staph for short. Staph
are the most common cause of skin infections like boils and can also cause
lung infections, bloodstream infections and abscesses in the body's internal
organs.
In hospitalized patients, infections caused by antibiotic-resistant staph
have been common for years. Among healthy people, though, antibiotic resistance
in staph has not been a big problem. Since the 1970's, doctors have routinely,
and successfully, treated staph infections in healthy patients with penicillin-like
drugs.
Not anymore. Office doctors who follow this practice now may find their patients
getting sicker instead of better.
Over the last year, Dr. John Gullett, an infectious disease specialist in
Abilene, Tex., has grown accustomed to getting calls for help from local
doctors who have used the usual antibiotics to no effect.
One doctor treated a high school football player "built like Charles
Atlas" with a standard oral antibiotic for a little boil in the groin.
Even though the teenager was the picture of health, the antibiotic did not
work.
The boil, caused by resistant staph, grew into an large abscess tracking
into the leg, and the patient got sicker and sicker. Only when Dr. Gullett
treated him with an intravenous antibiotic generally reserved for desperately
ill hospitalized patients did he turn the corner.
Had the patient's first doctor been aware that the infection was caused by
resistant staph and chosen a different oral antibiotic, the entire episode
might have been milder.
Resistant staph, Dr. Gullet said, are "more invasive and more pervasive" than
the strains most primary care doctors are used to treating.
Dr. Gonzalo Ballon-Landa, an infectious disease specialist at Mercy Hospital
in San Diego, said he was "very concerned about what we are seeing."
Dr. Ballon-Landa has treated clusters of infections from resistant staph
in such disparate groups as prisoners, homeless people, student nurses and
football players.
"Most doctors are just not aware of this," said Dr. Bonnie Bock, an
infectious disease specialist in Newport Beach, Calif., who has treated resistant
staph infections in groups of secretaries, surfers and gay men.
Dr. Bock estimated that about two-thirds of the large staph abscesses she
saw in her office now were caused by the resistant bacteria.
Over all, staph infections are extremely common and often quite minor. Even
staph abscesses, if they are drained properly, may heal without requiring
any antibiotics at all. The new resistant staph can be treated with several
common antibiotics — just not the ones doctors are accustomed to using.
Still, the experts say that some infections caused by the new resistant staph
are unexpectedly aggressive, and delays in starting the right antibiotics
may be life-threatening.
"Staph infections are such a common problem that the emergence of infections
resistant to common antibiotics has important public health implications," said
Dr. Daniel B. Jernigan, an epidemiologist at the federal Centers for Disease
Control and Prevention.
But the infections are so common that they are not reportable to the local
or federal public health authorities. Because of this, detective work to
explain the appearance of the new resistant staph in this country and track
its progress is just beginning.
The resistant staph was first recognized in the United
States among children in Chicago in the mid-1990's.
In 1999, the disease control centers reported that four children in the Midwest
had died of infections with the new staph. Three of them had initially been
treated with the wrong antibiotics.
In the last several years, clusters of infections with the resistant staph
have been reported in jails and prisons in states around the country, including
California, Texas, Pennsylvania and Georgia.
Clusters of skin infections have also been reported among athletic team members
and military recruits.
Pediatricians in Miami and Los Angeles have found that 20 percent to 30 percent
of the serious staph infections they see in nonhospitalized children are
caused by resistant strains. In Houston, rates in children have approached
50 percent.
In the spring of 2002, the health department in Los Angeles learned of a
cluster of resistant staph infections in a group of healthy newborn babies,
followed in rapid succession by an outbreak at the county jail that eventually
involved more than 1,000 inmates, a cluster of infections in a professional
football team, and a cluster of infections among gay men, said Dr. Elizabeth
Bancroft, a medical epidemiologist with the Los Angeles County Department
of Health Services.
Although these infected groups had nothing at all to do with one another,
the bacteria that caused the infections in each group proved to be virtually
identical. Since 2002, the prevalence of the resistant staph in Los Angeles
has increased enormously, Dr. Bancroft said.
