Severe infections by an antibiotic-resistant “superbug,” known as methicillin-resistant Staphylococcus aureus, are at least twice as high as researchers previously believed and now kill more Americans than AIDS, researchers reported today.
The bacterial infections, commonly called MRSA, once were confined to a few hospitals, but a new study by the national Centers for Disease Control and Prevention found that in 2005 they made an estimated 94,000 Americans seriously ill and killed almost 19,000, compared with 17,000 who died of AIDS.
“Certainly, MRSA now has to be viewed as a very important target for prevention and control,” said Dr. David Talan, an infectious diseases specialist in Sylmar, Calif., who was not involved in the study.
The infections have been a growing concern, particularly over the past decade, as they have spread outside hospitals, popping up in prisons, on athletic fields and in locker rooms.
On Tuesday, a high school senior in Bedford, Va., died after being hospitalized for a week with an MRSA infection that spread to his kidney, liver, lungs and heart muscles.
It’s not known how the Virginia student contracted the infection, but officials ordered all 21 schools in the district closed for cleaning today. The bacteria can live on common surfaces, such as a table, for weeks and be transmitted when someone touches it.
The CDC study reported that nearly 14 percent of new antibiotic-resistant staph infections are not linked to hospitals or other medical facilities.
The MRSA estimate is being published with a report that a strain of another bacterium, which causes ear infections in children, has become impervious to every approved antibiotic for youngsters.
The findings, reported in the Journal of the American Medical Association, are the latest evidence of a widespread pattern of increasing drug resistance among a variety of infectious agents, including multi-drug resistant tuberculosis, antibiotic-resistant Clostridium difficile and other once-innocuous organisms.
The emergence of these superbugs has not been accompanied by the development of new drugs to combat them.
The spread of resistant organisms is “astounding,” wrote Dr. Elizabeth Bancroft of the Los Angeles County Department of Public Health in an editorial accompanying the report.
Bancroft said the reported incidence of resistant staph infections is just “the tip of the iceberg” because the CDC researchers only studied blood-borne infections that find their way into internal organisms.
Several studies have found that such infections represent only 6 percent to 9 percent of all MRSA infections, which can also thrive on the skin in a more innocuous form, waiting for an opportunity to enter the body.
“It appears that the total burden of MRSA is much greater than what was estimated in this study,” she said.
Most forms of the staph bacterium are easily killed with common antibiotics, such as amoxicillin. But beginning in 1968, researchers began to see variants that required treatment with stronger antibiotics.
Experts attribute the emergence of the superbugs to indiscriminate use of antibiotics, the failure of patients to complete their antibiotic regimens and the use of antibiotics in animal feed. In each case, incomplete eradication of the bacteria leads to mutations that increase resistance to the drugs.
Today, the most resistant require treatment with powerful and expensive antibiotics like vancomycin, and as many as one in five patients still succumb to the infections.
Confined to the surface of the skin, the bacteria do minimal damage. But in hospitals, nursing homes and dialysis centers, they can hitch a ride inside the body, spreading through the blood stream and causing severe illness.
In the same fashion, they can be spread by tattooing and drug use in prisons and by cuts and abrasions on the athletic field.
While doctors were aware of the growing staph problem, there were no hard data to document it.
The new results were obtained by Dr. R. Monina Klevens of the CDC and her colleagues as part of the agency’s ongoing Active Bacterial Core surveillance program, which monitors infections in nine regions of the U.S., including San Francisco, Baltimore, Atlanta and Denver. All infections were laboratory confirmed.
Infection rates were highest among those over the age of 65, and blacks were twice as likely as whites to suffer an infection. In both groups, Klevens said, the higher rates were most likely due to a higher incidence of chronic diseases, which both weaken patients and sends them more often to the hospital, where they come in contact with the bacterium.
Health-care advocates argue that hospitals need to improve hygiene. Some studies, for example, show that hospital workers wash their hands only about half as often as guidelines recommend.
Other critics say hospitals should screen all newly admitted patients for MRSAs and isolate those who are found to be positive.