Bacteria that Resist Treatment

By Will Hueston, D.V.M., M.S., Ph.D.

Bacteria once were the major cause of life-threatening diseases in animals and humans. All that changed in the 1940s, with the development of antibiotics such as penicillin. The miracle of modern antibiotics is so widely recognized that Americans have come to expect antibiotics to be sure cures for all that ails them. But the power of these one-time wonder drugs has diminished in recent years as the number and types of bacteria resistant to antibiotics have increased.

Recent studies have highlighted the complexity of antibiotic resistance in both animals and humans. Antibiotic resistance frequently emerges in hospital intensive-care settings. In addition, failure to follow the entire treatment regimen of an antibiotic increases the likelihood of resistance development. Foods can play a role, too, as resistant bacteria can be found contaminating meat and poultry products in grocery stores. While most bacteria prefer either a human or an animal host, some move back and forth. Some resistance apparently can move from people to their pets, as in the recent report that detailed several infections in pets following their owners' resistant-bacterial infection.

The emergence of these "super bugs" and the weakening of antibiotics is a major concern for veterinarians like me, who swear an oath to promote public health as well as protect animal health. Some resistant bacteria even have the potential to cause illness that is untreatable with current antibiotics.

Bacteria become resistant to antibiotics by inheritance, genetic mutation, or sharing of genes among the population. When an antibiotic is given to a sick patient (human or animal), those bacteria lacking resistance die, but those that have some defenses some resistance genes can survive, especially if not enough of the antibiotic is given to kill them. Lacking competition from the susceptible bacteria, these resistant bacteria are likely to multiply.

Many factors contribute to the increase in antibiotic-resistant bacteria, but misuse of antibiotics is a major culprit. The challenge for public health is to sort out which factors contribute most significantly to antibiotic resistance and determine how to focus prevention measures to achieve the greatest reductions in resistance problems.

Unfortunately, there is no single "silver bullet" that will solve this emerging problem. Addressing antibiotic resistance involves a collaborative approach with both human and veterinary medicine. Practices in hospitals, drug sales, and farms all need careful scrutiny. Veterinarians are working at the farm level to develop guidelines and educational programs for judicious use of antibiotics. With a veterinarian's guidance, antibiotics should be targeted to treat animals' infectious diseases, relieve their suffering, and stop the spread of disease. At the same time, certain antibiotics for especially stubborn diseases should be reserved for use in very limited situations only. The veterinary profession is working with production agriculture and public health to implement judicious-use guidelines.

We at the Center for Animal Health and Food Safety are working with public health agencies and those involved in the food system to better understand and fight the growth of antibiotic-resistant bacteria among food animals.

Will Hueston is director of the Center for Animal Health and Food Safety at the University of Minnesota College of Veterinary Medicine. For more information, see the center's Web site: www.cvm.umn.edu/anhlth.html. This is an educational service; advice presented should not take the place of examination by a health-care professional.

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