Like epidemiologists all over the country, Dr. Bancroft is puzzled by the
origin of the resistant staph and the way it can spread so quickly among
such diverse populations.
One clue may be the bacteria's tendency to "ping-pong" among people,
she said. In a study of children with infections caused by the new resistant
staph, her group found that roughly 30 percent had family members with similar
infections around the same time, suggesting that the staph was highly contagious
and easily passed from one person's skin to another's.
The one thing that newborns, children, prisoners and athletes have in common
is the degree of close body contact they maintain with those around them.
They also share common objects with their peers, toys and equipment, for
example, or soap and towels. They may have difficulty achieving optimal personal
hygiene.
Close living, as in military barracks, also appears to be a risk factor for
infection with the resistant staph, as does having any kind of skin abrasion
or wound, even one as minor as chafing from underclothing or athletic equipment,
Dr. Jernigan said.
This winter, several fatal cases of pneumonia caused by the resistant staph
developed in children with influenza, presumably because the influenza infection
had damaged their lungs, allowing the staph to grow.
Experts are still grappling with the question of where the resistant staph
came from in the first place. It does not appear to have arisen in any of
the most common ways.
Antibiotic-resistant bacteria often develop when people take many antibiotics,
or frequent places like hospitals, where many antibiotics are used. The antibiotics
kill off the sensitive bacteria in people's mouths, intestines and skin,
and the bacteria that are naturally resistant to the antibiotics thrive,
and eventually predominate.
But this process, called "antibiotic pressure" cannot explain the
emergence of the new resistant staph, because among the general public where
these infections appear there is relatively little antibiotic use, and many
people with these infections have never taken antibiotics before.
Did the bacteria simply escape from hospitals, where antibiotic-resistant
staph have been a problem for years? A great deal of evidence suggests that
they did not, Dr. Jernigan said.
The outpatient strains are biologically different from hospital strains,
and the collections of genes that cause antibiotic resistance in the new
strains are quite different from those that cause it in the older strains.
Another ominous difference between the new resistant staph and the old hospital
strains is that the new staph strains appear far more likely to manufacture
a toxin that can destroy the white blood cells that normally fight off infection,
allowing the bacteria to eat through human tissue.
"The concern is that this or other toxins may be responsible for their increased
virulence," said Dr. Franklin D. Lowy, a staph researcher at Columbia University's
College of Physicians and Surgeons in New York, who heads one of five groups
around the country financed by the disease control centers to study the new staph.
"The organism also appears able to replicate more rapidly than others, which
may also cause more serious disease," Dr. Lowy said.
As an example, he described a middle-aged woman with diabetes whom he cared
for recently. The woman developed pneumonia with the new staph, and wound
up spending months on a respirator in the intensive care unit, her lungs
shredded and useless from the infection.
Experts say that heightening doctors' awareness is crucial to tracking and
fighting the new staph.
Staph infections are so common that doctors often just prescribe an antibiotic
without bothering to drain collections of pus and take cultures. Now they
may need to take cultures routinely, and possibly change the usual antibiotics
they prescribe.
Patients, meanwhile, should know that mistaking a staph skin infection for
an insect bite, particularly a spider bite, is an extremely common mistake,
said Dr. Bancroft in Los Angeles, and may lead to delays in treatment.
A skin infection that worsens even with treatment should alert patients to
the possibility of drug resistance. The new staph is resistant to such common
antibiotics as Keflex and Rocephin. It is treated with antibiotics like Bactrim,
Vibramycin and Cleocin.
Hospitals curb antibiotic-resistant organisms by taking a variety of precautions,
including preventing an infected person from skin contact with others, disinfecting
shared objects, and sometimes using antiseptics like chlorhexidine to rid
the skin and other body sites of resistant staph.
It is possible, Dr. Jernigan said, that these measures may now be needed
to control resistant staph infections out of the hospital, too.
http://query.nytimes.com/gst/abstract.html?
res=F40A16FC3C5B0C718CDDAA0894DC404482 |
