BOSTON — Researchers have concluded that a Nebraska boy's infection by salmonella bacteria resistant to a widely used pediatric antibiotic came from cattle on his farm.
The report has heightened concerns of public health officials that the routine use of antibiotics by farmers to treat and promote the growth of livestock is reducing the ability of similar antibiotics to cure humans of infections.
"To the extent this could become widespread, it poses a serious problem," said David Bell of the Centers for Disease Control and Prevention in Atlanta. "This particular antibiotic is a drug of choice for treating children, and there is no good alternative approved for them now."
The report, in the edition of the New England Journal of Medicine released today, is the first to identify a case of someone in the United States becoming infected with salmonella resistant to the antibiotic Rocephin. It was found in a 12-year-old boy from western Nebraska who suffered from diarrhea but recovered without complications.
The article brought a harsh reply from the Animal Health Institute, which represents the makers of drugs for animals. The study's findings "do not support the sweeping conclusions of the author," the group said.
Using DNA typing and other molecular-level investigations, researchers from the University of Nebraska Medical School and the CDC concluded that the Rocephin-resistant salmonella found in the boy was the same as that found in the cattle on his family's ranch.
"We don't know exactly how the [salmonella] was transmitted to the child, but we believe it came from the cattle, and so it was ingested by the boy in some form," said Paul Fey of the University of Nebraska Medical School, the study's lead investigator.
The finding comes in the midst of a debate before the Food and Drug Administration over whether to limit the farm use of antibiotics closely related to those used in human medicine. More than a year ago, the FDA proposed guidelines to limit the spread of antibiotic resistance, and late last year it claimed authority to require drug companies to prove any new animal antibiotics won't dangerously increase antibiotic resistance in humans.
Both the livestock and animal pharmaceutical industries have argued that the farm use of antibiotics is necessary and useful and that the science linking use of antibiotics on the farm to drug resistance in humans is inconclusive.
The animal institute also criticized how the new study was conducted, writing that "investigators could not determine how the child acquired the infection or if the resistant strain of salmonella found in one of the cattle samples even originated on the boy's own farm."
Fey acknowledged that his team did not know what drugs the cattle had been given but said public health officials tried to contact the veterinarian treating the cattle and never received a reply. Livestock producers have generally taken the position that what drugs they provide their animals is proprietary information they don't have to share with government officials.
The animal antibiotic Ceftiofur is closely related to Rocephin--also known as Ceftriaxone--and is widely used to treat inflammation of the udder and respiratory diseases in cattle, pigs and poultry.
The many strains of salmonella infect an estimated 1.4 million Americans yearly and approximately 400 die.