What happened to antibiotics? Once considered the universal answer to infectious disease, we now know the effective life span of these once-miraculous drugs is limited. The problem, simply, is that we “got complacent,” says Barry Kreiswirth of the Public Health Research Institute, who makes a living analyzing strains of tuberculosis that resist as many as nine antibiotics.

It’s not just TB. “The global increase in resistance to antimicrobial drugs, including the emergence of bacterial strains that are resistant to all available antibacterial agents, has created a public health problem of potentially crisis proportions.” That’s the word from the American Medical Association (AMA), which studied the issue in 1995, and seldom fulminates in such alarmist terms.

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The experts are sounding the alarm about antibiotic resistance because of grim new evidence:

Resistance happens quickly, in parallel with the use of antibiotics. An 11-year study of cancer patients at a hospital in Switzerland (see the 4/28/94 New England Journal of Medicine) found that no strains of Escherichia coli (a common intestinal bacteria that can be pathogenic) resisted any of the fluoroquinolone antibiotics between 1983 and 1990. But between 1991 and 1993, 28 percent of the strains tested were resistant to all five of them. During the study period, the percentage of patients getting antibiotics rose from 1.4 percent to 45 percent.

(Updated 1 May, 1998: Under a new National Institutes of Health grant, scientists have begun examining whether harmless bacteria carry resistance genes and transmit them to pathogens. Already, it’s thought that the bacterium Haemophilus influenzae, which causes ear infections, gained resistance to the antibiotic ampicillin during a gene transfer from Escherichia coli, during the 1970s. Why would a harmless bacterium acquire such resistance? Because any organism exposed to antibiotics faces the same selective pressure that causes pathogens to become antibiotic resistant. One leader of the new research group, University of Illinois at Urbana-Champaign microbiologist Abigail Salyers, said resistance can lurk undetected in harmless organisms. She called the presence of resistance in pathogens “the tip of the iceberg compared to what’s out there in the environment.” See “New Hunt for the Roots of Resistance,” Science, 3 April 1998, p. 27. End update.)

It’s widespread. In Atlanta, a 1994 study of infections caused by Streptococcus pneumonia found that 25 percent of 431 patients had a bug that resisted penicillin, and that 25 percent of all cases were resistant to several antibiotics.

It spreads fast: thanks in part to jet planes. Resistant tuberculosis has spread from New York City to Denver, Florida, Nevada and Paris.

Bacteria learn from our mistakes: Once resistance develops, all offspring of that bacterium get it. “Once the resistant strain is made, everybody who is infected with it will have that resistance problem,” says Kreiswirth. And because these organisms then pick up further resistance to other drugs, he says, “All it’s going to do is get worse.” You can skip ahead to our coverage of the mechanisms of resistance.

Hospitals serve as centers for the formation and transmission of drug-resistant organisms. About 2 million Americans are infected in hospitals each year and more than half of these infections resist at least one antibiotic, according to Dennis Maki, a University of Wisconsin-Madison expert in hospital infections. In 1992, 13,300 hospital patients were killed by drug-resistant bacteria in the United States.

Resistance is an especially vexing problem for people with impaired immune systems, such as AIDS, and cancer patients, and recipients of organ transplants. About 90 percent of AIDS patients who get multiple-drug resistant TB die.