The National Institute for Animal Agriculture opened its conference titled “Bridging the Gap between Animal Health and Human Health” on Tuesday afternoon in Kansas City. Presentations on antimicrobial resistance in human medicine from physicians and scientists from the U.S. Centers for Disease Control and Prevention (CDC), state health departments and academia helped set the stage for the rest of the conference by providing background on the history and current state of antimicrobial resistance.

Steven Solomon, M.D., director of the office of antibiotic resistance at the CDC said the centers recently released the first scientific report of the incidence of antibiotic-resistant diseases in the United States, estimating a minimum of more than 2 million illnesses and 23,000 deaths annually due to resistant pathogens.

Solomon says antibiotic resistance could be the most complex problem in public health, due to the interactions between pathogens, humans, animals and drugs. Development of antibiotic resistance is a naturally occurring phenomenon, he says, occurring even in the absence of human use of antibiotics.

However, all use of antibiotics contributes to the emergence of resistance in some way. Humans can slow the process by preventing infection, tracking resistance, improving antibiotic stewardship and by developing new drugs, Solomon says. The development pipeline for new antibiotics has slowed though, increasing the importance of the first three strategies.

Solomon notes that excessive antimicrobial use in human medicine plays a role in the emergence of resistant pathogens, saying up to 50 percent of antibiotic use in hospitals is unnecessary or inappropriate. The CDC and other agencies are working to educate physicians and patients, develop benchmarking systems for hospitals and improve prescription policies for better antibiotic stewardship.

Another CDC physician, Dr. Robert Tauxe, who serves as deputy director for the Division of Foodborne, Waterborne and Environmental Infections, encouraged a one-health approach toward the issue of antibiotic resistance, involving human, animal and environmental health. He says antibiotic treatments have been critical in human and veterinary medicine since the 1940s, and resistance has been a challenge nearly as long. The CDC has tracked antibiotic resistance since the 1970s and in 1996 initiated the National Antimicrobial Resistance Monitoring System (NARMS), tracking resistant pathogens in humans, animals and food in cooperation with the USDA and FDA.

Since the 1980s, Tauxe says, outbreaks of resistant pathogens have been linked to livestock. In some cases, resistant bacteria transmitted through the food chain or from contact with animals cause an increase in morbidity and mortality among humans. Other “silent infections” occur when a patient taking an antibiotic for another reason are exposed to pathogens resistant to that antibiotic, leading to disease that otherwise might not occur.

Tauxe offered several examples of resistance linked to antibiotic use in livestock, such as resistant strains of Campylobacter jejuni appearing soon after poultry producers began using the antibiotic ciprofloxacin.

In another example, poultry producers in Quebec voluntarily stopped injecting eggs with Ceftiofur when resistant strains of Salmonella Heidelberg became common in poultry meat. After they stopped using the product, the incidence of resistant pathogens dropped significantly.

In human medicine, Tauxe says it had been routine to treat all cases of shigella with ciprofloxacin, and to use the drug in prophylaxis to prevent the disease among family members or classmates of infected children.  Recently, physicians have moved away from antibiotic use for prevention of shigella infections, stressing sanitation instead, and limited prescriptions to severe cases, and the incidence of resistant pathogens has declined.

Antibiotic resistance presents a substantial challenge, Tauxe says, but it is possible to reverse the trend in many cases if physicians and veterinarians engage in efforts to assure judicious use.

The CDC provides more information on their drug-resistance website.