Dr. Steven L. Solomon, the director of the C.D.C.’s office of antimicrobial resistance, acknowledged that the report underestimated the numbers, but said that was by design. Researchers were instructed to be conservative and to base their calculations only on deaths that were a direct result of a drug-resistant bacterial infection.

“This is a floor,” Dr. Solomon said. “We wanted the cleanest number, the least subjective number.”

One point of contention has been the extent to which industrial-scale animal farming contributes to the problem of antibiotic-resistant infections in humans. The government has estimated that more than 70 percent of antibiotics in the United States are given to animals. Companies use them to prevent sickness when animals are packed together in ways that breed infection. They also use them to make animals grow faster, though federal authorities are trying to stop that.

The report said that “much of antibiotic use in animals is unnecessary and inappropriate and makes everyone less safe.” It also said that about half of antibiotic use in people is inappropriate.

The 114-page report counts infections from 17 drug-resistant bacteria and one fungus, pathogens that Dr. Solomon said caused an overwhelming majority of drug-resistant bacterial infections in the country. It drew on data from five disease-tracking systems, including a major count of bacterial infections reported in hospitals in 10 different areas across the country. The count of deaths was based on mathematical models — one for each resistant organism.

One particularly lethal type of drug-resistant bacteria, known as CRE, has become resistant to nearly all antibiotics on the market. It is still relatively rare, causing just 600 deaths a year, but researchers have identified it in health care facilities in 44 states.