In a disturbing sign of the growing danger of drug-resistant microbes, a new federal survey of people with pneumococcal infections found that 25% had strains resistant to penicillin, which was once nearly infallible in killing the bugs.
That figure is a thousand times greater than estimates made only a decade ago, indicating that antibiotic-resistant pneumococcus germs have spread quickly and are now more common than researchers believed. Moreover, among one group of children under 6 years of age with pneumococcal infections, more than 40% had strains resistant to penicillin.
The pneumococcal bacteria cause pneumonia, meningitis and other diseases. Doctors worry about antibiotic resistance because it renders drugs weakened--requiring much higher doses--or useless.
The study of 431 people in Atlanta--by researchers at Emory University and the Centers for Disease Control and Prevention--is the most thorough analysis yet of the prevalence of drug-resistant pneumococcus in a U.S. city. "We were quite shocked," said Dr. Martin S. Cetron, a CDC epidemiologist involved in the study. He added, "This gives us the first handle on the extent of the problem, at least in Atlanta."
In Los Angeles, no comparable citywide figures are available. But at the UCLA Medical Center last year, 17% of patients with documented pneumococcus infections were afflicted by a penicillin-resistant bug, according to Dr. Peter Katona, head of infection control there. "That's pretty high," he said. "It used to be very low."
However, at Los Angeles County-USC Medical Center, the director of the microbiology laboratories, Maria Appleman, said just one case of penicillin-resistant pneumococcal infection was documented there last year.
She suggested that a possible reason for the low level of drug resistance was the large number of indigent people treated there. Researchers have generally found that drug-resistant bacteria are most common among well-to-do patients with ready access to antibiotics. Presumably, researchers say, heavy antibiotic use wipes out many strains of a bug, leaving the resistant survivors to dominate.
The Atlanta study supports that idea. Drug-resistant pneumococcus infections were twice as common among suburban blacks as among inner-city blacks.
The group with the highest proportion of drug-resistant infections--41%--was white children 6 and under. Other studies have shown that pediatricians make especially heavy use of antibiotics in this group and that day-care centers are prime incubators of antibiotic-resistant infections.
Americans spend an estimated $4 billion annually treating diseases caused by pneumococcus bacteria. They include 500,000 cases of pneumonia; 55,000 cases of bacteremia, a blood infection; 6,000 cases of meningitis, and as many as 6 million inner-ear infections.
In addition to the "disturbingly high" level of penicillin resistance, the Atlanta researchers found that 25% of the pneumococcus samples were resistant to at least three other commonly used antibiotics. However, none of the samples were resistant to the last line of defense, the drug vancomycin.
The study had been scheduled to cover all of 1994, but striking early results prompted the researchers to curtail it by two months to rush the findings into print. It appears in today's New England Journal of Medicine.
Over the last decade, medical scientists have grown increasingly concerned about the emergence of antibiotic resistance as seemingly vanquished microbes have bounced back, newly endowed with an ability to fend off the antibiotic drugs that are the glory of 20th-Century medicine. In addition to the pneumonia bugs, those that cause tuberculosis, gonorrhea, staph infections and certain intestinal diseases have also humbled medical scientists by proving that the victory over infectious diseases was not final.
"We've been lucky it hasn't hit us sooner," Dr. Robert Austrian, a distinguished infectious disease specialist at the University of Pennsylvania School of Medicine, said of the emergence of drug-resistant pneumococcus.
Drug resistance poses an especially serious obstacle to treating pneumococcal meningitis, an often fatal infection of the lining of the brain and spinal cord. Blood flow to those tissues is minimal, so it is difficult to mount a heavy antibiotic assault on infections ensconced there.
Pneumonia is somewhat easier to overwhelm, largely because massive amounts of antibiotic readily reach the lungs. In the same issue of the New England Journal, researchers in Barcelona, Spain, where high levels of penicillin-resistant pneumonia germs had previously been documented, showed that the disease was no more fatal when caused by drug-resistant bugs than normal bugs--provided that patients were treated with massive drug doses.
Still, the Barcelona researchers have also observed an "alarming" rise in pneumonia bugs resistant to the drug cephalosporin, a second line of defense after penicillin.
Following up on the Atlanta work, researchers are planning to determine the prevalence of drug-resistant pneumococcus infections in eight other U.S. cities. "What we would like is a sort of weather map" of the bugs, Cetron said.
To counteract the rise in drug resistance, researchers suggest that new antibiotics be developed, that more Americans consider taking the currently available pneumonia vaccine and that doctors cut back on the indiscriminate use of antibiotics.
"Don't go and ask your doctor for an antibiotic if you just have a cold," said UCLA's Katona. "If you do, you are contributing to the emergence of drug-resistant bacteria. "