"SUPERBUG" BACTERIA

The epidemic raged through the hospital nursery, endangering or infecting newborn babies. It was 1960, when penicillin was still effective against most pathogenic bacteria, but a new strain of Staphylococcus aureus had emerged—a strain that was resistant to penicillin.

I was a research assistant at a large teaching hospital in the Chicago area, and found myself assigned to finding the source of the infection. Was there a Typhoid Mary on the staff? Some cleaning woman or nurse's aide, perhaps? There was only one way to find out. For several weeks I moved from one room on the nursery floor to another, taking nasal swabs from every person who entered the room, then culturing the bacteria from them in the laboratory. It made me less than popular with the nursing staff, but the hospital administrators had given strict orders about the need for cooperating with my study. My results did indeed show the source of the infection—the pediatricians who moved from one baby to another without thoroughly washing their hands.

At that time hospital-acquired infections were much rarer than they are today. The “magic bullet” penicillin was given routinely to control infections as soon as they appeared. But the appearance of penicillin-resistant bacteria was a red flag for biologists, if not for much of the medical profession. Pharmaceutical companies responded by modifying the structure of penicillin to create methicillin, and for a time methicillin controlled all the bacteria that were resistant to penicillin. Eventually, some strains of bacteria emerged that were resistant to methicillin; now we call them methicillin-resistant Staphylococcus aureus, or MRSA. Some bacteria failed to be controlled by other antibiotics, also. Today many infections still respond to various antibiotics, but occasionally they do not.

How did this come about? As Charles Darwin realized in the nineteenth century, evolution occurs when something in the environment kills part of a species before it can reproduce. (This is what is meant by natural selection.) In a population of Staphylococcus (staph), some of the bacteria contain mutations that make them vulnerable to a given antibiotic, but other bacteria may be resistant to it. If an infection is treated with the antibiotic, only the resistant bacteria survive and reproduce. Bacteria multiply rapidly; soon, many resistant bacteria are in the environment.

Though antibiotics can be lifesaving when necessary, their misuse has led to selection for resistant bacterial strains. Most physicians are aware of the problem. However, even now many people continue to insist on being given antibiotics at the first sign of an infection, or even as a preventive measure.

In 2011 an infection spread through a National Institutes of Health (NIH) hospital near Washington, D.C. Caused by a drug-resistant strain of Klebsiella pneumoniae, it infected 18 patients and killed six of them. Carbapenem-resistant Enterobacteriaceae (CRE) is another danger: it is a particularly nasty class of bacteria that causes serious intestinal illness and is fatal in about 50% of cases. It is resistant to the powerful class of antibiotics called carbapenems. So far CRE has been found mainly in hospitals, but it has spread to most states now, and it seems inevitable that it will spread to the general community.

How can we aging people avoid getting these infections, which are especially dangerous to the elderly? One strategy is a no-brainer—stay out of hospitals! Many procedures can be done in outpatient settings today, which costs less and is less likely to lead to infections. If we do have to be in a hospital, we should forget politeness and insist that anyone who touches or even breathes on us wash their hands or use alcohol-based sanitizers. Beyond that, there is little we can do now except to stay as healthy as possible. Our bodies contain many “good” bacteria that help protect us against dangerous pathogens; if we are generally in good health and have not destroyed those helpful bacteria, we have a good chance of staying free of “superbug” infections.